Compiled by Michael Crestohl, VE2XZ/W1 & KH6KD, Boston MA Internet e-mail: mc@shore.net mc@pcix.com ve2xz@pcix.com from http://www.users.fast.net/~wa3key/collins.html March 18th 1996 ************************************ WA3KEY "VIRTUAL COLLINS RADIO MUSEUM" Collins SSB Amateur Equipment Catalog _________________________________________________________________ [IMAGE] "The" Classic Collins S-Line Station - 1964 _________________________________________________________________ Collins Radio Company, with more than 30 years' experience in research, development and manufacture of distinctive amateur equipment, has dedicated itself to the objective of product excellence. Whatever the field - amateur radio, avionics, commercial broadcasting, space electronics, communication, computation or control - Collins' uncompromising standards of excellence begin with product development and continue through every step of manufacture, quality control and test. Collins' amateur radio equipment has been the standard used by DXpeditions around the world in environmental extremes seldom encountered by the average ham. Collins' single sideband products have long been used by the U.S. military team. During the early years of single side- band communication, the size and weight of the equipment limited its use principally to point-to-point circuits between fixed stations. Continued development following World War 11 has resulted in a wide variety of high performance equipment for airborne, transportable, vehicular and shipboard, as well as fixed station, use. The Strategic Air Command commanders' net, the Strategic Air Command aircraft control net and the Navy Tactical Data System are but a few of the major installations using Collins' single sideband. The Universal Radio Group, latest generation of Collins' SSB equipment, is a highly flexible and sophisticated HF communication design used by the U.S. Armed Forces, NATO and space centers. Collins' research and development, plus the Company's never-ending emphasis on quality control, assure each Collins' amateur equipment owner that he has the most advanced and most thoroughly tested equipment available and that it will retain its value through the years. _________________________________________________________________ [IMAGE] This area is under construction ... please watch your step! On Exhibit ... [IMAGE] 74A-4 Receiver - 1955 [IMAGE] KWS-1 Transmitter - 1955 [IMAGE] KWM-1 Transceiver - 1957 [IMAGE] 75S-3B/3C Receiver - 1967 [IMAGE] 32S-3/3A Transmitter - 1963 [IMAGE] 62S-1 VHF Transverter - 1963 [IMAGE] KWM-2/2A Transceiver - 1959 [IMAGE] S-Line Accessories - 1959 [IMAGE] 30L-1 Linear Amplifier - 1961 [IMAGE] 30S-1 Linear Amplifier - 1959 [IMAGE] 51S-1 General Coverage Receiver - 1959 [IMAGE] 651S-1 General Coverage Receiver - 1976 [IMAGE] KWM-380 Transceiver - 1979 [IMAGE] Arthur A. Collins Biography [IMAGE] Collins Mechanical Filters [IMAGE] Collins Tube Complement Listing _________________________________________________________________ [IMAGE]" The evolution of the Collins emblem ... "Wing" ... "Round" ... "Rockwell" _________________________________________________________________ [INLINE] About the Author [IMAGE] Return to the WA3KEY homepage ______________________________________________________________________ E-mail the "museum" curator [LINK] wa3key@fast.net Copyright © 1996 WA3KEY & Collins Radio Company 1955 &1964
Collins/Rockwell Amateur Products Catalogs reprinted by written permission W.L. Groff - Amateur Products Program Manager This Home Page was created by WebEdit, Saturday, February 24, 1996 Most recent revision Monday, March 11, 1996 ^Z 75A-4 RECEIVER _________________________________________________________________ [IMAGE] THE COLLINS 75A-4 RECEIVER Collins 75A-4 Receiver is designed expressly for Amateur operation on the seven HF bands - 160, 80, 40, 20, 15, 11, and 10 meters. The Receiver retains the time-proven features of the earlier 75A Series; notably, excellent image rejection through the use of double conversion; precise dial calibration and high stability provided by the permeability tuned, hermetically sealed Collins VFO and the crystal controlled first injection oscillator; and ideal selectivity produced by Collins Mechanical Filters. Amateur activity on Single Sideband reveals the need for a receiver designed especially for this type of emission with out sacrificing efficiency when receiving AM, CW or RTTY. The new 75A-4 assures best SSB reception in addition to conventional CW and AM. _________________________________________________________________ 75A-4 SPECIFICATIONS FREQUENCY RANGE - BAND (Meters) RANGE (mc) 160 1.5 to 2.5 80 3.2 to 4.2 40 6.8 to 7.8 20 14.0 to 15.0 15 20.8 to 21.8 11 26.5 to 27.5 10 28.0 to 29.0 10 29.0 to 30.0 SIZE - 10-1/2" high x 17-1/4" wide x 15-1/2" deep. WEIGHT - 35 pounds. RACK MOUNTING - Angle mounting kit available. NUMBER OF TUBES - 22, including rectifiers. AVC TIME CONSTANTS - Rise Time - .01 second Release Time - .1 second (fast) 1 second (slow) AVC CHARACTERISTICS - Audio rise less than 3 db for inputs of 5 to 200,000 uv. SENSITIVITY - 1.0 microvolt for 6 db signal-to-noise ratio with 3 kc bandwidth. IMAGE AND IF REJECTION - Image rejection at center of each band is 50 db or better. IF rejection at center as each band is 70 db or better. AUDIO CHARACTERISTICS - Output - .75 watts with a 3.0 uv signal, 30% modulated. Output impedance - 500 ohms, 4 ohms. Response of audio circuits - +3 db 100 cps to 5000 cps. Distortion--Less than 10% MUTING - Provisions for muting the receiver during key-down operation is provided. A muting voltage of +20 volts must be supplied by the transmitter. FREQUENCY STABILITY (at 14 mc) - Temperature - Less than 1200 cycles drift from 0 to +/-60øC. Warmup drift - Less than 300 cycles after 15 minute operation. Line Voltage - Less than 100 cycles for +10% change. Dial Accuracy - Within 300 cycles after calibration. _________________________________________________________________ Under the hood... [IMAGE] 75A-4 CIRCUITRY GENERAL The 75A-4 amateur band receiver is a dual conversion receiver on all bands except 160 meters where single conversion is employed. The dual conversion scheme employs a fixed high frequency oscillator, crystal controlled, and a variable first intermediate frequency. The signal from a type 70E-24 VFO is beat against the variable IF to produce a fixed 455 KC second intermediate frequency. One stage of RF amplification is employed in the receiver. The passband of the fixed IF (455 KC) is shaped by a mechanical filter stage. A "Q" multiplier stage provides a tunable notch to minimize heterodyne interference. Two more 455 KC IF stages follow the "Q" multiplier. These feed separate detectors for AM or CW-SSB reception. The output of the detectors feed a combination AM and CW type adjustable noise limiter. Three stages of audio amplification follow. The output stage feeds a headset jack and a 500-ohm load or a 4-ohm speaker. A separate AVC amplifier and rectifier are used. Bias for the audio output tube and the RF gain control system is obtained from a separate rectifier. A built-in 100-KC calibration oscillator is included in the set. The passband tuning feature is accomplished by gang tuning the BFO and variable frequency oscillator by means of a metal belt. TUNING All variable tuned stages including the RF stage, the first mixer, the variable IF system and the variable frequency oscillator are operated by the KILOCYCLES dial. This dial is coupled directly to the shaft of the variable frequency oscillator. All other variable tuned circuits just mentioned are tuned by a common platform to which powdered iron slugs are attached. The platform is moved up and down at a linear rate by means of a mechanism which is coupled to the VFO shaft by a system of split gears and metal belts. The receiver uses a unique method of band switching in the RF stage in which only the 80-meter (T-2) and the 160-meter (T-1) coils are tuned by the main tuning mechanism, and coils for 40-10 meters are selected and connected across the 80-meter coil. Varying the inductance of the 80-meter coil varies the total inductance, and therefore the resonant frequency of the tuned circuit in use. RF CIRCUITS A simplified block diagram of the 75A-4 RF system is shown in figure 4-1. The RF stage V-2 feeds the mixer at the carrier frequency of the incoming signal. The first conversion circuit, consisting of a crystal controlled oscillator, V-4 and a mixer tube, V-3, converts the incoming signal to the variable IF frequency of 2. 5 to 1. 5 MC for all bands from 80 meters thru 10 meters. The variable IF is mixed with a signal from the VFO, V-14 and V-15, in the second mixer V-5 where it is converted to a fixed IF of 455 KC. See figure 5-7. A discussion of the individual circuits in the RF portion of the receiver follows: RF STAGE The RF stage uses a 6DC6 pentode. This tube was chosen because of its low-noise, remote-cutoff characteristics. This tube allows greater grid voltage swing without cross-modulation distortion. Individual variable slug-tuned coils are switched into the grid circuit on 160 and 80 meters. On 40-10 meters the coil in use is switched across the 80-meter coil, and varying the inductance of the 80-meter coil tunes the coil for the band in use. The 80-meter trimmer capacitors are not in the circuit on 40-10 meters. One coil, T-7, is used for the 11 and 10-meter bands. Manual tracking is used here employing the ANT TRIM capacitor. C-18. Separate antenna coils are employed on the 10-11-meter coil, the 80-meter coil, and the 160-meter coil. The 160-meter band feeds on thru the first mixer, V-2, into the 2. 5 to 1. 5 MC variable IF coils, which track with the receiver front end, and on into the second mixer V-3. On 80, 40, 20, 15 and the highest frequency 10-meter band the first mixer grid circuit is similar to the RF stage grid circuit with the higher frequency coils being paralleled with the 80-meter coil to produce the tuning for the band in use. On the low 10-meter band and the 11-meter band, capacitors C-32 and C-31 are individually selected to pad the 10-meter coil to these bands. The following table shows the tuning components used in the various bands for each tube circuit. CRYSTAL CONTROLLED OSCILLATOR AND FIRST MIXER The high frequency mixer stage employs a 12AT7 (V-4) in a crystal controlled oscillator circuit to provide a heterodyning signal. In this oscillator circuit the crystal is connected between the cathodes of a dual triode. One section (V-4 pins 6, 7, 8) is a cathode follower amplifier, the other section, a grounded grid amplifier. Feedback voltage is coupled from the plate of one section, which contains a tank circuit resonant at the crystal frequency, to the grid of the other section. The crystal, inserted between the cathodes, acts as a filter. The phase change through the loop is zero and oscillation takes place at the crystal frequency. Crystal oscillator output voltage is coupled to the injection grid of the 6BA7 first mixer. An individual crystal for each band is switched into the crystal oscillator circuit except for 160 meters, where the high frequency oscillator is not used. The crystal oscillator beats with the incoming carrier to produce the first, or variable, intermediate frequency. In this stage, because the crystal frequency is fixed and the incoming carrier frequency may be anywhere in the range of the band in use, the difference frequency produced in the mixer must be tuned by a variable IF system. VARIABLE IF The variable IF covers the range 2. 5 to 1. 5 MC. The system consists of two slug-tuned coils on the same frequency. The first of these coils is capacity coupled to the second which in turn is connected to the grid of the second mixer V-5. L-23, a 5. 7 MC trap is connected between the two coils to remove a spurious response that occurs at 3. 533 MC. VFO AND SECOND MIXER A Type 70E-24 permeability-tuned precision variable frequency oscillator provides the injection voltage to the second mixer V-5. The frequency range of the VFO is 1955KC to 2955KC. This frequency is mixed with the variable IF in V-5 to produce the fixed 455 KC difference frequency which is the frequency of the fixed IF amplifier. MECHANICAL FILTER The mechanical filter uses the principle of magnetostriction to convert electrical energy to mechanical vibration. The magnetostriction transducer input coil is resonated at 455 KC. A nickel wire within this coil vibrates mechanically and transmits this mechanical energy to the first of a series of nickel alloy discs. The mechanical vibration of this first disc is coupled to succeeding discs by means of nickel-wire coupling elements. Biasing magnets at either end of the mechanical filter polarize the filter elements to prevent frequency doubling, in much the same manner as biasing magnets in a headphone prevent the headphone diaphragm from bending in the same direction for both halves of an AC cycle. The mechanical vibration of the last disc is coupled to a magnetostriction transducer element identical to the one used at the input of the filter. By a reverse principle of magnetostriction, the mechanical vibration of the nickel-wire transducer core is converted to electrical energy. Each of the discs employed in the mechanical filter has a mechanically resonant Q exceeding 2,000. Six of these discs are over coupled to produce a mechanically-shaped response curve with a flat top and straight, almost vertical sides. Thus, the filter passes a band of frequencies very little wider than the flat top of the selectivity curve. The mechanical filter furnished with the 75A-4 passes a band of frequencies approximately 3 KC wide and centered on 450 KC, providing an IF selectivity curve ideal for the reception of AM and single-sideband signals. The 3-KC filter is supplied as part of the 75A-4; however, a mechanical filter having similar selectivity characteristics but having a band pass of 800 cycles is available for use in CW reception. A 6-KC filter is available for double sideband reception of AM. The mechanical filters used in the 75A-4 are the plug-in type that plug into a 9 pin miniature tube socket. These are sealed units and must not be tampered with. No external variable tuning is employed. "Q" MULTIPLIER The "Q" multiplier, as used in the 75A-4, is employed only as a rejection filter. In this capacity it performs the same function as the rejection notch of the crystal filter in earlier receivers but does it much better. It is capable of attenuating as much as 40 db, any single audio tone (heterodyne) which may be present within the receiver's passband. The "Q" multiplier consists of a cathode follower amplifier coupled to a regenerative amplifier, the plate load of which is a bridge T-filter. The regenerative amplifier is kept just below the oscillating point by R-36. At this point the plate circuit has a very high Q and provides a very sharp null to frequencies within the receiver passband. REJECTION TUNING capacitor C-72 can shift the null around to any frequency within the passband. The "Q" multiplier is removed from the circuit by turning the 455 KC IF AMPLIFIER The 455 KC IF amplifier consists of V-6 which is associated with the mechanical filter and V-8 and V-9; the latter two are conventional IF amplifiers that contribute nothing to the passband wave shape, which is determined by the mechanical filter. All are 6BA6 tubes. AVC is applied to the grids of all three tubes. AM DETECTOR The AM detector is a conventional diode rectifier excited from IF transformer T-3 and having R-56 and R-57 as its load. The audio from the detector is applied to the noise limiter, V-12, when AM CW SSB selector switch S-3 is operated to AM position. CW-SSB DETECTOR This detector, V-11 is designed especially for SSB reception. It is a mixer type circuit that takes the output of the BFO and mixes it with the output of the 455 KC IF. Tube elements 1, 2 and 3 perform as a cathode follower amplifier. The remainder of the tube is a plate detector, the cathode of which is common with the cathode follower amplifier. The detector greatly reduces the distortion which is generated when a conventional diode detector is used for detecting SSB signals. The audio from the detector is applied to the noise limiter V-12 when S-3 is operated to the SSB position. BFO The BFO V-20, uses a 6BA6 in an electron coupled oscillator whose frequency range is approximately 453-457 KC. The BFO is tuned by means of the knob on the front panel labeled PASSBAND TUNING. The shaft of the PASSBAND TUNING Control is attached by a metal belt to the frame of the variable frequency oscillator which is mounted in a ball and bearing equipped cradle. As the BFO is tuned through its range the VFO is also tuned a like amount. (The shaft of the VFO is prevented from turning by the DIAL DRAG.) Because the actual intermediate frequency is changing, the passband is being shifted and an unwanted signal can be dropped off the edge of the passband while retaining the wanted signal in the passband without changing its pitch. NOISE LIMITER Noise limiter V-12, a 6AL5 tube, couples the audio from the detectors to the first audio stage. The function of the noise limiter is to minimize interference by removing noise peaks which exceed the amplitude of the modulation. It is effective on AM, CW and SSB. Both diode sections of the 6AL5 are required in order to limit both the positive and the negative peaks. During AM reception, a negative voltage is derived across diode load resistors R-56 and R-57. NOISE LIMITER Control R-67 is connected to this source of supply. As a result the cathodes of V-12 assume a negative DC potential which is adjustable by means of the NOISE LIMITER Control, and direct current flows through the diodes (the plates being positive with respect to the cathodes). The AF signal voltage from the receiver is applied to the anode (pin 7) of one section of V-12 through coupling capacitor C-93. This AF signal modulates the DC flowing through this diode section and, as a result, the AF signal appears across cathode resistor R-65. This resistor is common to both diode circuits, therefore the AF signal is superimposed on the DC flowing through the second section of V-12 and appears across load resistor R-63. From this point, the signal is coupled through C-96 and AF GAIN Control R-62 to the audio amplifiers. Any negative impulse that drives the anode of the input diode (pin 7) more negative than the cathode, will cut off the diode, and that impulse will be limited to an amplitude equal to the threshold voltage (as set by the NOISE LIMITER Control). Similarly, any positive impulse that overcomes the threshold potential on the cathode of the second section (pin 5) will cut off that diode, and the positive impulse will be limited. As the NOISE LIMITER Control is turned toward 10, a less negative threshold voltage is applied to the diodes, and more severe limiting results. The threshold voltage at any given setting of the NOISE LIMITER Control varies with the average amplitude of the diode load signal, therefore limiting action automatically adjusts itself. C-97 and R-66 decouple the limiter circuit from the detector circuit. During CW or SSB reception when the carrier is intermittent or absent, the reference voltage is supplied by connecting the NOISE LIMITER Control R-67 through switch S-3 to a value of bias obtained from the receiver bias rectifier. Because of the flat AVC characteristic of the receiver, frequent adjustment of the NOISE LIMITER Control is unnecessary. The noise limiter is made inoperative by applying a value of B+ to the diode plates through R-64 and by grounding the cathodes of V-12 thus insuring that the diode currents cannot be cut off on noise or high modulation peaks. This is done by a switch associated with the NOISE LIMITER Control. C-98 provides a ground path for the audio when S-4 is in the OFF position. AUDIO AMPLIFIERS The audio section consists of two stages of voltage amplification (both halves of the dual triode V-13, a 12AT7) and a 6AQ5 power amplifier. The AF GAIN Control is located in the grid circuit of the first stage. Fixed bias from the bias rectifier is applied to the grid of the power amplifier. The output transformer secondary consists of a 500 ohm winding suitable for driving auxiliary apparatus and a four-ohm winding for use with loudspeaker voice coil and headphones. When a headphone is plugged into the headphone jack J-2, the speaker connection is interrupted and a 10-ohm load resistor is connected in parallel with the headphone to keep the output transformer properly loaded. RF GAIN CONTROL SYSTEM The RF gain control system in the 75A-4 works in conjunction with the AVC system. To control the sensitivity of the set, a source of fixed bias is added to the AVC voltage which is then applied to the AVC controlled tubes. This system maintains the gain distribution constant throughout all settings of the gain control. A low impedance type AVC line is employed. In order to prevent the RF GAIN Control from affecting the characteristics of the line due to loading an RF gain gate is employed to decouple the RF GAIN Control from the AVC line. This gate is in the form of 1/2 of a type 6AL5 twin diode, Y-19. The other half of the tube is employed as a bias rectifier. Bias from this bias rectifier is connected to one end of the RF GAIN Control. The arm of the control is connected to the AVC line through the RF gain gate, V-19 (pins 1 and 7). Advancing the control adds negative bias to the AVC bias and reduces the gain of the tubes connected to the AVC line, namely, V-2, V-6, V-8 and V-9. "S" METER The "S" meter is connected in a bridge circuit between the screen grids of V-6 and V-8 and the cathode of V-8. These are IF amplifier tubes that are furnished with AVC voltage. A reference voltage is developed at the negative terminal of the "S" meter by the cathode current flow of V-8. This reference voltage is adjusted under no-signal conditions to a value equal to that developed at the positive terminal of the "S" meter by the two IF amplifier screen-grid voltages. The presence of a signal in the IF strip causes an AVC voltage to be developed which reduces the screen grid current of the two IF amplifiers, causing the screen-grid voltage on these tubes to increase. This increase in voltage is applied to the positive terminal of the "S" meter to produce an "S" meter reading proportional to the strength of the incoming signal. R41 adjusts the "S" meter sensitivity. AVC SYSTEM A low impedance AVC line is employed to minimize blocking on strong signals. The RF amplifier V-2 and the 455 KC IF amplifiers V-6, V-8 and V-9 are all AVC controlled. A stage of IF amplification V-21, separate from the signal IF amplifier, is employed to amplify the IF signal for rectification for AVC voltage. The IF amplified IF voltage is rectified by 1/2 of V-16, a twin diode. The other half of V-16 is used as an AVC noise clipper. This tube clips sharp noise impulses from the AVC voltage and thus prevents the noise from desensitizing the AVC circuit. A small positive DC voltage is applied to the AVC rectifier through R-86 to produce an AVC delay so that the AVC is ineffective on weak signals. A network of load resistors is switched by switch S-5 to select either fast or slow AVC characteristics. C-110 provides RF filtering for the AVC detector output, R-89, R-91 and R-92 are the detector loads. R-90 and C 112 provide the AVC time constant with R-92 and R-91 modifying the time constant for slow and fast AVC operation. AVC test point J-4 is provided for use in aligning the AVC IF amplifier transformer T-4. Each controlled stage is decoupled from the AVC line by suitable capacitors and resistors to prevent instability because of feedback. CALIBRATOR CIRCUIT The calibrator employs a 6BA6 tube in a crystal controlled oscillator circuit. The fundamental frequency of the oscillator is 100 KC, therefore, a harmonic appears at each 100 KC point over the entire range of the receiver when the calibrator is turned on. C-1 is used to zero beat a calibrator harmonic with a 1500 KC or 1600 KC broadcast station or with WWV at 2. 5, 15 or 30 MC. The calibrator output is coupled to the receiver input by C-5. The calibrator is turned on wherever S-6 is in the CAL position. _________________________________________________________________ 75A-4 / KWS-1 ACCESSORIES [IMAGE] _________________________________________________________________ SC-101 Station Control The SC-101 provides the necessary control functions which, with the necessary antennas and the KWS-1/75A-4 combination, will equip a complete, neat amateur station. In addition to providing the necessary interconnecting harness, the SC-101 contains a beam direction indicator, beam rotation control, phone patch, directional RF watt-meter and remote control for antenna selection. The SC-101 is composed of these units: The 312A-2 includes a 10" speaker, beam direction indicator, directional wattmeter, 24 hour numeral clock, Lumiline lamp, phone patch, power supply for operating relays and terminal board for interconnecting units. Controls on the front panel are a three-position beam control - CCW, OFF and CW; Phone Patch VOX Balance; Phone Patch OFF-ON; Antenna Selector - X, 80, 40, 20, 15, 10; Directional Wattmeter Control - Forward 100, 1000, Reflected 100, 1000; and an ON-OFF switch with indicating light. The Antenna Selector will provide control of any three antennas. Three additional antennas may be controlled with the addition of three relays for which space has been provided. One or two rotators may also be selected in combination with the antennas. One synchro transmitter for tower mounting to feed the beam direction indicator is included with the SC-101. The synchro receiver is an integral part of the direction indicator. The 68Y-1 mounts in any convenient position near the station. It contains the antenna transfer relay, two coax relays for antenna selection, mounting bracket for the directional wattmeter coupler and necessary interconnecting coax cables. Space is provided for mounting three additional coax relays. The 534A-1 includes a metal duct which mounts on the rear of the desk or table and houses all interconnecting cables. Utility AC outlets are provided along the top of the duct. Included is a cable harness for interconnecting the 75A-4/KWS-1, 68Y-1 and 312A-2. Additional standard conduit will be needed in lengths depending on the individual station installation. _________________________________________________________________ 189A-2 Phone Patch This unit provides the necessary apparatus for phone patch operation with the KWS-1 and 75A-4 (or KWM-1). It utilizes a hybrid transformer for proper VOX operation. Output impedance is 600 ohms. Terminal connections are provided on the KWS-1/75A-4 (and KWM-1). Two connections to phone line are all that are necessary. Space for mounting is provided in the 312A-1. The 189A-1 components are a part of the SC-101 and 312B-2 (KWM-1). _________________________________________________________________ 35C-2 Low Pass Filter Collins 35C-2 Low Pass Filter is a 52-ohm three-section low pass filter with approximately 0.2 db insertion loss below 29.7 mc and approximately 75 db attenuation of harmonic emissions at TV frequencies. _________________________________________________________________ Mechanical Filters Collins F455J Series Mechanical Filters are available as accessories for the 75A-4 Receiver. The F455J-05 Filter, bandwidth of 500 cycles, is recommended for CW reception; the F455J-15 (1.5 kc) for RTTY; the F455J-60 (6.0 kc) for AM where interference is not a problem; and the F455J-21 (2.1 kc) and F455J-31 (3.1 kc) for SSB. The F455J-31 is supplied as standard equipment in the Receiver. _________________________________________________________________ 307E-1 Gear Reduction Tuning Knob Provides new ease and accuracy in tuning SSB signals. Operating on a 4 to 1 ratio, it eliminates the need for the Dial Drag control and has no detectable backlash. Simple installation on KWS-1 and all 75A models. Standard equipment on later models of 75A-4 and KWS-1. _________________________________________________________________ 312A-1 Speaker/270G-3 Speaker The 312A-1 Speaker Unit includes loudspeaker and has space for the extra control functions necessary in a complete installation. Unit is furnished with removable perforated steel front panel insert with no cutouts; operator can remove panel and install any control functions such as beam direction indicators, clocks, switches, etc. A 10" speaker is sub-mounted behind the front panel and a Lumiline lamp above. Rear of the unit is open and across the bottom is a terminal strip. The 270G-3 cabinet and 10" PM speaker assembly is attractively finished to match the 75A-4 Receiver. _________________________________________________________________ 302C-1 and -2 Directional RF Wattmeter This wattmeter measures forward and reflected power in a 52-ohm coaxial transmission line over the frequency range of 2-30 mc. Scale ranges of 0-100 and 0-1000 watts are provided. The 302C-1 consists of indicator unit and coupler unit, the 302C-2 of coupler and unmounted meter and selector switch for custom installation. 180S-1 Antenna Tuner This is an antenna matching device that can be configured as either an L or pi-network. Power 1-KW, Frequency range 3-30 Mc. 136C-1 Noise Blanker This is an RF noise blanker for the 75A-4. _________________________________________________________________ Return to Collins Radio Index E-mail the "museum" curator wa3key@fast.net Copyright © 1996-WA3KEY & 1957-Collins Radio Company This Home Page was created by WebEdit,Thursday, February 22, 1996 Most recent revision Thursday, February 22, 1996  KWS-1 TRANSMITTER _________________________________________________________________ [IMAGE] THE COLLINS KWS-1 TRANSMITTER The most advanced design features ever offered in an Amateur transmitter are incorporated in the KWS-l. Unprecedented compactness is achieved without crowding; the exciter and RF power amplifier are housed in a single receiver-size cabinet which can be placed on the operating desk or mounted on top of the power supply cabinet. Collins engineering plus extensive on-the-air operation account for the KWS-1's reliability and optimum performance in CW, AM, and SSB operation. Circuit applications and components which have been proved in preceding Collins equipment are retained in the design of the KWS-1 - 70E VFO, Pi-L output network, extremely accurate VFO dial, and the Collins Mechanical Filter, to mention a few. The frequency generating system provides stable output on the desired frequencies with minimum low order mixer crossover products and spurious responses. VFO operation is provided in amateur bands from 3.5 to 30 megacycles, with a dial calibration of 1 kc per division on all bands. Single conversion is used on the 80 meter band and dual conversion is used on all higher bands. Maximum overall stability is obtained by using an extremely stable variable oscillator and crystal controlled high-frequency oscillators and BFO. A permeability tuned, hermetically sealed VFO is used to provide a stable and accurately calibrated signal source. A new PTO oscillator, Type 70E-23, was designed to give stability comparable to that of Collins 75A-4 Receiver. By using the Mechanical Filter, the Single Sideband generator provides more than 50 db rejection of the unwanted sideband and limits the audio passband to 3000 cps. By use of the balanced modulator in conjunction with the Mechanical Filter, the carrier can be reduced more than 60 db. The third order distortion products are down approximately 35 db. _________________________________________________________________ KWS-1 SPECIFICATIONS POWER AMPLIFIER INPUT - 1 kw peak envelope power on SSB, 1 kw CW operation. Equivalent to 1 kw on AM when using narrow bandwidth receiver. RF OUTPUT IMPEDANCE - 52 ohms. MAXIMUM PERMISSIBLE STANDING WAVE RATIO - 2.5 to 1. AMATEUR BANDS COVERED - 80, 40, 20, 15, 11, 10 meters. FREQUENCY RANGE - BAND RANGE 80 3.0 - 4.0 40 7.0 - 8.0 20 14.0 - 15.0 15 21.0 - 22.0 11 26.4 - 27.4 10 28.0 - 29.0 10 29.0 - 30.0 EMISSION - SSB, AM carrier plus one sideband, CW. FREQUENCY CONTROL - 70E-23 Master Oscillator. HARMONIC AND SPURIOUS RADIATION - (Other than 3rd order distortion products.) Intra-channel radiation is at least 50 db down. All spurious radiation is at least 40 db down at the output of the exciter. The second harmonic is at least 40 db down and all other harmonics are at least 60 db down. FREQUENCY STABILITY - After 15 minutes warm-up, within 300 cps of starting frequency. Dial Accuracy: 300 cps after calibration. AUDIO CHARACTERISTICS - Response: +/-3 db, 200 to 3,000 cps. Noise and hum: 40 db or more below reference output level. Input: .01 volts for rated power output. DISTORTION - SSB, 3rd order products approximately 35 db down at 1 kw PEP input. MICROPHONE INPUT - Will match high impedance dynamic or crystal. PHONE PATCH INPUT IMPEDANCE - 600 ohms, unbalanced to ground. WEIGHT - 210 pounds (both units). DIMENSIONS - 40-1/2" high, 17-1/4" wide, 15-1/2" deep (both units). RACK MOUNTING - Angle bracket kits available for RF unit and power supply. TUNING CONTROLS - Bandswitching, frequency selector, PA tuning, PA loading. OTHER CONTROLS - Filament power, plate power, filament adjust, PA bias adjust, tune-operate, multimeter switch, VOX speaker gain, VOX speech gain, band change, audio gain, sideband select, emission selector, dial lock, zero set. ACCESSORIES REQUIRED - High impedance microphone, telegraph key, 52 ohm antenna. POWER SOURCE - 230 v, 3 wire, 50/60 cycle, single phase, grounded neutral; or 115 v, 2 wire, 50/60 cycle, single phase. 1500 W 1 kw input CW. _________________________________________________________________ Under the hood... [IMAGE] KWS-1 CIRCUITRY While the KWS-1 Transmitter is capable of AM, SSB, FSK, or CW operation, its design emphasis on SSB perhaps warrants description in the SSB condition. Referring to the block diagram, the audio input is fed through a two-stage amplifier to a cathode follower (1/2 12AT7). This cathode follower matches the audio signal impedance to that of the balanced modulator. The output of the low frequency oscillator is also fed into the balanced modulator. The output of the balanced modulator will contain both upper and lower sideband signals with the carrier balanced out. By selecting the proper LFO frequency, either the upper or lower sideband signals can be placed in the passband of the 250 kc Mechanical Filter. At the output of the Filter, one of the two sidebands appears. The carrier and opposite, or undesired, sideband will be greatly suppressed. The output of the Filter is fed to the first mixer, (12AT7) and here it is mixed in a dual triode with the VFO output. The output of the mixer is fed through a two-stage linear amplifier with five Hi-Q tuned circuits. These two stages (6BA6's) and the five coils provide sufficient gain and selectivity to give an output signal in the 80 meter band essentially free of spurious signals. On 80 meters, the signal is then fed to the driver stage which is a pair of 6CL6's. The output of the 6CL6's is very conservatively rated at 3 watts PEP. This is sufficient output to drive the linear Class AB1, 1 kw PEP power amplifier. On all bands except 80 meters, the output of the two-stage RF amplifier is fed to a second mixer. Here it is mixed with a crystal oscillator. The proper crystal is selected by the bandswitch to give the correct output frequency for the desired band. The output of the mixer is fed to an RF amplifier with three Hi-Q tuned circuits. Again sufficient gain and selectivity is provided to give an output signal on the desired band that is essentially free of spurious signals. The output of this stage is then fed to the pair of 6CL6's in the driver stage. The Linear RF Power Amplifier uses two 4X250B's in Class AB1 operation. The 4X250B's are used because of their superior performance as linear amplifiers, their small size, and lower plate voltage requirements. Negative RF feed-back is employed to improve linearity. Third order distortion products are reduced to approximately 35 db below either tone in a two-tone test. The speaker anti-trip circuitry is in the audio section of the exciter. Here a differential-type circuit is provided that compares the audio level from the speaker -as picked up by the microphone- with the audio level from the receiver output circuit. When this circuit is balanced, loudspeaker signals picked up by the microphone will not actuate the VOX relay. However, the operator speaking directly into the microphone will actuate the VOX relay. When operating AM, the output of the LFO is fed around the Mechanical Filter and provides operation with full carrier and one sideband. It is possible in this position to vary the amount of reinserted carrier, thus providing Single Sideband reduced carrier operation. CW operation is provided also by feeding the output of the LFO around the Mechanical Filter and by blocked-grid keying of the 6BA6 amplifier following the first mixer and the output stage. POWER SUPPLY High and low voltage power to the KWS-1 Transmitter is provided by the 428A-1 Power Supply, contained in a single cabinet 17-3/8" wide, 30" high, and 15-1/2" deep. The 428A-1 Power Supply provides filament power and filtered dc voltage to the plates and screens of the 4X250B Power Amplifier tubes. The 428A-1 also includes a plate contactor, fuses, primary switch, suitable interlocks, and a blower to provide cooling air for the Power Amplifier tubes. The Low Voltage Supply consists of a single-phase full wave rectifier and filter supplying dc plate voltage to the exciter, a second full wave rectifier which furnishes negative dc voltage for bias and blocked grid keying of the transmitter, and filament power for the exciter and oscillator tubes. A fuse is provided in the primary power line for equipment protection. CIRCUIT DESCRIPTION SSB SIGNALS The audio signal is fed from the microphone jack J101 on the front panel through a two-stage amplifier into a cathode follower audio output stage. The cathode follower matches the audio signal to the 1N67A diode balanced ring modulator. The output of a 250-kc oscillator is amplified and fed into the balanced modulator. The output of the modulator contains both upper and lower sidebands, but the carrier is attenuated by more than 50 decibels. The signal is fed through a mechanical filter, the input of which is series tuned to match the low impedance of the balanced modulator. The FL101 Mechanical Filter has an output containing either the upper or lower sideband, depending upon the selection of the operator. The carrier and undesired sideband are greatly suppressed, or, for all purposes of signal consideration. are eliminated. The output of the FL101 Mechanical Filter is parallel tuned to match the high impedance of the first mixer grid. In addition to accepting output signals from the FL101 filter, the first mixer also accepts signals from the vfo. The mixer plate circuit contains a special feedback network which provides an additional 20 decibels of attenuation to undesired vfo signals appearing in the plate circuit. The desired output of the mixer is passed through two stages of linear amplification, including five high "Q" tuned circuits. The tuned circuits provide sufficient gain and selectivity to produce essentially spurious-free signals in the 80-meter band. At this point, the 80-meter signals are fed directly into the paralleled driver stages, while the frequencies of the 40, 20, 15, 11, and 10-meter bands require further conversion. These signals are fed into a second mixer, which also receives an input from a crystal oscillator. The oscillator signal is selected by the BAND CHANGE control to provide correct output frequencies for the desired band. The conversion frequency output of the second mixer is fed through two stages of r-f amplification, including three high "Q" tuned circuits to produce a signal which is again, essentially spurious-free. The amplified signal is then fed into the 6CL6 driver stages. The output of the drivers is fed directly into the Power Amplifier. The Power Amplifier is designed for linear class AB1 operation with individual tuning and loading controls in the final amplifier output circuit. Grid-plate neutralization is included to provide improved stability of operation. An r-f feedback system is used to permit operation with lower distortion. An Automatic Load Control circuit is also included in the Power Amplifier, however, a complete analysis of this circuit is included in the detailed circuit description. CIRCUIT DESCRIPTION AM SIGNALS For AM signals, the output of the 250-kc oscillator is reinserted at the output of the mechanical filter to provide operation with carrier and one sideband. By adjustment of the CARRIER LEVEL control, it is possible to vary the amount of carrier reinserted and produce the proper relationship between the sideband and the carrier. CIRCUIT DESCRIPTION CW SIGNALS CW operation is produced by reinserting the 250-kc oscillator signal at the output of the mechanical filter, as in AM operation, and by grid-block keying of the first mixer and the driver stages. The EMISSION control eliminates exciter circuits unnecessary for cw signals. A wave shaping network is included to reduce transients in the cw output. CIRCUIT DESCRIPTION FSK SIGNALS Although a 600-ohm audio input circuit is available for use with an external phone patch circuit, it is also possible to feed an external audio FSK oscillator into this circuit to provide for carrier shift FSK operation. With the EMISSION switch in the SSB position, the mark and space frequencies of the audio oscillator produce two r-f voltages in the exciter output, spaced by the correct amount for all bands. _________________________________________________________________ KWM-1 TRANSCEIVER _________________________________________________________________ [IMAGE] THE COLLINS KWM-1 TRANSCEIVER The KWM-1 covers the frequency range of 14-30 mc with an input of 175 watts PEP or SSB. In addition to SSB emission it also utilizes the VOX circuits for break-in CW operation with a built-in monitor. The bands are covered in 100 kc segments with a total of 10 such segments. A box that plugs into the front panel contains the 10 injector oscillator crystals. A standard crystal complement is furnished as detailed in the specifications. For other selections such as MARS or commercial frequencies, extra crystal boxes with the proper crystal complement can be obtained. The front panel meter acts as an S-meter on receive and as the tuning meter on transmit. Frequency stability, receiver sensitivity and selectivity are outstanding. Maximum convenience in switching between mobile and fixed station is built in. For mobile installation the unit plugs into the mounting rack. The power plug, antenna coax connector, and speaker, are in one plug and connect automatically. Two knobs tighten to hold the unit securely in place. For fixed installations a separate speaker jack is provided. Power connections and antenna coax connection would be made through the same plug used for mobile installation. A 100 kc crystal calibrator is included. _________________________________________________________________ KWM-1 SPECIFICATIONS RF POWER INPUT: 175 watts SSB PEP or 160 watts CW. OUTPUT IMPEDANCE: 52 ohms with not more than 2.5:1 SWR. POWER SOURCE: 115 vac 50-60 cps, 12 vdc, or 28 vdc POWER INPUT: Filaments 5.25 a at 12 v; B+ and Bias: Transmit: 800 v at 200 ma; 265 v at 210 ma; - 50 to -80 v at 3 ma Receive: 290 v at 170 ma. SIZE: Transceiver - 6-1/4" h, 14" w, 10" d AC Power Supply - 6-1/4'' h, 7-5/8" w, 10" d DC Power Supply - 7-19/32" h, 10-1/8" w, 5-3/4" d Speaker Cabinet - 6-1/4" h, 7-5/8" w, 10" d WEIGHT: Transceiver - 15 Lbs. AC Power Supply - 25 Lbs. DC Power Supply - 15 Lbs. Speaker Cabinet - 5 Lbs. FREQUENCY RANGE: 14-30 mc continuous. Choice of any ten 100 kc bands by crystal switch. Standard complement of crystals: 14.0 - 14.1 mc CW 14.2 - 14.3 mc SSB 14.9 - 15.0 mc calibration with WWV 21.0 - 21.1 mc CW 21.3 - 21.4 mc SSB 21.4 - 21.5 mc SSB 28.0 - 28.1 mc CW 28.1 - 28.2 mc CW 28.5 - 28.6 mc SSB 28.6 - 28.7 mc SSB FREQUENCY CONTROL: 70K-1 Permeability Tuned VFO HARMONIC AND SPURIOUS RADIATION: Carrier suppression -50 db, unwanted sideband 50 db, oscillators and mixer products -50 db, second harmonic -50 db, 3rd order products 30 db. FREQUENCY STABILITY: After 10-minute warm-up, within 100 cps. Reset within 1 kc throughout range. AUDIO CHARACTERISTICS: Response 300 - 3,000 cps noise 40 db below one tone carrier; transmitter input designed for high impedance crystal or dynamic mike. PHONE PATCH IMPEDANCE: 600 ohms unbalanced to ground. CIRCUIT PROTECTION: Primary fuses. ACCESSORIES REQUIRED: Hi-Z Dynamic or Crystal Microphone and/or telegraph key, antenna, loudspeaker and/or headphones, 516E-1 dc and/or 516F-1 ac power supply POWER SOURCE: 115 vac 50-60 cps; 12 vdc; 28 vdc. RECEIVER SENSITIVITY: 1.0 uv for 6 db S/N ratio with 3 kc bandwidth. NUMBER OF TUBES: 24 plus 2 rectifiers in ac power supply. NUMBER OF TRANSISTORS: 6 in dc power supply. _________________________________________________________________ Under the hood... [IMAGE] KWM-1 CIRCUITRY TRANSMITTING FUNCTION The audio amplifier (V19) consists of a two-stage amplifier and a cathode follower (V18) driving a ring-type balanced modulator, which feeds a 455 kc Mechanical Filter. The 455 kc signal is heterodyned by V6 to a band pass IF frequency of 3.9-4.9 mc by means of the VFO. The band pass IF frequency is then heterodyned by V5 to the desired output frequency by means of crystals. Ten such crystals can be selected from the panel, each allowing operation over a 100 kc portion of the spectrum. The output frequency is amplified by two amplifier stages (V3 and V4) and the driver stage (V2) and applied to the grids of the two 6146's in parallel (V23 and V24). The output circuit consists of a Pi-L network and will match 52-ohm antennas with up to 2.5:1 SWR. A self-adjusting dual time constant ALC circuit effectively provides higher average talk power. VOX and speaker anti-trip circuits are an integral part of the design. CW operation is obtained by feeding a keyed audio tone into the transmitter audio circuits. A portion of this audio tone is fed to the receiver audio circuits for monitoring. RECEIVING FUNCTION During transmit or receive, tubes not being used are biased to cutoff. A received signal is fed through the antenna change-over relay to the grid coil of V4. Since V5 and V3 are cut off, the signal passes through V4 to V7. This tube heterodynes the signal with a crystal oscillator to produce a signal in the range of 3.9-4.0 mc. With V6 and V5 cut off, the signal will pass through the IF transformer to V8. This mixer heterodynes the IF against the VFO to produce a signal at 455 kc. The signal passes through the Mechanical Filter to the grid of V13. Since V18B is cut off, no BFO voltage is fed to the balanced modulator so it is inoperative even though still connected to the Mechanical Filter. The signal passes through V13 and V14, the receiver fixed IF amplifier, and is detected by V15. V12 is the AVC rectifier. The detected signal is amplified by V16 and V17 with audio outputs of 4 ohms and 500 ohms available. V1, a 100 kc calibrator, furnishes calibration signals for the receiver dial, with provision for comparison with WWV on 15 mc. _________________________________________________________________ ELECTRICAL CHARACTERISTICS The KWM-1 receives or transmits (on the same frequency) SSB or CW signals in the 14.0 to 30.0 mc range. Blocking-bias control circuits switch from receive to transmit function by disabling some of the tubes. The vox and anti-trip circuits permit voice operation on SSB and break-in operation on CW. RECEIVE-TRANSMIT COMMON CIRCUITS Circuits common to both receive and transmit functions are: Receive-transmit amplifier V4 and its tunable grid and plate circuits. (These are gang tuned with other circuits tuned by EXCITER TUNE control on front panel.) The 3.9- to 4.0-mc band-pass i-f transformer T1. Mechanical filter FL1. High-frequency oscillator V11. Beat-frequency oscillator V9. Variable frequency oscillator V22. Control circuits. RECEIVE CIRCUITS ... R-F CIRCUITS Signals from the antenna are connected from J5-A1 through contacts of relays K1 and K2 to the grid of r-f amplifier V4. Grid circuit (L1, C13, and C15) and plate circuit (L3, C10, and C21) are tracked and ganged to the EXCITER TUNE control on front panel. Output from V4 and high-frequency oscillator signal from V11 are fed to the first receiver mixer (V7). I-F CIRCUITS Difference frequency (3.9 to 4.0 mc) is coupled through i-f transformer T1 to the receiver second mixer (V8). The 3.9- to 4.0-mc signal is mixed with the 3.445- to 3.545-mc vfo signal in V8 to produce the 455-kc i-f signal. This i-f signal is coupled through the mechanical filter FL1 to the grid of the receiver i-f amplifier (V13). A two-stage i-f strip, consisting of V13, and V14, amplifies the 455-kc signal and applies it to the agc rectifier (V12A) and the product detector (V15). A-F CIRCUITS Beat-frequency oscillator signal is applied to the product detector which mixes the two signals to produce demodulated audio signal. The audio signal is filtered by L17, C86, C89, C88, and C77 and amplified by V16A and V17 for application to phone patch, speaker, and headphone circuits. Negative voltage, developed by V12A, provides automatic gain control to receiver amplifier circuits. The R.F. GAIN control (R116) is used to set the level of operating gain for all receiver r-f and i-f amplifier stages. Audio output level is controlled by A.F. GAIN control R79. TRANSMIT CIRCUITS ... A-F CIRCUITS AND SSB GENERATION Microphone signal is amplified by V19A and V19B and applied to cathode follower V18A. Signal level applied to the cathode follower is controlled by MIC. GAIN control R92. Output from the cathode follower is filtered (by L18, C96, and C98) and applied to the diode-ring balanced modulator (CR1 through CR4) consisting of four matched 1N67's. Carrier energy is supplied from the bfo through an isolation stage (V18B) to the balanced modulator. Output of the balanced modulator (with carrier balanced out) is applied to mechanical filter FL1 which passes only the lower sideband energy to the first transmit mixer (V6). R-F CIRCUITS Mixer V6 combines the 455-kc sideband signal and the 3.445- to 3.545-mc vfo signal to produce a 3.9- to 4.0-mc output. The 3.9-4.0 mc signal is amplified by V3 and applied to second transmit mixer V5. Tuned circuits T1 and T2, are bandpass transformers. Mixer V5 combines the 3.9- to 4.0-mc signal with the high-frequency oscillator signal and inverts the side-band to produce the desired upper sideband output frequency. This output signal is amplified by V4 and V2 and applied to the final amplifier. Both driver (V2) and final amplifier (V23 and V24) stages are neutralized by the capacity-bridge method, and negative feedback is coupled to the cathode of the driver to improve linearity. The Pi-L power-output circuit consists of C42, L10, L11, C43 and C44, and L12. Output power is connected from L12 through contacts of K1 and connector J5-A1 to the antenna. CONTROL CIRCUITS ... VOX AND ANTI-TRIP CIRCUITS Vox and anti-trip circuits operate as follows: A portion of the audio voltage developed across R93 (in output of V19B) is amplified by V20A and rectified by V21A. The positive d-c output of V21A is applied to the grid of V16B causing V16B to conduct current and actuate vox relay K2. Contacts of K2 switch the high-voltage plate power supply into operation, (on d-c supply only; these contacts are jumpered in the a-c supply) disconnect the antenna from V4 grid, and energize relays K1 and K3. Relay K1 switches the meter M1 from receiver S-meter circuits to transmitter multimeter circuits and switches antenna connections so that receiver input is grounded and transmitter output is connected from L12 to the antenna through J1. Relay K3 applies screen voltage to the power amplifier, and plate voltage to V18A turns on transmitter tubes (V2, V5, V6, and V18B) and turns off receiver tubes (V7, V8, V12, V13, V14, and V15). The anti-trip circuit provides a threshold voltage to prevent loud-speaker output (picked up by the microphone circuits) from tripping the KWM-1 into transmit function. Some of the receiver audio output voltage is connected through C116 and R115 to the anti-trip rectifier (21). Negative d-c output voltage from V21B, connected to the grid of V16B, provides the necessary anti-trip threshold. ANTI-TRIP control R115 adjusts the value of the anti-trip threshold so that loud-speaker output will not produce enough positive d-c output from the vox rectifier to exceed the negative d-c output from V21B and cause V16B to actuate K2. However, speech energy into the microphone will cause the positive vox voltage to overcome the negative anti-trip voltage and produce the desired action of K2. MANUALLY OPERATED SWITCHES VOX GAIN control R93 is ganged mechanically to switch S3 which may be used for transmit-standby manual control if desired. When R93 is turned down through minimum, S3 closes and shorts the cathode of V16B to ground, causing the tube to conduct and actuate the switching relays. (Refer to figure 3-1.) As the EXCITER TUNE control is adjusted near 14.0 mc, 21.0 mc, or 30.0 mc, S5 connects pins 15, 16, or 17 (respectively) of J5 to ground to operate any desired combination of antenna selecting relays. Crystal selector switch S1 selects the proper crystal for high-frequency oscillator V11 to put the KWM-l in the desired 100-kc portion of its operating range. Switch S2 selects metering function for M1 when the EMISSION SWITCH S4 is in SSB, CW, or TUNE position. EMISSION SWITCH section S4A applies PA screen voltage through PA SCREEN switch S6 in all positions except OFF. In TUNE position, the screen voltage is reduced through a voltage divider R154 and R155. Section S4B turns on crystal calibrator V1 in CAL position and turns on tone oscillator V20B in CW and TUNE positions. Section S4C removes cutoff bias from V19B when in SSB, TUNE, and LOCK KEY positions. Section S4D reduces input of V18A and V16A when in SSB and CAL positions and grounds alc voltage in CW, TUNE, and LOCK KEY positions . Section S4E grounds microphone input in CW position and reduces input to V18A and V16A when in TUNE and LOCK KEY positions. Switch S4G, mounted on rear of S4, turns on all low voltage supplies in all positions except OFF. OSCILLATOR CIRCUITS The crystal-controlled bfo provides 455-kc (nominal frequency) carrier to the balanced modulator and bfo injection to the frequency product detector. Its crystal is selected to fall at the -20-db point on the high-frequency skirt of the mechanical filter band pass. The vfo is a series-tuned type circuit. Its operating frequency of 3.445 to 3.545 mc is controlled by a permeability-tuned coil. The high-frequency oscillator (V11) is crystal controlled by one often crystals selected by the crystal selector switch on the front panel. These crystals may be selected to operate at any frequency in the operating range. The tone oscillator (V20B) is an RC phase shift type which supplies a 1-kc tone for tuneup and CW operation. The 100-kc crystal calibrator (V1) supplies calibration check points for calibrating the receiver dial. _________________________________________________________________ KWM-1 ACCESSORIES [IMAGE] _________________________________________________________________ 516E-1 POWER SUPPLY The 516E-1 Power Supply operates from 12 vdc. A cable connects directly to the mounting tray from a terminal strip on the front. The Transceiver power is automatically connected as it plugs into the mounting tray. The 516E utilizes six power transistors as switching elements at 600 cps, eliminating vibrators and rotating machinery. A similar supply is available for 28-volt operation. _________________________________________________________________ 516F-1 POWER SUPPLY The 516F-1 AC Power Supply operates from 115 vac, 50-60 cps, and provides all necessary voltages for operation of the KWM-l. Both supplies are designed with dynamic regulation for maximum SSB power efficiency. _________________________________________________________________ 312B-2 SPEAKER CONSOLE The 312B-2 Speaker Console has a 5" x 7" speaker, built-in 189A-1 phone patch and 302C-1 directional RF wattmeter, all mounted in a matching cabinet for fixed station use. The 312B-1 Speaker includes a 5" x 7" speaker sub-mounted in matching cabinet like the 312B-2. Space behind panel provides for installation of controls, switches, etc. _________________________________________________________________ MOBILE MOUNT This bracket will greatly facilitate mounting the KWM-l under an automobile dashboard, providing snap-in and snap-out installation and removal of the transceiver. The bracket arms fold out of the way after removal of the KWM-1. A number of different bracket adapters are available - ask your distributor for information on your automobile. _________________________________________________________________ CRYSTAL PLUG-IN UNITS These fill requirements for other than the 10 basic 100 kc bands supplied with the KWM-1. These units plug into the front panel, and can contain up to 10 CR-18 HF oscillator crystals and a rotary tap switch for crystal selection. _________________________________________________________________ DX CONVERSION ADAPTER This unit replaces the crystal box and automatically changes transceiver operation to separate transmitter and receiver functions. This enables tuning of the receiver outside the band for DX and provides a choice of several crystal-controlled transmitter frequencies in the band. The adapter allows duplex operation in any one band in the 14-30 mc range. _________________________________________________________________ 75S-3B/3C RECEIVER _________________________________________________________________ [IMAGE] THE COLLINS 75S-3B/3C RECEIVER The Collins 75S-3B is a versatile receiver with exceptionally sharp selectivity and operation in any of three modes - SSB, CW and RTTY. AM reception is provided, and the passband can be optimized by the installation of an optional 3.1, 4.0 or 6.0 kc Mechanical Filter. Two CW mode switch positions with optional plug-in filters offer up to three degrees of selectivity in the CW/SSB function. The 75S-3B combines all Collins' proven qualities in design engineering and workmanship with unexcelled frequency stability and these other features: REJECTION TUNING by a single control provides 50 db nominal rejection of unwanted heterodynes and carriers. VARIABLE BFO results in additional convenience to CW and RTTY operators. The variable BFO can be utilized in either the CW or SSB mode. OPTIONAL 500, 800 or 1500 cps Mechanical Filter offers sharp selectivity for CW. An optional 200 cps crystal filter is also available. 2.1 KC MECHANICAL FILTER assures sharp skirt selectivity and optimum passband for SSB. Background noise is effectively reduced by restricting bandwidth to only that required for communication. It can also be used for CW and RTTY. ZENER REGULATED OSCILLATORS provide increased stability and less variance due to line voltage changes. AGC CONTROL KNOB disables AGC or selects two AGC decay time constants. This permits choice of AGC characteristics to suit operating conditions. CONCENTRIC RF AND AUDIO GAIN CONTROL arrangement on the 75S- 3B receiver offers increased operating convenience. AUDIO OUTPUT of 3.0 watts assures adequate speaker levels. The 75S-3B Receiver can be combined with the 32S-3 Transmitter and 312B-4 Station Control to make a completely integrated station. The 75S-3B, when used with the 32S-3, is capable of transceiver-type operation with the receiver PTO controlling the transmitting frequency. The 75S-3B can also be used conveniently with the Collins KWS-1, as well as the Collins KWM-1 or KWM-2 Transceiver. Coverage outside the amateur bands, or additional 10 meter- band frequency coverage, can be obtained by plugging in the appropriate crystals. The pitch for CW reception can be varied by turning the BFO control on and adjusting the knob for the most pleasing beat note, with the desired signal centered in the filter passband. The calibration marks can be used to shift from high mark to low mark when you are copying RTTY. When the BFO knob pointer is at the 0 reference mark, the BFO frequency is approximately the same as crystal BFO in USB position. With the knob in the off position, the crystal BFO is in operation. RTTY operation requires a conventional converter and printer. Fine tuning in this mode is easily accomplished with the variable BFO. Also available is the 75S-3C, providing extended range coverage. It is identical to the 75S-3B except that an additional HF crystal board and front panel selector switch are included. The board for additional crystals is located on the top of the chassis and the standard group of amateur band crystals is mounted in the board on the underside of the chassis. _________________________________________________________________ 75S-3B/3C SPECIFICATIONS FREQUENCY RANGE: 3.4-5.0 mc and 6.5-30 mc, for the following bands: 80 meters - 3.4-3.6 mc, 3.6-3.8 mc and 3.8-4.0 mc. 40 meters - 7.0-7.2 mc and 7.2-7.4 mc. 20 meters - 14.0-14.2 mc and 14.2-14.4 mc. WWV - 14.8-15.O mc. 15 meters - 21.0-21.2 mc, 21.2-21.4 mc and 21.4-21.6 mc. 10 meters - 28.5-28.7 mc. MODE: Selectable USB, LSB, CW or AM. TYPE OF SERVICE: Selectable single sideband, CW, RTTY and AM continuous. POWER REQUIREMENTs: 115 v, 50-60 cps. Power consumption is approximately 85 watts. Power can be provided by an external supply which delivers 185 v dc at 125 ma and--62 v dc at 5 ma. Filament power can be ac or dc as follows: 6-7 v at 5.5 amps, 12 4 v at 2.75 amps or 24-28 v at 1.4 amps. HARMONIC AND OTHER SPURIOUS RESPONSE: Image rejection better than 50 db. Internal spurious signals below 1 uv equivalent antenna input. AUDIO NOISE LEVEL: Not less than 40 db below 1 watt. AMBIENT TEMPERATURE: 0 -50 C. AMBIENT HUMIDITY RANGE: 0%-90%. ALTITUDE: 0-10,000 ft. PROTECTIVE DEVICES: The ac line has a 1 amp SB fuse. SIZE: Receiver with feet - 14-3/4" W, 7-3/4" H, 12-1/2" D. WEIGHT: 20 Lbs. CALIBRATOR: 100 kc crystal. FREQUENCY STABILITY: Within 100 cps after warm-up. CALIBRATION ACCURACY: 1 kc after midband calibration. BACKLASH: Not more than 50 cps. VISUAL DIAL ACCURACY: 200 cps on all bands. SENSITIVITY: 0.5 uv for 10 db signal-plus-noise-to-noise ratio in SSB mode. SELECTIVITY: SSB - 2.1 kc, 2:1 shape factor. CW - two switch positions and sockets; no filters supplied. AM--5 kc. Optional filters for 0.2, 0.5, 0.8, 1.5, 3.1, 4.0 or 6.0 kc are available. VARIABLE BFO: Tunes 452.35-458.35 kc. AUTOMATIC GAIN CONTROL: AGC threshold - 1.5-3.0 uv, 1.5 nominal. Selectable AGC time constant, Fast, Slow and Off. Attack time is 1 millisecond in both Fast and Slow. Fast release time is 190 milliseconds. Slow release time is 600 milliseconds. AUDIO OUTPUT LEVEL: 1 watt at AGC threshold, 3 watts maximum. ANTENNA INPUT: 50 ohms nominal +/-50%. AUDIO OUTPUT REQUIREMENTS: Speaker - 3-4 ohms. Headphones - 500 ohms or higher. AUDIO DISTORTION: Not more than 10% at 1 watt. MUTING: Receiver silenced during transmit. _________________________________________________________________ Under the hood... [IMAGE] 75S-3B/3C CIRCUITRY Double conversion is used with injection voltage for the first conversion provided by a crystal-controlled oscillator. A bandpass if 200 kilocycles wide is used to couple the first and second mixers. Injection voltage for the second mixer is furnished by a vfo with a tuning range of 200 kc. The 455-kc output frequency of the second mixer is coupled through the if. system to separate AM and SSB detectors . Injection voltage for the product detector is provided by either a crystal-controlled bfo or a tunable bfo. The 75S-3C is electrically identical to the 75S-3B, except that it is equipped with an extra hf crystal mounting board on the chassis, a crystal board selector switch on the front panel, and associated components. RF and Mixer Circuits The rf amplifier grid, high-frequency mixer grid, and crystal oscillator plate circuits are resonated by slug- tuned coils. The slugs are mechanically ganged and linked to the PRESELECTOR tuning knob. The required tuning ranges of these circuits are obtained by switching appropriate values of fixed capacitance in parallel with the coils. The total 3.4- to 30-mc tuning range of the receiver is divided into five segments for band switching purposes, as noted in table 2-1. The tuned-circuit LC ratio is thereby varied within appropriate limits for each of the five segments. Signals within the particular 200-kc band selected are amplified by V2, the rf amplifier, and coupled to the control grid of V3A, the first mixer. Injection voltage is coupled to the cathode of V3A. Products of mixing are selected in the plate circuit of V3A tuned from 3.155 to 2.955 mc which is the bandpass intermediate frequency. Signals are coupled to the control grid of second mixer V4A with vfo injection voltage applied to the cathode of this tube. Oscillator Circuits CRYSTAL OSCILLATORS High-frequency crystal oscillator V3B provides injection voltage for the first mixer. The crystal oscillator output frequency is always 3.155 mc higher than the lower edge of the selected band. On bands below 12.0 mc, the oscillator plate circuit is tuned to the crystal frequency. At 12.0 mc and higher, the plate circuit is tuned to the second harmonic. The secondary winding of T2 couples injection voltage to the first mixer cathode circuit and furnishes a dc return to ground for mixer tube V3A. Dummy load R41 simulates the load presented by a transmitter when connected for transceiver operation. Crystal-controlled bfo V8B and associated circuitry furnishes injection voltage for the product detector. Crystals Y15 and Y16 provide the proper bfo frequency relationships to the mechanical filter passband to yield optimum audio response from the product detector. Crystal Y15 (453.650 kc) is used for lower sideband reception, and Y16 (456.35 kc) is used for upper sideband. This is due to sideband inversion in the first mixer. Capacitor C95 and coil L12 form a broadly resonant circuit at 455 kc. Oscillator voltage is developed across R49 and coupled by C100 to the cathode of V8A, the product detector tube. The crystal calibrator circuit provides marker signals at multiples of 100 kc. Variable capacitor C61 provides for adjustment to zero beat with WWV. The output of this oscillator is coupled to the receiver antenna circuits. Diode CR8 assists in the generation of the higher frequency harmonics. VARIABLE OSCILLATORS The vfo uses fixed capacitance and variable inductance to produce the required tuning range of 2.50135 to 2.70135 mc for LSB reception and 2.49865 to 2.69865 mc for USB, AM, and CW reception. Capacitor C303, in the frequency-determining network, is paralleled by variable capacitor C308 in series with diode CR301. This diode switches C308 in or out of the circuit depending on the polarity of the bias voltage impressed across its junction. With the MODE switch in the LSB position, diode CR301 is reverse biased and switches capacitor C308 out of the frequency-determining network. This condition will result in the tunable 2.50135 to 2.70135 mc signal desired. With the MODE switch in the USB, AM, or CW position, diode CR301 is forward biased and switches C308 into the frequency-determining network lowering the output frequency to the tunable 2.49865 to 2.69865 mc signal desired. Note that when C308 is properly adjusted, it shifts the vfo frequency by an amount equal to the frequency separation of crystals Y15 and Y16. This allows either sideband to be selected without retuning or recalibrating the dial. The vfo output voltage is coupled to the cathode of second mixer tube V4A and to the control grid of cathode follower V4B. The cathode follower prevents loading of the vfo circuits by cable capacity when operated in transceiver service. Tube V11 and associated circuitry comprise a 452.35 to 458.35 kc tunable bfo. The bfo tuning control is potentiometer R81. This control varies a positive dc voltage applied to the junction of voltage-variable capacitor CR4. The junction capacity of this device is proportional to applied voltage. Adjustment of R81 therefore varies the output frequency of the bfo. Voltage for the tuning circuit is stabilized by a regulator consisting of zener diode CR5 and resistor R82. Switch S13 completes the cathode circuit of either V8B or V11 thus turning on the desired bfo and turning off the other. The output circuits of both oscillators are coupled to the product detector. IF and Detector Circuits Output from the second mixer is connected to T4 and then to one of three mechanical filters FL1, FL2, or FL3 (FL2 and FL3 are not supplied) or to the tuned circuit of transformer T5. Mechanical filter FL1 (centered on 455 kc with a nominal bandpass of 2.1 kc) is selected for SSB reception, while FL2 and FL3 are optional filters to be used for CW operation. For AM operation, 455-kc transformer T5 is used to provide an increased bandwidth of approximately 5 kc. Output from these circuits is amplified by the if. preamplifier, V5A. Transformer T9 matches the preamplifier to the Q-multiplier, V5B. Control R57, the IF GAIN ADJUST, sets the receiver gain for the proper agc threshold sensitivity. The S-meter circuit is connected from the screen circuits of V6 and V7, the two if. amplifiers, to the cathode of V7. Under no-signal conditions, the voltage developed across R13 is equal to that developed across R21, and the meter reads zero. Application of agc causes the cathode current of V7 and the combined screen current of V6 and V7 to decrease. The voltage across R13 increases, the voltage across R21 decreases, and the meter reads up-scale by an amount which is proportional to signal strength. Output voltage from the second if. amplifier is coupled to the product detector, V8A. It is also coupled to separate AM and agc diode detectors. Bfo injection voltage is applied to the cathode of the product detector. Q-Multiplier and Notch Filter The notch filter is composed of coil L8 and associated capacitors and resistors. The rejection notch occurs at the resonant frequency of this circuit and is centered at 455 kc. Capacitor C132 is mechanically coupled to the REJECTION TUNING control which allows the notch frequency to be moved across the receiver if. passband. Potentiometer R77 is adjusted to provide optimum Q and depth of notch. Switch S10 shorts the filter circuit in the OFF position. The Q- multiplier is a feedback circuit which includes L8. This circuit multiplies the Q of L8 approximately ten times, thereby obtaining a much deeper and narrower rejection notch than would be provided by the filter alone. AGC and Control Circuits Signal voltage is coupled from the secondary of transformer T6 to one of the diode plates in V9 and rectified. This rectified signal voltage then passes through filter network R50 and C49 to the agc network consisting of resistors R24 and R88, and capacitors C50, C137, and C153. The agc network develops the desired agc signal and then applies it to the rf and if. amplifier stages. The parallel combination of R88 and C153 present the fast charge-discharge rate desired for elimination of small time duration interference; the parallel combination of R24 and C50 present a longer RC time constant allowing for a smoothly developed agc signal. Generation of agc voltage is delayed until the signal voltage at the diode plate exceeds the cathode bias on V9. Potentiometer R57 in the secondary of T9 is normally adjusted so that agc action is initiated with a receiver input signal of approximately 2 microvolts. This point is referred to as agc threshold. Manual control of rf gain is also accomplished through the agc line. A voltage divider circuit consisting of resistors R33, R55, and RF GAIN control R56 is connected across the negative 65-volt bias line. At the maximum gain setting, this circuit places a one-volt static bias on the agc line to furnish proper operating bias for rf amplifier V2. At lower control settings, increased bias is provided which reduces the gain. The dc grid return for the first mixer stage and MUTE jack J11 are connected to the junction of resistors R33 and R58. When the receiver function switch is placed in the STBY position, aground at J11 causes the receiver to operate in a normal manner. Removal of this ground causes cutoff bias to be applied to the mixer grid and increases bias on the agc line, thus muting the receiver. Audio Circuits Audio voltage from the appropriate detector is selected by S8A on the MODE switch and is coupled to the AF GAIN control. The CW SIDETONE jack, J10, is also connected to this point. A sidetone audio voltage of approximately 0.2 volt will produce a comfortable listening level at average gain settings. Audio is amplified in a 2-stage amplifier consisting of tubes V8 and V10. Capacitor C106 limits the audio response to 3 kc for AM and SSB reception, and capacitor C164 reduces it to 1.5 kc for CW reception. Three audio outputs are provided. Jack J8 is a4-ohm outlet for a speaker. The headphone jack is connected to a resistive divider across the 500-ohm tap on the output transformer. The divider provides a load for V10 when the impedance of headphones used is relatively high. The ANTI-VOX jack, J12, is also connected to the 500-ohm tap. At normal audio gain settings, 5 to 15 volts of audio are available at J12 for use with the anti-vox circuits in an associated transmitter. Power Supply Circuits The internal power supply furnishes filament, plate, and bias voltages for the receiver. Three high voltage values are developed consisting of a 190-volt dc unregulated voltage at the positive side of C59B, a 140-volt dc regulated voltage at the cathode of zener diode CR6, and a 135 volt dc unregulated voltage at the positive side of C59A. The high voltage winding of transformer T8; diode CR1, CR2, and CR6; resistor R86; and the filter network consisting of capacitors C59A, C59B, and C59C, resistor R51, and choke L6 make up the full-wave rectifier system which generates the three high voltage values mentioned above. Bias voltage is obtained by rectifying ac voltage from a voltage divider connected between one leg of the high voltage secondary and ground. The tube heaters and pilot lamps are connected to allow operation from a 6, 12, or 24-volt source. Heater, plate, and bias voltages may be furnished by an external source such as a mobile power supply. _________________________________________________________________ 32S-3/3A TRANSMITTER _________________________________________________________________ [IMAGE] THE COLLINS 32S-3/3A TRANSMITTER The Collins highly flexible 32S-3 Transmitter covers all the amateur bands between 3.4 mc and 30 mc with a power input of 175 watts PEP on SSB or 160 watts on CW. It has a nominal output of 100 watts. All of the dials and controls are clearly marked and human- engineered for operational efficiency. In the 32S-3, Collins design engineers have produced a transmitter with a minimum number of controls to offer you precise tuning. The 32S-3 can also be adapted for RTTY operation because of the high degree of stability of the unit. Grid block keying in CW with adjustment of characteristic from "soft" to "hard" for individual operator is provided. A combination of features found in no other transmitter on the amateur market gives you that top performance which you expect - and get - only in Collins transmitters. These features include: DUAL CONVERSION with the high frequency oscillator crystal- controlled, and low frequency oscillator variable, resulting in a frequency stability for Collins transmitters which has become the standard of the amateur field. COLLINS AUTOMATIC LOAD CONTROL which aids in preventing over modulation and provides up to 10 db compression for higher average talk power. COLLINS RF INVERSE FEEDBACK for improved linearity and reduction of distortion products and splattering. CW SPOTTING CONTROL which allows the 32S-3 frequency to be quickly and easily adjusted to zero beat with a signal tuned on the receiver. The carrier is momentarily keyed in the low level stages without disabling the receiver. A level control facilitates zero adjustment. COLLINS MECHANICAL FILTER providing a clean, clear signal without need for adjustment, additional audio filters, or special microphones. The 32S-3 comes equipped with the crystal sockets, crystals and bandswitch positions for eleven 200 kc bands. Crystal sockets and bandswitch position also are provided for two additional 200 kc bands between 28 mc and 30 mc. A fourteenth position, corresponding to the WWV position on the receiver, can be used for an additional 200 kc band in the 9.5-15.0 mc range, if desired. Regulation of oscillator voltages insures high frequency stability. The 32S-3 can be operated on any frequency in the range of 3.4-30 mc, except 5.0-6.5 mc, by installing an appropriate crystal. Plug-in crystals are available to convert any of the above amateur band channels to out-of-band channels. Easy access is provided to crystal oscillator patch cables from top of cabinet. Front panel selection of receiver VFO or transmitter VFO provides optional transceiver operation at the flick of a switch. While the 32S-3 provides ample RF power for excellent communication, it can be used without modification to excite the Collins 30L-1 or 30S-1 Linear Amplifier. _________________________________________________________________ 32S-3/3A SPECIFICATIONS FREQUENCY RANGE: 3.4-5.0 and 6.5-30.0 mc; bands are as follows: 80 meters - 3.4-3.6 mc, 3.6-3.8 mc and 3.8-4.0 mc. 40 meters - 7.0-7.2 mc and 7.2-7.4 mc. 20 meters - 14.0-14.2 mc and 14.2-14.4 mc. 15 meters - 21.0-21.2 mc, 21.2-21.4 mc and 21.4-21.6 mc. 10 meters - 28.5-28.7 mc. MODE: SSB (either sideband selectable) or CW. TYPE OF SERVICE: SSB continuous; CW 50% duty cycle. POWER REQUIREMENTS: 115 v, 50-60 cps. Power can be delivered by an external supply which must furnish 800 v dc at 220 ma for PA plates, 275 v dc at 175 ma, for PA screens and low voltage plates. Bias voltage adjustable between -60 v and -80 v dc; 6.3 v ac at 7.7 amps or 6.0 v dc at 6.0 amps or 12.0-14.0 v dc at 3.0 amps or 24.0-28.0 v dc at 1.5 amps. CW, key closed, 320 watts ac or 25 amps at 12 v. SSB, no modulation, 230 watts ac, 15 amps at 12 v. SSB, speech modulated, 255 watts ac, 20 amps at 12 v. PLATE POWER INPUT: 175 watts PEP on SSB; 160 watts on CW. POWER OUTPUT: 100 watts PEP (nominal) into 50 ohms. HARMONIC AND OTHER SPURIOUS RADIATION: Carrier suppression -50 db; unwanted sideband --50 db; oscillator feed-through and/or mixer products -50 db. Second harmonic -40 db. Third order distortion -30 db. NOISE LEVEL: 40 db below one tone carrier. AMBIENT TEMPERATURE: 0 -50 C. AMBIENT HUMIDITY RANGE: 0%-90%. ALTITUDE: 0-10,000 ft. PROTECTIVE DEVICES: Primary fuses provided in the power supply to be used with the equipment. SIZE: Transmitter with feet - 14-3/4" W, 7-3/4" H, 12-1/2" D. WEIGHT: 16 Lbs. FREQUENCY STABILITY: Within 100 cps after warm-up. CALIBRATION ACCURACY: 1 kc. BACKLASH: Not more than 50 cps. VISUAL DIAL ACCURACY: 200 cps on all bands. OUTPUT IMPEDANCE: Variable, 50 ohms nominal, capable of matching 2:1 SWR. CW SIDETONE: Provision for monitoring keying in receiver. Sidetone level is adjustable. KEYING CHARACTERISTICS: Keying is free of chirp and clicks. Modified break-in CW provided. Keyed carrier used for CW keying. Envelope rise and decay time adjustable. AUDIO INPUT: High impedance microphone or phone patch. AUDIO FREQUENCY RESPONSE: 300-2400 cps +6 db. AUDIO COMPRESSION CHARACTERISTICS: ALC operates on IF and RF amplifiers and is capable of 10 db compression. RF FEEDBACK: Approximately 10 db of RF feedback around PA and driver for improved PA linearity. _________________________________________________________________ Under the hood... [IMAGE] 32S-3/3A CIRCUITRY Type 32S-3A is a 175-watt input transmitter covering 3.4 to 30 MHz. The transmitter uses filter type sideband generation and heterodyne exciter principles. A crystal-controlled bfo, crystal-controlled high-frequency oscillator, and highly stable vfo form a double conversion circuit. The low- frequency if is 455 kHz, and the high-frequency if is 3.055 MHz with a 200-kHz wide passband, from 2.955 to 3.155 MHz. The 32S-3A may be connected in transceiver service with 75S- ( ) receivers. AF CIRCUITS Microphone or phone patch audio is coupled in the grid of first audio amplifier V1A, amplified, and coupled to the grid of second audio amplifier V1B. Output from V1B is coupled to the grid of cathode follower V2A across MIC GAIN control. Output from the cathode follower is fed to the balanced modulator. In TUNE, LOCK KEY, and CW positions of the EMISSION switch, output from the tone oscillator, V11B, is fed to the grid of the second audio amplifier. Tone- oscillator signal is taken from the plate of V1B to the grid of the VOX amplifier and the CW sidetone jack, J19. BALANCED MODULATOR AND ASSOCIATED CIRCUITS Audio output from the cathode of V2A is fed to the junction of CR3 and CR4. In USB and LSB positions of the EMISSION switch, the bfo voltage is fed to the junction of C187A and C187B. (In TUNE, LOCK KEY, and CW positions of the EMISSION switch, the bfo voltage by-passes the balanced modulator, if amplifier, and mechanical filter and is fed directly to one of the first mixer cathodes.) Output from the balanced modulator consists of both upper and lower sidebands and is coupled through if transformer T2 to the grid of if amplifier V3. Output from if amplifier V3 is fed to mechanical filter FL1. The passband of FL1 is centered at 455 kHz. This passes either upper or lower sideband depending upon the sideband polarity selected when the EMISSION switch connects bfo crystal Y12 or Y13. BALANCED MIXERS The 455-kHz single-sideband signal is fed to the first balanced mixer grids in push-pull; the plates are connected in push-pull; and the vfo signal is fed to the grids in parallel. The mixer suppresses the vfo signal and translates the 455-kHz single-sideband signal to a frequency between 2.955 and 2.155 MHz. This is the bandpass if. The coupling network between the plates of the first mixer and the grid of the second balanced mixer is broadbanded to provide a uniform response to the bandpass if. The bandpass if signal is fed to one of the grids of the second balanced mixer, and the high-frequency injection signal from the crystal oscillator V12 is fed to the signal input cathode and to the other grid. This arrangement suppresses the high-frequency injection signal within the mixer and translates the bandpass if signal to the desired operating band. RF CIRCUITS The slug-tuned circuits coupling V5 to V6, V6 to V7, and V7 to the power amplifier are ganged to the EXCITER TUNING control. The signal is amplified by rf amplifier V6 and driver V7 to drive power amplifier V8 and V9. Output from the power amplifier is coupled by a pi-network to the antenna through contacts of transmit-receive relay K2. Negative rf feedback from the pa plate circuit to the driver cathode circuit permits a high degree of linearity at the high power level of the pa tubes. Both the driver and pa stages are neutralized to ensure their stability. CONTROL CIRCUITS ALC Circuit Detected audio-frequency voltage from the power amplifier grid circuit is rectified by CR5 and CR6, and the negative dc output is fed to the ALC bus. A fast attack, slow release, dual time constant is used to prevent over-driving on initial syllables and to hold gain constant between words. The fast time constant ALC is applied to V6, and the slow time constant ALC is applied to V3. If the companion 30S-1 or 30L-1 Power Amplifier is used with the 32S-3A ALC, output from the 30S-1 or 30L-1 is fed back to the ALC bus. VOX and Anti-VOX Circuits Output from second audio amplifier V1B is fed to the grid of VOX amplifier V14A through VOX GAIN control R74. This audio input is amplified by V14A and rectified by VOX rectifier V10B. When the positive output of V10B is high enough to overcome the negative bias on V11A grid, the VOX relay is actuated to turn the transmitter on. Receiver output is fed from J13 through ANTI VOX GAIN control R85 to the grid of anti-VOX amplifier V14V. Output from V14B is rectified by anti-VOX rectifier V10A to provide the negative bias necessary to keep the transmitter disabled during receive periods. The anti-VOX circuit provides a threshold voltage to prevent loudspeaker output (picked up by the microphone) from tripping the VOX circuit into transmit. ANTI VOX GAIN control R85 adjusts the value of the anti-VOX threshold so that loudspeaker output will not produce enough positive dc output from the VoX rectifier to exceed the negative dc output from the anti-VOX rectifier and cause V11A to actuate VOX relay K1. Speech energy into the microphone will cause the positive VOX voltage to overcome the negative anti-VOX voltage and produce the desired action of K1. Contacts of relay K1 control relay K2, key line, PA and driver screens, receiver muting circuits, and oscillator plate voltages. Manual Gain Control The MIC GAIN control is a dual potentiometer. Section R8A controls microphone gain during SSB operation. Section R8B is a cathode potentiometer which controls the gain of rf amplifier V6 during CW, TUNE, or LOCK-KEY operation. This control will be set more clockwise in these modes than it will be in the USB or LSB modes. Oscillators Tone Oscillator The tone oscillator is used for VOX circuit actuation and sidetone generation during CW operation. It consists of an RC phase-shift oscillator operating at approximately 750 Hz. Its output is amplified by the second audio amplifier which then supplies the sidetone output and also activates the VOX circuitry to provide CW break-in. In TUNE and LOCK KEY, the oscillator is used in conjunction with the second audio amplifier to give sidetone output. The oscillator is turned on when EMISSION switch section S8C is in TUNE, LOCK KEY, or CW position. Beat-Frequency Oscillator The bfo is crystal controlled at either 453.650 kHz or 456.350 kHz depending upon whether Y12 or Y13 is selected by EMISSION switch section S8F. These crystal frequencies are on either side of the passband of mechanical filter FL1, so the carrier frequency is placed approximately 20 dB down on the skirts of the filter response. This carrier suppression is in addition to the 30-dB minimum suppression provided by the balanced modulator. Variable Frequency Oscillator The vfo uses fixed capacitors, a permeability tuned variable inductor, and fixed inductors to provide the tuning range of 2.5 to 2.7 MHz. The frequency-determining network is composed of capacitors C301, C302, C303, and C305, and inductors L301, L302, and L303. Capacitor C303 is paralleled by trimmer capacitor C308 and diode CR301 connected in series. A dc bias voltage is applied to the diode through rf isolation resistor R303. When LSB emission is selected, negative bias is applied to CR301 which switches C308 out of the circuit. Selection USB emission applies positive bias to CR301, causing it to conduct which switches C308 into the circuit. Proper adjustment of C308 shifts the vfo output frequency by an amount equal to the frequency separation of the two bfo crystals. This allows selection of either sideband without changing the suppressed carrier frequency of the exciter rf output. High-Frequency Crystal Oscillator High-frequency crystal oscillator V12 is crystal controlled by one of 14 crystals (11 supplied and 3 optional) selected by BAND switch S14, or by one of 14 crystals (none supplied) selected by BAND switch S11. Output from the high-frequency crystal oscillator is fed to the second mixer. This frequency is always 3.155 MHz higher than the lower edge of the desired transmit band. This high-frequency injection signal is the crystal fundamental frequency for all desired output signals below 12 MHz, but for operating frequencies higher than 12 MHz, the crystal frequency is doubled in the plate circuit of the oscillator. KEYING CIRCUITS Grid-block type keying is used for CW operation in the 32S- 3A. With the key up, a negative voltage is applied to the grids of a second audio amplifier and the second mixer. This prevents the amplified tone oscillator output from actuating the VOX circuitry and also cuts off the second mixer. The keying time constant of the second audio amplifier is fast attack and slow release with R127 and C115 determining the fast attack and R125 and C115 determining the slow release. The keying time constant of the second mixer is slow attack and slow release with the slow attack determined by R123, R124, and C81. R123, R124, C81, and C115 determine slow- release time. When keying takes place, second audio amplifier and the VOX circuitry are actuated before the second mixer. The release times of the second audio amplifier and second mixer are approximately the same. The VOX TIME CONSTANT control adjusts release time of the VOX circuitry to permit fast ON-OFF keying. Variable resistor R123 provides a choice between the extremes of "hard" and "soft" keying. This control and its effect are described fully in paragraph 2.1.3. Capacitor C115 determines, to a large extent, the release time of the "break." An additional effect is that the larger this capacitor, the greater is the "lag" introduced which is characterized by the bell-like type of keying well known to CW operators. The values of C115 and R123 have been chosen to produce generally acceptable keying. While it is not suggested the value of C115 should be changed, if the operator desires an increased amount of the bell-like characteristic, a slightly larger value will produce the effect. The additional "lag". however, will reduce the maximum speed at which the 32S-3A may be satisfactorily keyed. An additional amplifier following an exciter can change keying characteristics. A well-designed and adjusted linear amplifier, such as the 30L-1 or 30S-1, has a negligible effect on keying. A class C amplifier and its associated power supply, however, will generally have considerable effect, because cutoff bias must be overcome before the signal is amplified, thus causing a sharp wavefront. Proper adjustment of the keying waveshape can only be made with the exciter driving the class C amplifier. _________________________________________________________________ 62S-1 TRANSVERTER _________________________________________________________________ [IMAGE] THE COLLINS 62S-1 TRANSVERTER The Collins 62S-1 permits you to enjoy operation on either 6 or 2 meters by simply snapping a switch. No cable patching is required when changing from the HF to VHF frequencies. The self-contained unit, using the exciter's high voltage, supplies a 3-5 db receiver noise figure and transmitter input of 160 watts PEP. It can be used in any operational mode, as determined by the companion receiver and transmitter. Reflecting Collins emphasis on system engineering and flexibility in amateur equipment, the 62S-I is designed for use with the S/Line, KWM-2 and KWM-1; however, it will convert signals from most amateur equipment operating in the 14.0-14.2 mc range. The Collins 62S-1 assures you of outstanding performance with the following features: EXCELLENT FREQUENCY STABILITY with carefully designed oscillator circuits using 0.005% crystals. LINEAR DIAL CALIBRATION provides equivalent of 21 feet of bandspread on both 6 and 2 meters. SPURIOUS RADIATION meets FCC, Part 15, Sub Part C, regulations covering all very high frequency receiving equipment. Low CROSS MODULATION resulting in excellent rejection of strong adjacent signals is provided by three tuned circuits in the first RF stage. These circuits are retuned every 200 kc. EASE OF OPERATION is assured when used in conjunction with the Collins S/Line on all amateur bands between 80 and 2 meters with no connecting or disconnecting of enables. CHOICE OF MODES includes SSB, CW or AM, as determined by associated transmitter and receiver. The 62S-1 offers complete coverage of 49.6-54.2 mc and 143.6-148.2 mc frequency ranges in 200 kc increments using an oscillator-amplifier injection system for frequency conversion with 23 crystals (MARS band crystals not furnished) which can be selected for heterodyning down to 14.0-14.2 mc on receive, and up from 14.0-14.2 mc on transmit. The 62S-1 Converter is finished in light gray enamel with the front panel chemically etched to simulate leather and is compatible in appearance and styling with other Collins S/Line units. _________________________________________________________________ 62S-1 SPECIFICATIONS FREQUENCY RANGE: 49.6-54.2 mc; with crystals furnished: 6 meters - 50-54 mc in 200 kc increments. 2 meters - 144-148 mc in 200 kc increments. MODE: SSB, CW, AM or RTTY on transmit and receive,determined by exciter and receiver. TYPE OF SERVICE: Attended operation. Continuous on receive and transmit. POWER REQUIREMENTS: 115 v ac, 50-60 cps at approximately 75 watts. Power can be delivered by an external power supply which must furnish 800 v dc at 220 ma for the PA plate circuit: 275 vdc at 20 ma for the PA screen circuit. PLATE POWER INPUT: 160 watts. POWER OUTPUT: 65 watts PEP minimum into a 50 ohm load. NOISE LEVEL: 40 db below rated PEP output. HARMONIC AND OTHER SPURIOUS RADIATION: Oscillators and mixer products at least 60 db below PEP. Second harmonic at least 35 db below PEP. AMBIENT TEMPERATURE RANGE: 0 -50 C. AMBIENT HUMIDITY RANGE: 0%-90%. PROTECTIVE DEVICES: Primary fusing in power supply. SIZE: With feet - 14-3/4" W, 7-3/4" H, 13" D. WEIGHT: 25 Lbs. FREQUENCY STABILITY: 0.005% crystals are used throughout in the 62S-1. OUTPUT IMPEDANCE: Variable; 50 ohms nominal, capable of matching 2:1 SWR. SENSITIVITY: 2 meters - 1.2 uv maximum for 10 db S+N/N using 3 kc audio bandwidth (NF approximately 4); 6 meters - 1.3 uv maximum for 10 db S+N/N using 3 kc audio bandwidth (NF approximately 4). SPURIOUS RESPONSES: At least 50 db below a 1 uv desired signal level. Image rejection greater than 100 db on 6 meters. Greater than 60 db on 2 meters. _________________________________________________________________ Under the hood... [IMAGE] 62S-1 CIRCUITRY General The 62S-1 VHF Converter is a 6- and 2-meter transmitting and receiving converter covering the ranges of 49.6 to 54.2 mc and 143.6 to 148.2 mc in 200-kc increments. The associated h-f transmitter and receiver must cover the range of 14.0 to 14.2 mc. The transmitter portion of the 62S-1 consists of five stages: a mixer, V1, in which the h-f exciting signal is converted to the vhf operating frequency; three linear voltage amplifiers, V2, V3, and V4; and a linear power amplifier, V5, operating in class AB1. Plate voltage is removed from the mixer and the first voltage amplifier while receiving. The receiver portion consists of a triode r-f amplifier, V7, and a triode mixer, V8, to convert received vhf signals to the h-f receive frequency. Internal relays ground the r-f amplifier grid and remove plate voltage from both the r-f amplifier and the mixer while transmitting. Injection voltage for both the transmitter mixer and the receiver mixer is supplied by an oscillator-amplifier system, V6, V9, and V10. The crystal oscillator, V6, uses 23 crystals spaced 200 kc apart to provide a total range of 4.6 mc on either 6 or 2 meters. For 2-meter operation, a second crystal oscillator is switched into the circuit, and the 94- mc output from this oscillator is mixed with the output of the first crystal oscillator to provide the required injection frequencies. Transmitter Circuits The net inductance of L1 in series with L2 is parallel tuned to the 6-meter band by the combination of C1, C2, and circuit capacitance. Tuning within the band is done by varying the inductance of L2 which consists of a circular ring with a rotating wiper arm. When operating on 2 meters, C2 is switched out of the circuit, L3 is switched in parallel with L1, and L4 is switched in parallel with L2. This reduces the net inductance of the circuit and the inductance range of L2 to provide the proper LC ratio and tuning range for 2-meter operation. The PA plate circuits operate on the same principle with slight differences to accommodate PA operating parameters. The PA tank circuit is resonated on 2 meters by the output capacitance of V5, the PA tube. A trimmer to provide additional capacitance is switched into the circuit on 6 meters. Double contacts are used on the PA bandswitch wafer to reduce inductive effects and to handle the circulating r-f current. Link output coupling is used with a series variable capacitor for loading adjustments. The power amplifier stage uses a 7034/4X150A tube which has an external anode requiring forced-air cooling. With the air supply provided in the 62S-1, plate dissipation should be held to a maximum of 120 watts. The PA grid circuit includes an alc rectifier consisting of diodes CR1 and CR2 connected as a half-wave doubler. An external load resistance of approximately 2 megohms is required, and usually is part of the h-f exciter alc circuit. Receiver Circuits Triode tubes are used in the r-f amplifier and mixer stages to minimize noise. The type 6ER5 tube used in these stages employs a partial shield between grid and plate to reduce grid-to-plate capacitance, thereby easing neutralizing requirements. Neutralization is used only on 2 meters, and there the principal function is to obtain a lower noise figure. An r-f gain control is included in the r-f amplifier cathode circuit so that the gain can be reduced when extremely strong unwanted signals are present near the desired signal frequency. Four tuned circuits in the mixer plate circuit provide a uniform response across the i-f output range, but response outside the passband is rapidly attenuated to minimize spurious responses. The vhf tuned circuits and bandswitching in the receiver portion function in essentially the same way as those in the transmitter. An additional contact is used on bandswitch wafers in Z6 and Z7 to switch the neutralizing coil, L36, into the circuit on 2 meters. The variable inductor rings, illustrated by L2 in figure 3-2, are ganged to the main dial so that the 62S-1 receiver tuning tracks with the 200-kc band selected on the dial. This eliminates the need for broadband r-f circuits and provides a significant reduction in cross modulation over an equivalent broadband system. Frequency Conversion System An oscillator-amplifier system provides injection frequencies for frequency conversion. The system consists of the master oscillator subunit, a second stage which functions as an amplifier on 6 meters and as an oscillator- mixer on 2 meters, and a third stage which is an injection amplifier on both bands. The second and third stages are located in the receiver subunit The master oscillator, V6, is crystal controlled using 23 selectable crystals to provide output frequencies from 35.6 to 40.0 mc in 200-kc steps. This frequency range provides transmitter output in the 6-meter band when mixed additively with 14.0- to 14.2-mc output from the exciter. A difference mix in the receiver mixer, V8, converts received 6-meter signals to the h-f range. Tube V10 and the pentode section of V9 are used as buffer amplifiers. On 2 meters, the two sections of V9 function as a 94-mc crystal-controlled oscillator. The pentode section also serves as a mixer. Output frequencies from the master oscillator are mixed additively with 94 mc to produce injection frequencies ranging from 129.6 to 134.0 mc. These injection frequencies then are used to heterodyne the h-i excitation to 2-meter operating frequencies and to convert received 2-meter signals to the h-f range. Tuned circuits are used in the plate circuits of both crystal oscillators, V6 and V9, and the injection amplifier, V10. The plate circuit of V6 uses 23 selectable coils which are mounted on a turret. The appropriate coil is switched into the circuit in conjunction with the crystal selected. Both the turret and the crystal selector switch are controlled by the main selector. A double-tuned circuit, Z10, is switched into the pentode plate circuit of V9 on 2 meters to suppress unwanted mixing products. The inductor rings of Z10 are ganged to the main dial for in-band tuning. Switch sections S11, S12, and S13 are ganged to the bandswitch. A parallel-tuned trap, FL2, provides added attenuation to spurious products on 2 meters. The basic functions of the 62S-1 control circuits are to provide compatible operation with h-f exciter vox and control circuits and convenient switching from h-f to vhf. For vhf operation, the following switching is done by the 62S-1 function switch in VHF TUNE and VHF OPR positions: Screen voltage is switched from the exciter PA to the 62S-1 PA by S15B-front. Exciter vox control circuits, which must furnish a ground to transmit, are connected via the HF ANT. RELAY IN jack and S15B-rear to the coil of relay Kl which is connected in series with the coil of K3. Plate voltage is connected to the opposite coil terminal of K3 via S15A-rear. Keying the exciter then keys the 62S-1 also. The HF RF IN jack is connected to the 62S-1 receiver output circuit by S15A-front. Converted vhf signals are routed to the h-f receiver via this jack and the h-f antenna changeover relay (built into Collins exciters). The keying circuit to the HF ANT. RELAY OUT jack is disabled by S15B-rear so that the associated h-f linear amplifier, if used, is not keyed by the h-f exciter control circuits when operating vhf. _________________________________________________________________ KWM-2/2A TRANSCEIVER _________________________________________________________________ [IMAGE] THE COLLINS KWM-2/2A TRANSCEIVER Unmatched for versatility, dependability and mobility, the Collins KWM-2 maintains a reputation of outstanding performance in mobile and fixed station applications. The KWM-2 power input is 175 watts PEP on SSB or 160 watts on CW. It transmits on voice or CW with a nominal output of 100 watts for complete coverage on 80 through 10 meters. Crystals are provided for all HF bands except 10 meters where one crystal is supplied with provision for two additional crystals. The transceiver is finished in light gray enamel with a simulated leather front panel to match the S/Line. The first available amateur mobile SSB transceiver was in the Collins KWM series. The KWM-2 continues to lead the field with the following features: FILTER TYPE SSB GENERATION providing unsurpassed performance on both transmit and receive. AUTOMATIC LOAD CONTROL which keeps the signal level adjusted to its rated PEP, resulting in an increase in average talk power. INVERSE RF FEEDBACK which improves linearity and reduces distortion products, giving the cleanest signal on the air. PERMEABILITY-TUNED VARIABLE OSCILLATOR with linearity and stability providing the best frequency calibration available. ONE KC DIVISION on all bands, eliminating frequency searching and allowing you to meet anyone on sked, on any band 80 through 10 meters. Compactness and efficiency of the KWM-2 are achieved through Collins' advanced design of having all tuned circuits and several tubes function in the dual role of transmitting and receiving. The same oscillators, Mechanical Filter and RF amplifier serve both the transmitter and receiver. CW break- in and monitoring sidetone circuits are built in. Easily accessible controls on the front panel of the KWM-2 include the OFF-ON-NB-CAL SWITCH, EXCITER TUNING, ZERO SET, PA TUNING, LOADING, MIC GAIN, BAND SWITCH, AF GAIN, RF GAIN, EMISSION and METER SWITCH. The KWM-2A is an extended frequency version of the KWM-2 for MARS (Military Affiliate Radio Service) and military applications. The KWM-2A has an additional crystal board permitting the operator to add 14 crystals to cover frequencies outside the amateur bands. The KWM-2A has a front panel switch and indicator, allowing instant switching between the two crystal boards. _________________________________________________________________ KWM-2/A SPECIFICATIONS FREQUENCY RANGE: 3.4-5.0 and 6.5-30.0 mc; with crystals furnished, bands are as follows: 80 meters - 3.4-3.6 mc, 3.6-3.8 mc and 3.8-4.0 mc. 40 meters - 7.0-7.2 mc and 7.2-7.4 mc. 20 meters - 14.0-14.2 mc and 14.2-14.4 mc. WWV - 14.8-15.0 mc. 15 meters - 21.0-21.2 mc, 21.2-21.4 mc and 21.4-21.6 mc. 10 meters - 28.5-28.7 mc. MODE: SSB (either sideband selectable) or CW. TYPE OF SERVICE: SSB continuous; CW 50% duty cycle. POWER REQUIREMENTs: 115 v, 50-60 cps; power consumption approximately 235 watts in receive function and approximately 475 watts in transmit. In mobile operation, 800 v dc required at approximately 175 ma; 275 v dc at 190 ma; a bias supply adjustable between - 60 v and - 80 v; and 6 v, 12 v or 24 v dc at 11.0, 5.5 or 2.75 amps respectively. PLATE INPUT: 175 watts PEP on SSB; 160 watts on CW. POWER OUTPUT: 100 watts PEP (nominal) into 50 ohms. HARMONIC AND OTHER SPURIOUS RADIATION: Carrier suppression -50 db; unwanted sideband -50 db; oscillator feed-through and/or mixer products -50 db. Second harmonic -40 db. Third order distortion -30 db. NOISE LEVEL: 40 db below single tone carrier. AMBIENT TEMPERATURE RANGE: 0 -50 C. AMBIENT HUMIDITY RANGE: 0%-90%. ALTITUDE: 0-10,000 ft. SIZE: With feet - 14-3/4" W, 7-3/4" H, 14" D. WEIGHT: 18 Lbs. 3 oz. FREQUENCY STABILITY: Within 100 cps after warm-up. CALIBRATION ACCURACY: 1 kc. BACKLASH: Not more than 50 cps. VISUAL DIAL ACCURACY: 200 cps on all bands. OUTPUT IMPEDANCE: Variable, 50 ohms nominal, capable of matching 2:1 SWR. KEYING CHARACTERISTICS: Keying is free of chirps and clicks. Break-in CW and sidetone provided. AUDIO INPUT: High impedance microphone or phone patch. AUDIO FREQUENCY RESPONSE: 300-2400 cps + 6 db. AUDIO COMPRESSION CHARACTERISTICS: ALC operates on IF and RF amplifier stages and is capable of 10 db compression. RF FEEDBACK: Approximately 10 db of RF feedback around PA and driver for improved linearity. RECEIVER SENSITIVITY: 0.5 uv for 10 db signal-to-noise. RECEIVER SELECTIVITY: 2.1 kc bandwidth at 6 db down; 4.2 kc bandwidth at 60 db down. RECEIVER SPURIOUS RESPONSE: Image rejection better than 50 db. Internal spurious below 1 uv equivalent antenna input. RECEIVER OUTPUT LEVEL: 1.0 watt maximum. AUTOMATIC GAIN CONTROL: The audio output level does not change more than 20 db as the input signal is changed from 5 uv to 1 v. Fast attack and slow release provide excellent AVC action on voice and CW. VIBRATIONS: 2 g at 10-33 cps. _________________________________________________________________ Under the hood... [IMAGE] KWM-2/A CIRCUITRY The KWM-2/2A is an SSB or CW transceiver operating in the range between 3.4 and 30.0 mc. It consists of a double- conversion receiver and a double-conversion exciter- transmitter. The transmitter and receiver circuits use common oscillators, and a common mechanical filter, as well as a common r-f amplifier. The transmitter low-frequency i-f and the receiver low-frequency i-f is 455 kc. The high- frequency i-f for both is 2.955 to 3.155 mc. This is a band- pass i-f which accommodates the full 200-kc bandwidth. Transmitter Circuit A-F CIRCUITS Microphone or phone-patch input is connected to the grid of the first audio amplifier, V1A, amplified, and coupled to the grid of the second audio amplifier V11B. Output from V11B is coupled to the grid of cathode follower V3A through the MIC GAIN control, R8. Output from the cathode follower is fed to the resistive balance point of the balanced modulator. In TUNE, LOCK, and CW positions of the EMISSION switch, output from the tone oscillator, V2B, is fed to the grid of the second audio amplifier. The amplified tone oscillator signal is taken from the plate of V11B and coupled to the grid of the vox amplifier V14B to activate the vox circuits in CW operation. This signal is also fed to the grid of the first receiver a-f amplifier, V16A, for CW monitoring. BALANCED MODULATOR AND LOW-FREQUENCY I-F CIRCUITS Audio output from the cathode of V3A and the bfo voltage are fed to a diode quad balanced modulator (CR1, CR2, CR3, and CR4). Both upper and lower sideband outputs from the balanced modulator are coupled through i-f transformer T1 to the grid of the i-f amplifier, V4A. Output from the i-f amplifier is fed to the mechanical filter, FL1. The passband of FL1 is centered at 455 kc. This passes either upper or lower sideband, depending upon the sideband selected when the EMISSION switch connects bfo crystal Y16 or Y17. The single-sideband output of FL1 is connected to the grids of the first transmitter mixer in push-pull. BALANCED MIXERS The 455-kc single-sideband signal is fed to the first balanced mixer grids in push-pull. The plates of the mixer are connected in push-pull, and vfo signal is fed to the two grids in parallel. The mixer cancels the vfo signal energy and translates the 455-kc single-sideband signal from the balanced modulator to a 2.955- to 3.155-mc single-sideband signal. The T2-L4 combination between the first and second mixer provides broadband response to the 200-kc variable i-f output (2.955 to 3.155 mc) from the first transmit mixer V5. The band-pass i-f signal is fed to one of the grids of the second balanced mixer, and the high-frequency injection signal energy from crystal oscillator V13A is fed to the cathode and the other grid. This arrangement cancels the high-frequency injection signal energy within the mixer and translates the band-pass i-f signal to desired operating band. R-F AND ALC CIRCUITS The slug-tuned circuits coupling V6 to V7, V7 to V8, and V8 to the power amplifier are ganged to the EXCITER TUNING control. The signal is amplified by the r-f amplifier, V7, and the driver, V8, to drive the power amplifier, V9 and V10. Output from the parallel power amplifiers is tuned by a pi- network and fed to the antenna through contacts of transmit- receive relay K3. Negative r-f feedback from the PA plate circuit to the driver cathode circuit reduces distortion in the output signal. Both the driver and PA stages are neutralized to ensure stability. When r-f driving voltage to the PA becomes great enough that positive peaks drive the PA grids positive, the grids begin to draw current and the signal is detected. This produces an audio envelope. The audio is rectified by the alc rectifier, V17A, which is connected to produce a negative d-c voltage. The voltage is filtered by C159, C160, R118, and R119 (which also determine the alc time constants), and used to control the gain of V4A and V7. This system allows a high average level of modulation without driving the PA tubes well into the grid current region, which would result in increased distortion. Receiver Circuits R-F CIRCUITS Signal input from the antenna is connected through relay contacts to the tuned input circuit, T3. The signal is applied from T3 to the grid of the receiver-transmitter r-f amplifier, V7. Amplified signal from V7 is applied from the tuned circuit, consisting of L10 and band switch selected capacitors, to the grid of the receiver first mixer, V13B. RECEIVER MIXERS The input r-f signal is fed to the grid of V13B, and the high-frequency oscillator injection signal is fed to the cathode of V13B. The difference product of the first mixer is applied from the plate of the tube to variable i-f transformer T2. Output of T2 in the range of 2.955 to 3.155 megacycles is applied to the grid of the second receiver mixer, V17B, across parallel-tuned trap circuit Z5. This trap circuit minimizes a spurious response which would otherwise result from harmonics of the high-frequency crystal oscillator. When signal input is applied to the grid of V17B and vfo injection signal is applied to the cathode of V17B, the 455-kc difference product is fed from V17B plate to mechanical filter FL1. I-F CIRCUITS The output from FL1 is applied to the grid of the first i-f amplifier, V1B. The i-f signal is amplified by V1B and V3B and applied through T5 to avc rectifier V15A and to the grid of product detector V15B. Beat-frequency oscillator signal is applied to the cathode of V15B, and the product of mixing is the detected audio signal. Output of the avc rectifier circuit is applied to the two receiver i-f amplifiers and through contacts of relay K4 to the receiver-transmitter r-f amplifier. This avc voltage controls the gain of the receiver and prevents overloading. A-F CIRCUITS Output from the product detector is applied through the A.F. GAIN control, R92, to the grid of the first a-f amplifier, V16A. Amplified audio output of V16A is coupled to the grid of the a-f output amplifier, V16B, which produces the power to operate a speaker, headphones, or phone patch. Oscillators The transceiver contains the tone oscillator, the beat- frequency oscillator, the variable-frequency oscillator, the high-frequency crystal oscillator, and the crystal calibrator. TONE OSCILLATOR The tone oscillator operates when the EMISSION switch is in LOCK, TUNE, or CW position. It is a phase-shift oscillator operating at approximately 1500 cps. Its output is fed to the transmitter audio circuits for CW operation. Some of the output from the tone oscillator is applied to the receiver audio circuits for sidetone monitoring in CW operation. Due to the 1500-cps tone applied to the balanced modulator during CW operation, the actual transmitted CW signal will be 1500 cps above the KWM-2/2A dial reading. BEAT-FREQUENCY OSCILLATOR The bfo is crystal controlled at either 453.650 or 456.350 kilocycles, depending upon whether Y16 or Y17 is selected by EMISSION switch section S9H. The unused crystal is shorted out by this switch section. These crystal frequencies are matched to the passband of the mechanical filter, L1, so that the carrier frequency is placed approximately 20 db down on the skirts of the filter response. This 20-db carrier attenuation is in addition to the 30-db suppression provided by the balanced modulator. VARIABLE-FREQUENCY OSCILLATOR The vfo uses fixed capacitance and variable inductance to tune the range of 2 .5 to 2 .7 mc . The series combination of capacitor C308 and diode CR301 is connected in parallel with capacitor C303. The diode switches C308 into or out of the circuit, depending upon the polarity of a bias voltage impressed across the diode junction. When USB emission is selected, the bias is positive and C308 is switched into the circuit. The capacitor then is adjusted to shift the vfo frequency by an amount equal to the frequency separation of bfo crystals Y16 and Y17. This allows the selection of either sideband without upsetting tuning or dial calibration. HIGH-FREQUENCY CRYSTAL OSCILLATOR The high-frequency crystal oscillator, V13A, is crystal controlled by 1 of 14 crystals selected by BAND switch S2. Output from the high-frequency crystal oscillator is fed to the transmitter second mixer and to the crystal oscillator cathode follower. The cathode follower provides isolation and impedance match between the crystal oscillator and the receiver first mixer cathode. The output frequency of this oscillator is always 3.155 mc higher than the lower edge of the desired band. This high-frequency injection signal is the crystal fundamental frequency for all desired signals below 12 megacycles. For operating frequencies higher than 12 mc, the crystal frequency is doubled in the plate circuit of the oscillator. Instructions for calculating crystal frequencies for the desired bands are given in section 2. CRYSTAL CALIBRATOR The 100-kc crystal calibrator, V12A, is the pentode section of a type 6U8A tube. Its output is coupled to the antenna coil, T3 . The calibrator may be trimmed to zero beat with WWV by adjustment of capacitor C76. Vox and Anti-vox Circuits Audio output voltage from the second microphone amplifier, V11B, is coupled to the VOX-GAIN control R39. A portion of this voltage is amplified by vox amplifier V14B and fed to the vox rectifier, which is one of the diodes of V14. The positive d-c output of the vox rectifier is applied to the grid of vox relay amplifier V4B. causing it to conduct current and actuate the vox relay, K2. Contacts of K2 switch the receiver antenna lead, the other relay coils, and bias voltage . Relays K3 and K4 switch the metering circuits from receive to transmit, the low plate voltages from receive to transmit tubes, and the avc and alc leads. The anti-vox circuit provides a threshold voltage to prevent loudspeaker output (picked up by the microphone circuits) from tripping the KWM-2/2A into transmit function. Some of the receiver output audio voltage is connected through C235 to the ANTI-VOX GAIN control, R45. Signal from the slider of this potentiometer is rectified by the anti-vox rectifier, which is the other diode of V4. Negative d-c output voltage from the anti-vox rectifier, connected to the grid of V4B, provides the necessary anti-vox threshold. ANTI-VOX GAIN control R45 adjusts the value of the anti-vox voltage threshold so that loudspeaker output will not produce enough positive d-c output from the vox rectifier to exceed the negative d-c output from the anti-vox rectifier and cause V4B to actuate K2. However, speech energy into the microphone will cause the positive vox voltage to overcome the negative anti-vox voltage and produce the desired action of K2. _________________________________________________________________ 30L-1 LINEAR AMPLIFIER _________________________________________________________________ [IMAGE] THE COLLINS 30L-1 LINEAR AMPLIFIER The Collins 30L-1 Linear Amplifier has 1000 watts PEP power input on SSB and 1000 watts average on CW on all bands. It can be driven by the Collins 32S-3 Transmitter Collins KWM-2 or KWM-1 Transceiver, or most 70-100 watt exciters. Finished in the same attractive light gray as Collins' famous S/Line equipment and the KWM-2, the 30L-1 has all the controls conveniently accessible on the front panel. This linear amplifier is completely self-contained and designed for table-top use. It is easily transported in a CC-2 Carrying Case. The Collins 30L-1 features: AUTOMATIC LOAD CONTROL allowing a high average level of modulation and optimum power output from the amplifier, within the rated limits of distortion. RF INVERSE FEEDBACK reduces distortion products giving cleanest signal on the air. SOLID STATE RECTIFIERS resulting in heat reduction. SELF-CONTAINED POWER SUPPLY with safety interlock circuits for grounding the high voltage when the cover is removed. AUTOMATIC ANTENNA TRANSFER ON THE ON-OFF SWITCH permits the 30L-I to be switched in or out of the circuit at will by operating the switch. The 30-L-1 provides SSB and CW emission and covers the 80, 40, 20, 15 and 10 meter bands. Provisions are made for general coverage use, too. Automatic Load Control voltage from the 30L-1 is fed back to the exciter, providing maximum talking power without over driving and distortion. In combination with RF inverse feedback, Collins' exclusive Automatic Load Control provides not only more power, but a sharper signal than any comparable unit in the amateur field. The 30L-1 is a grounded grid linear amplifier with four 811 A Triodes. They can be replaced without removing the unit from the cabinet. The 811A's are instantly heated; thus, there is no delay in warm-up. Indicating devices on the 30L-1 include a panel meter monitoring final amplifier plate current, plate voltage, and tuning circuit. With the meter switch in tune position, the 30L-1 uses an exclusive comparator circuit which can be operated by simply adjusting tuning and loading controls to zero the meter. The 30L-1's RF and power supply compartment covers operate safety interlock switches for protection of the operator. Cover removal closes these switches and shorts the high voltage to ground. This arrangement protects the operator from accidentally coming in contact with high voltage dc, which is present in either compartment. The unit can be operated outside amateur band limits; however, retuning the input circuits may be necessary. Such retuning presents the proper load impedance to the exciter. _________________________________________________________________ 30L-1 SPECIFICATIONS FREQUENCY RANGE: 3.4 - 30.0 mc, covering 80, 40, 20, 15 and 10 meter amateur bands. BY retuning input circuit as necessary, the following general coverage bands can he accommodated: FREQUENCY BAND TOTAL COVERAGE 3.5 mc 3.4- 5.0 mc 7.0 mc 6.5- 9.5 mc 14.0 mc 9.5-16.0 mc 21.0 mc 16.0-22.0 mc 28.0 mc 22.0-30.0 mc MODE: SSB or CW. TYPE OF SERVICE: Attended operation SSB continuous; CW 50% duty cycle. POWER REQUIREMENTS: 115 v or 230 v, 50-60 cps; CW,key closed, 1200 watts ac; SSB, no modulation, 300 watts ac; SSB, speech modulated, 550 watts ac. DRIVE POWER: 70 - 100 watts for full output. PLATE POWER INPUT: 1000) watts PEP on SSB; 1000 watts on CW on all bands. POWER OUTPUT: 500 watts PEP into 50 ohms on all bands. HARMONIC AND OTHER SPURIOUS RADIATION: Second harmonic -40 db; third order distortion -30 db at full output. NOISE LEVEL: 40 db below one tone carrier. AMBIENT TEMPERATURE: 0 - 50 C. AMBIENT HUMIDITY RANGE: 0% - 90%. ALTITUDE: 0-10,000 ft. PROTECTIVE DEVICES: All removable panels interlocked. Input line fused - 8 amps on each side. SIZE: With feet - 14-3/4" W, 7-3/4" H, 13-3/4" D. WEIGHT: 38 Lbs. (17.24 kg) . OUTPUT IMPEDANCE: Variable. Nominally 50 ohms unbalanced with not more than 2:1 SWR on the amateur hands. AUDIO COMPRESSION CHARACTERISTICS: ALC operates from the amplifier RF plate voltage. Threshold is adjustable and factory preset. _________________________________________________________________ Under the hood... [IMAGE] 30L-1 CIRCUITRY GENERAL The 30L-1 is a portable r-f linear power amplifier, including plate power and bias supplies. It is capable of 1000 watts PEP input power in SSB or 1000 watts d-c input in CW service with any exciter (such as the KWM-1, KWM-2/2A, or 32S-1) capable of 70 watts PEP output. It covers the amateur bands between 3.5 and 29.7 mc. In addition, the amplifier may be operated outside the amateur bands over certain ranges of frequency. These ranges are specified in above. The power amplifier stage uses four 811A triodes connected in parallel with cathode drive. INPUT CIRCUITS Broadband pi-network circuits couple the exciting signal into the cathode circuits of the power amplifier tubes. In conjunction with the interconnecting r-f feed cable supplied, this presents a nearly constant 50-ohm load to the exciter This aids in maintaining the low level of distortion products under modulation. For this reason, it is important not to alter the length of interconnecting cable supplied with the amplifier. OUTPUT CIRCUITS The plate circuit of the power amplifier is tuned by a pi network consisting of C32, L9, L10, and C33. Capacitor C32 resonates the tank circuit at the frequency in use. It is adjusted by the TUNING control on the front panel. The four-gang capacitor, C33, is adjusted by the LOADING control to match the pi-network circuit to the impedance presented by the antenna and feed system in use. Output from the plate tank circuit is connected through the contacts of antenna changeover relay, K1, to the antenna when the control circuits are energized. POWER SUPPLY CIRCUITS Two dc power supplies and one a-c filament supply are included in the 30L-1. The amplifier may be connected to a 115-volt single-phase or to a 230-volt, three-wire, single- phase source. Where practical, the 230-volt, three-wire connection is recommended. Power transformer T1 has two primary windings. These windings are connected in parallel for 115-volt operation, and in series for 230-volt operation. The 6.3-volt secondary winding provides filament power for the 811A tubes through r-f choke L8. It also powers the pilot lamp in the meter. Another secondary winding applies voltage through surge resistor R9 to semiconductor rectifier CR20. This is a half-wave circuit connected to furnish blocking bias to the amplifier tubes under receive conditions and operating bias when transmitting. It also furnishes power for changeover relay K1. Voltage from the third secondary winding is applied to two semiconductor rectifier strings connected in full-wave voltage doubler configuration. These strings consist of CR1-CR8, C44-C51 in one string, and CR9-CR16, C52-C59 in the other. The parallel capacitors equalize the reverse voltages impressed across the diode junctions and protect against damage by transients. The output of this supply provides approximately 1600 volts dc under load for the amplifier tube plates. SAFETY INTERLOCK CIRCUITS The rf and power supply compartment covers operate safety interlock switches for operator protection. Switch S5 is located in the power supply compartment. Switches S6 and S7 are located in the rf compartment. Cover removal closes these switches and shorts the high voltage to ground. This arrangement protects the operator from accidentally coming in contact with high-voltage d-c which is present in either compartment. POWER CONTROL CIRCUITS The front-panel ON-OFF switch breaks one side of the a-c line in the OFF position. When operated to the ON position, a-c power is applied to the power transformer primaries and the tube-cooling fan B1. Overload protection is provided by eight-ampere fuses F1 and F2. These are used for both 115-volt a-c and 230-volt a-c operation. ALC CIRCUITS Automatic load control (alc) is a compressor circuit operating at radio frequencies. In the 30L-1, the grid-to- plate capacities of the amplifier tubes in conjunction with capacitors C22, C23, C24, and C25 form capacitive voltage dividers. Under modulation, an rf voltage is developed across these dividers and L3. It is coupled to the alc rectifier CR19 through capacitor C72. The r-f voltage is rectified and filtered to produce a negative d-c control voltage which is proportional to the modulation level. The load resistor for CR19 must be provided by the exciter alc circuits. This voltage is applied to the control grid of a low-level r-f amplifier tube or tubes in the exciter. The time constants of these circuits have fast attack, slow- release characteristic. The alc threshold is controlled by the amount of reverse bias on CR19. This voltage is developed across R7 in the plate supply bleeder network, and varied by potentiometer R16. It is adjusted at the factory for optimum operation in conjunction with the internal alc circuits of exciters such as the KWM-1, KWM-2/2A, or 32S-1. Normally it will not need readjustment. This system allows a high average level of modulation and optimum power output from the amplifier, within the rated limits of distortion. METERING CIRCUITS One section of the METER switch, S3, selects the output voltage from a tuning and loading bridge circuit. This circuit consists of the power amplifier tubes, CR17, CR18, and the associated load resistors and filter networks. The bridge is balanced when the plate circuit TUNING and LOADING controls are adjusted to present the proper load impedance to the power amplifier plates. The meter then will read zero. The second section of the meter switch connects the meter to the plate supply through a four-megohm multiplier resistor to indicate the dc voltage output. It is read on the D.C. KILOVOLT scale. The third section of the meter switch connects the meter, through R10, across shunt, R8. This indicates power amplifier plate current. It is read on the D.C. AMPS scale. _________________________________________________________________ 30S-1 LINEAR AMPLIFIER _________________________________________________________________ [IMAGE] THE COLLINS 30S-1 LINEAR AMPLIFIER Add the Collins 30S-1 Linear Amplifier to your station and you will have the cleanest, loudest signal on the air. The Collins 30S-1 Linear Amplifier features: RF INVERSE FEEDBACK for better linearity. INSTANT SWITCHING between low and full kilowatt power. QUICK AND ACCURATE TUNING, offering the amateur a bonus in ease of operation and optimum operating efficiency. AUTOMATIC LOAD CONTROL, assuring a clean signal. COOLING SYSTEM which operates quietly and efficiently. SIMPLE AND DIRECT CONNECTION between the 30S-1 and the exciter and station control unit. PROTECTIVE CIRCUITRY which protects tubes and other components from damage due to mistuning or malfunction. Requiring 70-100 watts driving power (supplied by the Collins 32S-3 Transmitter or KWM-2 Transceiver) the 30S-1 Linear Amplifier provides your SSB and CW station with the full legal power input for SSB (1 kw average) or 1 kw input for CW transmission. All the 30S-1 controls are easily accessible on the front panel. This front panel design allows you to tune the 30S-1 swiftly, surely and easily. With the push of a button you can switch instantly from the 100 watt power level of your S/Line transmitter to the full kilowatt output of the 30S-1; yet you retain high linearity and clean signal. The 30S-1 can also be tuned to frequencies outside of the amateur bands. Automatic Load Control voltage from the 30S-1 is fed back to the transmitter, assuring you of maximum talking power without over driving and distortion. Collins Automatic Load Control, in combination with Collins' RF inverse feedback, is a major design feature in the 30S-I which gives you more talking power with a cleaner signal than any other linear amplifier in the amateur field. The 30S-1 is a completely self-contained, single tube, grounded grid linear amplifier. The tube used is the commercially popular Eimac 4CX1000A. Correct tuning and loading are indicated by a zero reading on a full scale multimeter. The loading control and PA tuning control are simply adjusted to obtain zero meter indication. _________________________________________________________________ 30S-1 SPECIFICATIONS MODE: SSB or CW. TYPE OF SERVICE: Attended operation SSB continuous; CW 50% duty cycle. POWER REQUIREMENTS: 1115 v or 230 v, 50-60 cps, single phase, 2000 watts maximum. DRIVE POWER: 60-100 watts for full output. PLATE POWER INPUT: Nominal average, 1000 watts on SSB; 1000 watts on CW. POWER OUTPUT: 1000 watts PEP. FREQUENCY RANGE: 3.4-30.0 mc, covering 80, 40, 20, 15 and 10 meter amateur bands. By retuning input coils as necessary, the following general Coverage hands can be accommodated: FREQUENCY BAND TOTAL COVERAGE 3.5 mc 3.4- 5.0 mc 7.0 mc 6.5- 9.5 mc 14.0 mc 9.5-16.0 mc 21.0 mc 16.0-22.0 mc 28.0 mc 22.0-30.0 mc HARMONIC AND OTHER SPURIOUS RADIATION: Second harmonic -40 db; all others at least 50 db down. Third order distortion at 1000 watts PEP output 35 db below signal. NOISE LEVEL: 40 db below one tone Carrier. AMBIENT TEMPERATURE: 15 -45 C. AMBIENT HUMIDITY RANGE: 0%-90%. ALTITUDE: 0-6000 ft. SIZE: 17" W, 30-5/8" H, 18-3/4" D. WEIGHT: 160 Lbs. (72.58 kg). OUTPUT IMPEDANCE: Variable; 50 ohms nominal, unbalanced with not more than 2:1 SWR. _________________________________________________________________ Under the hood... [IMAGE] 30S-1 CIRCUITRY The power amplifier stage is a single, ceramic tetrode which is cathode driven. The grid is grounded for r-f by capacitor C104. The screen grid is connected directly to ground. The plate power supply, the screen grid power supply, and the control grid bias supply are connected in series. The junction between the plate power supply and the screen grid power supply is grounded through the screen current meter shunt. This arrangement places the cathode at negative potential with respect to the screen grid. The bias supply is connected between the cathode and the control grid. Provisions are included for r-f negative feedback to improve linearity and for automatic load control (alc) to prevent overdrive. INPUT CIRCUITS Pi-network broad-tuned circuits and the interconnecting r-f feed line match the 50-ohm input impedance to the cathode impedance, which is approximately 100 ohms. The 20.5-foot length of cable (furnished) is necessary between the 32S-1 (or KWM-2) driver and the 30S-1 input circuits. This is due to the necessity of having an even multiple of 180-degree phase shifts between driver plate and power amplifier grid. The cable length and the 30S-1 input circuits together accomplish this. An even multiple of 180-degree phase shifts is necessary because modulation components cause a change in the resistive PA cathode impedance which is translated to a shift in reactive impedance at the driver plate. The shift in reactive impedance, at the driver plate, results in phase modulation of the driver and increases the total over-all distortion of the system. A 2.5-foot additional length of cable is furnished to bring the total interconnecting cable length to 23.0 feet for use with the KWM-1 as a driver. Drive power required for maximum legal input on SSB is 80 watts PEP. OUTPUT CIRCUITS The plate circuit of the power amplifier is tuned by a pi network consisting of C120, L109, L104, C121, and C122. Capacitors C121 and C122 are ganged together and are adjustable by front panel control (LOADING) for matching the pi-network circuit to the impedance of the antenna and feed system in use. Capacitor C120 may be adjusted by the TUNING control on the front panel for resonating the tank circuit to the frequency in use. Output from the plate tank circuit is connected through the contacts of antenna changeover relay K101 to the antenna when the control circuits are switched to transmit function. POWER SUPPLY CIRCUITS Three d-c power supplies and three a-c filament supplies are included in the 30S-1. The power supply may be connected to 115-volt single-phase or to a 230-volt, three-wire,single- phase source. The 230-volt, three-wire connection is recommended. High-voltage plate transformer T201 has two primary windings. These windings are connected in parallel for 115-volt operation, and in series for 230-volt operation. The 12-volt a-c filament winding of the bias supply transformer supplies current for the filament of the alc rectifier, the pilot lamps in the two meters, and the pilot lamps which light the two dials. This transformer winding also supplies current for rectified d-c relay power. The bias winding of the transformer, T203, is connected to CR207 and CR208 in a full-wave rectifier circuit. This circuit provides grid bias voltage for the power amplifier. The heater of the 3-minute time-delay relay is supplied power from the 115-volt a-c connections which also furnish power to the high-voltage rectifier filament transformer, T202. The filament transformer, T103, supplies a-c power for the heater of the thermal over-load relay, K102. Taps on the primary of the high-voltage plate transformer, T201, are switched to provide the different voltages necessary for the power amplifier in CW or SSB operation. Power amplifier bias voltage is switched to one of two taps on the bias supply bleeder resistors for CW or SSB operation. The high-voltage plate supply rectifiers are eight, type 1N1492 silicon diodes in a full-wave bridge circuit. Each rectifier diode is paralleled with a 0.001-uf capacitor to protect it against high transient voltages. SAFETY INTERLOCK CIRCUITS The top cover and the power supply front door operate safety interlock switches for operator protection. When the top cover is opened, interlock switch S103 breaks the circuit to the coil of the plate contactor, K203. This removes all high voltages from the 30S-1. When the power supply compartment (lower) door is opened, interlock switch S205 breaks the same circuit and removes all high voltages. Both interlock switches are mechanically interlocked with shorting switches which short out the high-voltage filter capacitors at the same time the interlock circuit opens. The r-f compartment interlock switch, S102, is mechanically ganged with shorting switch S101, and the power supply compartment interlock switch, S205, is mechanically ganged with shorting switch S206. This arrangement protects the operator from accidentally coming in contact with approximately 3000 volts d-c which is present in either compartment. TIME DELAY AND STEP-START CIRCUITS When POWER-OFF switch S202 is closed, the 115-volt a-c power is applied to the heater of the 3-minute time-delay relay, K202. After the power has been applied to its heater for approximately three minutes, the bimetallic contacts close. These contacts are in series with the interlock circuits and the coil of plate contactor K202. When the ON push button is depressed, K202 is energized, contacts of K202 close and apply power to the step-start relay, K201, through d-c rectifier CR205. The large electrolytic capacitor, across the coil terminals of K201, requires a fixed charging time to rise to a potential high enough to energize the relay. When this time has passed, K201 energizes and shorts out the step-start resistors. Until relay K201 has closed, all power applied to the transformer primary winding has been dropped through the two step-start resistors, R201 and R233. Thus, the high-voltage power supply starts at low primary voltage and, after the step-start cycle has elapsed, switches to full voltage. This allows time for partial charging of the large, high-voltage filter capacitors, C207 and C208, before the application of full secondary voltage to the rectifier plates. During this time, the rectifier tubes are protected from damaging high peak currents. THERMAL AND OVERLOAD CIRCUITS The thermal overload relay, K102, protects the power amplifier tube from over dissipation and loss of cooling air. Its bimetallic strip has contacts connected in series with the interlock system. The thermal overload switch is located in the air stream from V101. Current from transformer T103 is passed through the heater of K102. This current keeps K102 temperature just below that necessary to open its contacts. If the air stream fails, the temperature of the bimetallic strip increases, opening the interlock circuit, and removing voltages from the power amplifier. If over-dissipation occurs in the plate of the power amplifier, the higher air temperature causes K102 to operate and break the interlock circuit. POWER CONTROL CIRCUITS When the POWER-OFF switch is operated to POWER position, 115-volt a-c power is applied to the filament and control circuits. If the 3-minute time delay of K202 has passed, and if all interlock circuits are in proper operating condition, the plate contactor may be energized by pushing ON switch S203. When K203 contacts close, one set of them holds the electrical connection to the coil and keeps the relay closed after the ON push button is released. Other contacts of K203 supply power to the antenna changeover relay circuit and to the primary winding of the high-voltage transformer, T201. Power to T201 is applied from K203 contacts through two step-start resistors . These resistors reduce the voltage applied to the transformer until capacitor C203 charges high enough that the voltage across it will energize step-start relay K201. When K201 closes, its contacts short out the step-start resistors and allow full voltage to be applied to the transformer winding. ALC AND R-F NEGATIVE FEEDBACK CIRCUITS Automatic load control (alc) is a type of compressor circuit, operating at radio frequencies. The modulation envelope is detected by power amplifier grid rectification. This signal is filtered of r-f by L108 and C140 and applied through transformer T102 to the alc rectifier, V203. The audio signal is rectified by V203 to produce a negative control voltage which is a function of the modulation level. The alc rectifier, V203, is connected as a voltage doubler. The negative control voltage produced by the alc rectifier is fed back to the alc line of the exciter to produce approximately 3 db of override control. The resistor, R234, in series with V203 filament, reduces the no-signal d-c level on the alc line. This no-signal d-c level is caused by the tube contact potential. If not reduced, it might cause a delay voltage to be present on the exciter alc bus. The 3 db of alc override control produced in the 30S-1 reduces the exciter r-f gain and keeps the drive level within tolerable limits. Automatic load control helps to keep the drive level low enough to prevent driving the power amplifier into distortion. A fixed amount of r-f negative feedback, from the output circuit of the power amplifier to the input of the power amplifier, produces a high degree of linearity of the amplified signal. This feedback is accomplished by capacitor C103, which couples some of the plate energy back to the grid circuit. Although there is no phase inversion between the cathode and the plate circuits of a cathode- driven amplifier, there is a phase inversion between the cathode and the grid circuit, providing the grid is not bypassed completely at the r-f frequency. Therefore, the feedback voltage is out of phase with the grid voltage. Capacitors C103 and C104 form a voltage divider circuit to maintain the proper amount of feedback voltage. TUNING & LOADING METER CIRCUIT One section of the SSB-CW switch, S201, selects the proper output voltage from the tuning and loading bridge circuit for the TUNING & LOADING meter indication. This circuit and the power amplifier tube form a specialized vacuum-tube voltmeter bridge circuit. It consists of V101, CR101A, and CR101B, and the associated load resistors and filter networks. The bridge is balanced when the plate circuit TUNING and LOADING controls are set to present the proper load impedance to the power amplifier plate. The meter then will read zero, and the power amplifier tube will be operating at the proper gain level for maximum efficiency and linearity. _________________________________________________________________ 51S-1 RECEIVER _________________________________________________________________ [IMAGE] THE COLLINS 51S-1 RECEIVER 51S-1/1A/1F/1AF/1B RECEIVER The 51S-1/1A/1F/1AF/1B Receiver receives USB, LSB, AM, and CW signals in the range of 0.2 to 30.0 MHz. Coverage is continuous in thirty 1-megahertz bands. The model 51S-1 is mounted in a perforated wrap-around cabinet and equipped with an ac power supply capable of 115- or 230-volt, single- phase, 50- to 400-Hz operation. The 51S-1A is similar, except that it is fitted with a 28-volt dc transistorized power supply. The rack-mounted ac version is model 51S-1F (figure 5-1). The rack-mounted dc version is model 51S-1AF. The 51S-1B (figure 5-2) is similar to the 51S-1, but it has a rear-mounted junction box that provides military-type connectors for power, control, audio, and antenna lines. REQUIREMENTS FOR OPERATION The 51S-1 and 51S-1F Receivers require 115-or 230-volt, single-phase, 50- to 400-Hz power at approximately 125 watts. The 51S-1B requires 115-volt, single-phase, 50- to 400-Hz power at approximately 125 watts. The 51S-1A/ 1AF Receiver requires 28 volts dc at 4.5 amperes. The 51S-1/1A Receiver may be mounted on table or bench for fixed station operation, or may be mounted with a mounting plate similar to the 351E-4 on shelf, bench, or table in moving aircraft, ground vehicle, or boat. 51S-1/ 1F/1A/1AF Receivers require a 4- or 600-ohm speaker or headphones for local audio monitoring, but monitoring devices of any impedance may be matched with 600-ohm line-to-monitor transformers at remote locations) to several miles. Alternately, the 600-ohm line termination may be connected to telephone lines, or the 600-ohm local output may be used with a phone patch. The 51S-1B has the same local audio provisions as those described above, but the remote audio line has a 150-ohm impedance. 51S-1 series receivers require a good antenna with 50-ohm unbalanced feed. _________________________________________________________________ 51S-1 SPECIFICATIONS Frequency range............ 0.2 to 30.0 megahertz in thirty 1-megahertz bands continuous coverage. Modes...................... Upper sideband, lower sideband, AM or CW. Power consumption.......... 125 watts. Type of service............ Fixed station attended with provision for remote control of rf gain. Rf input impedance ........ 50 ohms, unbalanced. 500-kHz if. output at J9... 50 mv minimum into 50-ohm load with 5-uv input signal. Matching speaker impedance. 4 or 600 ohms. Balanced line out impedance. 600 ohms balanced, center-tap ground reference or floating. (For 51S-1B, 150 ohms floating.) Matching phone patch impedance (local)........... 500 to 600 ohms. Frequency stability......... During temperature change from 0 to +50 xC, after 20 minutes warmup, audio output frequency will not vary more than +/-885 Hz for carrier frequencies from 2 to 7 MHz. From 7 MHz to 30 MHz, stability varies from 36 PPM +/-400 Hz at 7.00 MHz (652 Hz) to 27 PPM +/-400 Hz at 30 MHz (1210 Hz). For +/-10% line voltage variation, frequency varies not more than + 100 Hz. Calibration accuracy........ When zeroed to nearest 100 kHz calibration point, the frequency will be within +400 Hz. Dial backlash............... Not more than 150 Hz. Audio-frequency response AM. 100 to 2500 Hz +/-6 db (line channel). 200 to 2500 Hz +/-6 db (local channel). SSB (high-frequency limit determined by filter bandwidth)................ 350 to 3050 Hz +/-3.5 db (line channel). 350 to 3050 Hz +/-3.5 db (local channel). Audio output distortion (SSB test signal 100-microvolt input, 1.0-watt local output, 1-mv (0 dbm) line output) Local..................... Not more than 10 percent. Line...................... Not more than 1.2 percent. Q-multiplier rejection notch depth................. Not less than 40 db. Receiver sensitivity (nominal) AM........................ 3.0 microvolts for not less than 10-db signal + noise/noise (2 to 30 MHz). 15.0 microvolts for not less than 10-db signal + noise/noise (0.5 to 2 MHz). 20.0 microvolts for not less than 10-db signal + noise/noise (0.2 to 0.5 MHz). With 55G-1 Preselector, 5.0 microvolts for not less than 10-db signal + noise/noise (0.2 to 2.0 MHz). SSB and CW................ 0.6 microvolt for not less than 10-db carrier on carrier off (2 to 30 MHz). 3.0 microvolts for not less than 10-db carrier on carrier off (0.5 to 2.0 MHz). 4.0 microvolts for not less than 10-db carrier on carrier off (0.2 to 0,5 MHz), With 55G-1 Preselector, 1,0 microvolt for not less than 10-db carrier on carrier off (0.2 to 2,0 MHz). Selectivity CW (at 6 db points)....... 800 hertz bandwidth, nominal. (650 Hz minimum, 950 Hz maximum, 300-Hz maximum bandwidth optional), SSB (at 3.5db points)..... 2.75 kilohertz bandwidth (2.4 kHz bandwidth optional), AM (at 6 db points)....... 5.0 kilohertz bandwidth minimum, (at 60 db points)....... 22,0 kilohertz per second bandwidth maximum. Spurious responses (above 2 MHz) Internal spurious signals... Less than one microvolt equivalent signal. Other spurious signals...... Not less than 70 db down, except from 4.8 to 5.2 MHz, not less than 40 db down. Image response.............. Not less than 50 db down from 2 to 25 MHz; not less than 40 db down from 25 to 30 MHz; referenced to midband. Size........................ Cabinet version: 7-3/4 in. high by 14-3/4 in. wide by 14 in. deep, Rack-mounted version: 8-3/4 in. high by 19 in. wide by 15 in. deep. Weight...................... 28 pounds _________________________________________________________________ Under the hood... [IMAGE] 51S-1 CIRCUITRY GENERAL Figure 3-2 is a block diagram of the 51S-1, and figure 7-1 is a schematic diagram of the 51S-1. Figure 7-2 is a schematic diagram of the 51S-1A. Figure 7-3 is a partial schematic of the receiver, showing the complete front-end switching arrangement. The 51S-1 is a dual- or triple- conversion communications receiver which operates in the range of 0.2 to 30 megahertz. The 0.2- to 2.0-MHz portion of the coverage is intended for laboratory applications and broadcast monitoring. In this range, internally generated spurious whistles occur at 333 kHz, 666 kHz, 1000 kHz, 1500 kHz, and 2000 kHz. Triple conversion is used for the 0.2- to 7.0-MHz bands, and double conversion is used for the 7.0- to 30.0-MHz bands. For 7.0- to 30.0-MHz operation, the 14.5- to 15.5-MHz bandpass network and second mixer are bypassed. The 51S-1 is basically a 2.0- to 30.0-MHz receiver with a built-in low-frequency converter. The tuning mechanism, counter dials, and turret are arranged so the two lowest bands, 0.2 to 1.0 MHz and 1.0 to 2.0 MHz, use the 28.0- to 29.0- and the 29.0- to 30.0-MHz bands of the receiver as a variable if. (conversion) frequency. As the megahertz counter is reduced in setting below 2.0 MHz (lowest band on the turret), a segment switch, S6, connects the low- frequency converter and its bandpass filter between the antenna and the turret input, which is now the 29.0- to 30.0-MHz band. When the megahertz counter setting is reduced below 1.0 MHz, the segment switch, S6, maintains the low- frequency converter connection, but the turret is changed to the 28.0 to 29.0 MHz band. In this manner, the 28 positions of the turret plus two positions of over travel provide 30 bands, each 1 megahertz wide. The 0.2-MHz limitation of the lowest band is a function of the frequency roll-off in the bandpass filter and mixer considerations. CIRCUIT DESCRIPTIONS RF Amplifier Signals from the antenna are fed from J1 through S6 contacts to an impedance-matching transformer, L30. The output of L30 is coupled to the first section of the double-tuned input network. Refer to figure 3-1. The double-tuned input circuits are composed of C40, L33, L32, L31, C71, L69, L68, L67, and the components mounted upon turret wafers A1 through A5. All rf section components and turret wafers are shown in figure 7-3. The first section of this network is tuned by C40, Cp, Lp - Lm and L33-L32-L31. For any position of the turret, L33, L32, L31, and C40 are in the circuit, and the band changing is accomplished by connecting the turret-mounted components in shunt. The tuning slug of L32 is coupled mechanically to the tuning control of the receiver, and is varied to accomplish tuning throughout the 1-MHz band. The second section of the network is tuned by C71, Cn, Ln, Lm and L69-L68-L67. The tuning slug of L68 is ganged to the tuning control of the receiver to accomplish tuning in the same manner as that of L32 in the first section of the network. The turret-mounted components are selected by the MEGACYCLES control. This control positions the turret wafers so that the proper set of components is connected into the circuit according to the megahertz information on the counter dial. Coupling between the two sections of the input network is provided by mutual inductance Lm The output network consists of a single-tuned system using a band-switching and tuning scheme similar to that of the input network. First Mixer The first mixer, V2A, is a triode. The rf signal is fed to the grid, and the hf crystal oscillator signal is injected at the cathode. The output network consists of a 14.5- to 15.5-MHz bandpass filter for 2- to 7-MHz operation and a 3- to 2-MHz variable, triple-tuned network for 7- to 30-MHz operation. The slugs of the 3- to 2-MHz variable if. network inductors are coupled mechanically to the tuning control of the receiver and tracked with the slug-tuned inductors in the rf circuits to produce the 1-MHz coverage for each band. Second Mixer During 2- to 7-MHz operation, the second mixer, triode V3A, uses a 3- to 2-MHz variable if. for its output network. This is the same output network that is used by the first mixer during 7- to 30-MHz operation. The signal from the first mixer plate is fed through the 14.5-to 15.5-MHz bandpass filter network, T12 and T13, to the grid of the second mixer. The 17.5-MHz oscillator signal is injected into the cathode circuit of this mixer. The second mixer is inoperative during 7- to 30-MHz operation. Third Mixer The third mixer, pentode V4A, receives its input signal from the 3- to 2-MHz variable if. network. The input signal from the first or second mixer is fed to the grid of the third mixer and the vfo signal is injected into its cathode. An external vfo signal may be injected through J6 if external frequency control is desired. Such an external injection signal might also be a selected crystal oscillator frequency if precise fixed channel tuning is desired. In such a case, the tuning dial would have to be set to the channel frequency in order to properly resonate all the rf and if. gang tuned circuits. The output network of the third mixer is selected with the EMISSION switch on the front panel. In USB and LSB positions, mechanical filters FL2 and FL3, are used. These mechanical filters provide a 2.75-kHz bandwidth for single-sideband reception on upper or lower sideband, respectively. The CW position of the EMISSION switch selects a crystal filter, FL4. The crystal filter provides a 800-Hz bandwidth for reception of CW signals. The AM position of the EMISSION switch selects a network composed of two lightly coupled 500-kHz if. transformers, T14 and T15, which provides a bandwidth of 5-kHz for reception of amplitude-modulated signals. The first if. amplifier, pentode V5, receives its input signal from the third mixer through one of the four selective networks described in paragraph 3.2.4. The output signal is coupled to the Q-multiplier through if. transformer T1. Q-Multiplier The Q-multiplier, V6, is a twin triode. The first triode section is a cathode follower, the output of which is coupled to the cathode of the second triode section. When REJECTION TUNING is being used, the signal from the plate of the second triode is coupled through a parallel-tuned circuit to the grid of the second if. amplifier. The parallel-tuned circuit consists of L108, C145, and C146 and a small voltage sensitive capacitor. These components, plus R33 and R34, form a bridged-T rejection notch filter. The end of the parallel-tuned circuit, away from the plate of the second triode section, is coupled to the grid of the second triode. This feedback arrangement forms a Q- multiplier. The Q of L108 is 250. The feedback loop has a gain of 10, resulting in an overall Q of 2500 and a rejection notch depth of not less then 40 db. Turning the REJECTION TUNING control fully counter clock-wise deactivates the rejection network by forward biasing capacitance diode C315 into conduction. Second IF Amplifier The second if amplifier, pentode V7, receives its input signal from the Q-multiplier network. The output network of the second if. amplifier is if. transformer T2. The secondary of T2 is coupled to the third if. amplifier, V8, and cathode follower V11A. Third IF Amplifier The third if amplifier, V8, receives its input signal from the second if. amplifier through transformer T2. The third if. amplifier output is coupled to the product demodulator through if. transformer T3 and to the AM detector through C158. The product demodulator is composed of CR1, CR2, CR3, and CR4 in a diode-ring configuration. Signal from the beat- frequency oscillator, V17, is injected into the product demodulator at the junction of R135 and R136. The audio output is fed to the SSB/CW preamplifier, Q1. The bfo supplies a reinserted carrier to replace the suppressed carrier of the SSB signal. The demodulator functions as a mixer, and its output is a full-wave rectified signal consisting of the if. and bfo signals plus their mixing products. C161, L123, and C310 form a low-pass filter that passes the if. and bfo mixing difference frequency and blocks the rest of the demodulator output. The mixing difference frequency is the desired audio signal. SSB/CW Preamplifier The output impedance of the diode demodulator is approximately 600 ohms. Transistor Q1 provides impedance match and gain between the product demodulator and the following audio amplifier grid. The SSB/CW preamplifier is an NPN transistor, connected in a common emitter configuration. Audio signals from the product demodulator and sidetone signals from the cathode follower, V11B, are coupled to the base of Q1. The SSB/CW preamplifier output signal is coupled from the collector of Q1 through C165 to switch S2C. During SSB and CW operation, the contacts of S2C connect the audio output signal to first local af amplifier, V14B, and the first line amplifier, V14A. Audio Amplifiers The 51S-1 includes two, two-stage, audio-frequency amplifiers. The local amplifier, consisting of V14B and V12, provides audio power to local headphones, speaker, or phone patch. The line amplifier, consisting of V14A and V13, provides power for a 600-ohm remote line . The line output impedance of 51S-1B is 150 ohms. Figure 7-5 is a partial schematic, diagram of the 51S-1B output circuit. The first local and the first line af amplifiers obtain input signal from either the SSB/CW preamplifier, Q1, or from AM detector CR15. The signal source, Q1 or CR15, is selected by contacts of the EMISSION switch, S2. The first local and first line af amplifiers drive their respective second local and line amplifiers V12 and V13. The line amplifier distortion is reduced by use of negative feedback from output transformer T4 to the cathode of V14A. Low-Frequency Mixer For receiving signals in the 0.2- to 2.0-MHz range, the 51S- 1 uses a low-frequency mixer, V10A-V16A, and converts the signal to the 28-and 29-MHz bands. The low-frequency input to the mixer is passed through a bandpass filter, and the output of the mixer is tuned by the turret and slug-tuned circuits. External tuners for low-frequency operation may be used. Jacks J14 and J13 on the rear apron are provided for this use. When an external low-frequency tuner is used, the jumper between J14 and J13 must be removed. Oscillators The calibration oscillator, V16B, is a crystal-controlled oscillator operating at 100 kilohertz. Variable capacitor C227 trims the frequency of the oscillator. The output of the calibration oscillator is coupled to the antenna jack, J1. The low-frequency crystal oscillator, V10B, uses a 14-MHz crystal. The plate circuit of this oscillator is tuned to the second harmonic of the crystal. The low-frequency crystal oscillator operates only when the 51S-1 is receiving signals in the 0.2- to 2.0-MHz bands. The output of this oscillator is coupled to the low-frequency balanced mixer, V10A and V16A. Capacitor C2 trims the crystal oscillator to frequency. The high-frequency crystal oscillator, V2B, operates on all bands. Frequency of oscillator operation is determined by one of sixteen crystals mounted on a wafer in the turret (see table 3-1). The proper crystal is selected by positioning the band-switch MEGACYCLES control. Individual turret-mounted piston trimmer capacitors trim each crystal to frequency. The 17.5-MHz oscillator, V3B, is crystal controlled. This oscillator operates only when the 51S-1 is operating in the 2- to 7-MHz range. The crystal may be trimmed to frequency by variable capacitor C233. The variable-frequency oscillator is a Collins 70K-7 permeability-tuned oscillator. The frequency of this unit is varied by changing the inductance of L501. This change of inductance is accomplished by turning the 51S-1 tuning knob which is coupled mechanically to the slug of L501. The output of the oscillator tube, V15, is coupled to the cathode of the third mixer through T501. The beat-frequency oscillator, V17, is a 500-kHz crystal- controlled oscillator which operates only when the EMISSION switch of the 51S-1 is in USB, LSB, or CW position. No beat- frequency oscillator is needed for AM operation. The output of the bfo is coupled to the product demodulator. There is no provision for trimming the bfo frequency. _________________________________________________________________ 651S-1 RECEIVER _________________________________________________________________ [IMAGE] THE COLLINS 651S-1 RECEIVER Collins Radio Group's experience in the communications field, and more specifically in hf communication, dates as far back as 1933. Collins general purpose hf receiver products have set the pace for the industry throughout the years with the latest designs and highest performance. From the 51H Receiver series in the mid-1940's, through the 51J series, R-390, and 51S-1 Receivers, Collins has designed and developed hf receivers that have attained universal acceptance. In the process, Collins has developed the expertise apparent in the current 651S-1 Receiver family. The 651S-1 Receiver has potential uses not possible for any receiver previously developed in the long line of Collins products. Handsomely styled, this unit is as suited for an executive's office as it is for a remote, unattended communications site. The 651S-1 Receiver series was developed and produced by Collins in late 1970 to meet the need for a remotely or locally controlled state-of-the-art general purpose hf receiver capable of reproducibility in high volume and at an economical cost. It was designed using modular, solid-state construction for ruggedness, reliability, maintainability, cost effectiveness. and flexibility of configuration for various functional applications. Optional functions, such as ISB, vlf, special if filter bandwidths, and various remote control interfaces were designed to be added by the simple insertion or substitution of plug-in modules. This flexible characteristic gives the 651S-1 the capability of being molded to meet specific customer requirements with minimum effort, minimum design changes, and minimum cost to the customer. The latest in the 651S-1 Receiver family is the 651S-1B configuration which incorporates a highly stable plug-in digital VBFO function, plug-in RS-232C/MIL-STD-188C computer interface, and a completely modular plug-in power supply. It can also be provided with a continuous 10-Hz tuning capability by combining the tuning functions of the digital VBFO and main receiver tuning. Extensive domestic and international evaluations of various configurations have convinced many of our customers to classify this receiver family as standard. A typical example is the US Coast Guard, which has selected the 651S-1 as their standard general communications receiver. In addition, the Coast Guard is also using the 651S-1, with much success, in severe environment aboard patrol boats. Another example is the US Air Force which has placed the 651S-1 in inventory under FSN 5820-141-8976. One application is the Tactical Weather System "C", Module AN/TCC-77, which uses three 651S-1 Receivers per module. It was in this system that the 651S-1 was first placed in the Air Force inventory after passing severe environmental evaluations per MIL-STD-810B and MIL-S-52059B without experiencing a failure, while installed in the shelters. A large number of 651S-1's have also been procured by US Government organizations for numerous applications ranging from single-receiver installations to elaborate processor-controlled systems. Response from all customers, in the US Government and internationally as well, has been extremely favorable, with good reports on the receiver design, performance, and reliability. Such acceptance fully demonstrates the quality of the 651S-1 Receiver family and Collins dedication to customer requirements, service, and support. The typical systems described in this document have been designed for various customers using equipment from our proven product lines and from those of sub-contract firms from which we have satisfactorily acquired equipment over a number of years. Requirements for new equipment design and development for such systems are held to an absolute minimum. System engineering activities of this type are accomplished by the Telecommunications Equipment Division of Collins. This division, located in the largest engineering and manufacturing center of Collins, is devoted exclusively to the design, development, manufacture, and application of hf and uhf communications equipment and systems of the type described in this document. Description The 651S-1/1A/1B is a triple-conversion superheterodyne receiver that provides continuous coverage of the 250-kHz to 29.9999-MHz frequency range. It is a completely solid-state desk-top or rack- mounted receiver and features direct-reading digital display of the operating frequency. The frequency range can be easily extended down to 12 kHz for vlf operation by the simple substitution of plug-in modules. Many other options are available, such as various remote control interfaces, narrow-band FM, independent sideband, and special filters; with each capable of being incorporated by the simple addition or substitution of plug-in modules. Information on these and other options is presented later in this document. The 651S-1( ) provides reception of AM, ISB (independent sideband), USB, and LSB. The receiver is also compatible with RTTY and NBSV (narrow-band secure voice) modems. Designed for a variety of applications, this capability may be extended to meet specific requirements through the use of the many available options. Excellent frequency stability is obtained through the use of a frequency synthesizer that is phase locked to a temperature-compensated crystal oscillator. Two rotary switches provide coarse frequency adjustment in 1- and 0.1-MHz steps while a main tuning control varies frequency smoothly in 100-Hz increments with 10-kHz frequency change per revolution. Continuous coverage of the entire frequency range using only the main tuning control is possible without the need for band switching. For frequency interpolation between the 100-Hz steps, the VBFO may be used to adjust in 10-Hz steps over a 60-Hz range in SSB mode and in 150-Hz steps over a 900-Hz range in CW mode. A VBFO continuously tunable in 10-Hz steps over a +/-9990-Hz range with the VBFO frequency displayed on the front panel, is also available in the 651S-1B. In addition, a version of the 651S-1B can be provided with the digital VBFO and main tuning combined, thus giving tuning capability over the entire frequency range in 10-Hz steps. In this configuration the VBFO steps nine increments (or 90 Hz) after which it is reset to zero and the main tuning is stepped one increment (or 100 Hz). This sequence is then repeated as the sweep tuning knob is rotated. Seven-bar indicators display selected frequency to six digits for rapid, accurate readout. All front panel controls except POWER, METER, AF GAIN, and DIAL LOCK can be remotely controlled when using the proper remote accessories. _________________________________________________________________ 651S-1 SPECIFICATIONS FREQUENCY RANGE: 250 kHz to 29.9999 MHz in 100-Hz increments (12 kHz to 29.9999 MHz optional). FREQUENCY CONTROL: Phase-locked to internal standard oscillator (phase- locked to an external standard, optional). FREQUENCY STABILITY (with fixed bfo): 5 parts in 107 over any 30-day period if held within specified environmental limits. 1 part in 108 per week, typical, with constant temperature (drift rate). Stability of external standard when used. FREQUENCY ADJUSTMENT: 100-Hz steps by continuous tuning control or optional 10-Hz steps on 651S-1B by continuous tuning control with VBFO and main tuning function combined. 1- and 0.1-MHz steps by rotary switches. MODES: AM, SSB, and CW. ISB and NBFM provided as options. RTTY and NBSV when using external modems. BANDWIDTH (standard 651S-1): AM: 16, 6 kHz, USB: 2.7 kHz (see optional configurations description for additional bandwidths). BANDWIDTH (651S-1A): AM: 3, 6, 16 kHz, USB: 2.7 kHz, LSB: 2.7 kHz, CW: 370 Hz, 500 Hz, and 1.1 kHz. (Additional bandwidths are available on request.) BANDWIDTH (651S-1B): AM: 16, 8, 4 kHz; USB: 2.7 kHz; LSB: 2.7 kHz; CW: 0.5, 1.0, 2.0 kHz. (Additional bandwidths are available.) ANTENNA INPUT IMPEDANCE: 50 ohms, nominal, unbalanced (may be strapped to 1000 ohms on vlf option). SENSITIVITY (for 10 dB (s+n)/n): 0.250 to 0.4 MHz: SSB: 5 uV (2.7-kHz bw). AM: 35 uV (6-kHz bw). 0.4 to 2.0 MHz: SSB: 2.5 uV (2.7-kHz bw). AM: 10 uV (6-kHz bw). 2.0 to 29.9999 MHz: SSB: 0.7 uV (2.7-kHz bw). AM: 3.5 uV (6.0-kHz bw). NBFM (optional) 1.0 uV (12.0 dB SINAD). 12 to 559.9 kHz (50-ohm input with optional vlf converter): SSB: 2.5 uV (2.7-kHz bw). AM: 12 uV (6-kHz bw). REJECTION OF EXTERNAL SIGNALS: If feedthrough: -80 dB. If image rejection: -80 dB. Crossovers and noise modulation: -80 dB (interfering signal at least 15 kHz removed). CROSS MODULATION (-10 dB, 30-percent modulation with 50-uV desired signal): +50 kHz from operating frequency: 0.35 V. +10 percent from operating frequency: 0.50 V. SPURIOUS RESPONSE, INTERNAL: Not more than 2 ,uV equivalent except for four discrete frequencies (0.9, 9.9, 19.8, and 20.7 MHz), which are not more than 10 uV equivalent. INTERMODULATION DISTORTION IN BAND: -40 dB, third order at 100 mV per tone. INTERMODULATION DISTORTION OUT OF BAND: Second order - Two equal signals +26 kHz or more removed from wanted signal shall be at least 77 dB relative to one microvolt in order to produce equivalent input signal of one microvolt. Third order - Two equivalent signals +26 kHz or more removed from wanted signal shall be at least 80 dB relative to one microvolt to produce equivalent input signal of one microvolt. With optional half-octave filters--Second order product improved to 90 dB relative to one microvolt to produce equivalent input signal of one microvolt. Third order product remains unchanged except half-octave filters reduces receiver front-end exposure to strong signals outside the filter bandpass. AUDIO OUTPUTS: 8-ohm speaker output; 600-ohm headphone output; 600 ohms, balanced, center tap grounded or floating. Also, 600-ohm output for ISB channel. GAIN: In SSB, 3 uV produces 0.5 watt of audio into 8-ohm load or 1 mW (0 dBm) into 600-ohm line output. AUDIO LEVELS AND DISTORTION: 2-watt. 8,0-ohm output at not more than 3-percent total distortion. 5-mW peak (+7 dBm), 600-ohm line output, at not more than 1-percent total distortion. 6 mW at 600 ohms headphone output for not more than 3-percent distortion. AUDIO RESPONSE (600-ohm line audio): Within 1 dB from 100 Hz to 4 kHz. (If filter response will further modify overall receiver response; example, 2.7-kHz SSB filter response is -3 dB at 350 and 3050 Hz.) AUDIO HUM AND NOISE: At least 40 dB below maximum output. AUTOMATIC GAIN CONTROL: Audio rise: Not more than 6 dB from 3 uV to 0.3 V. Attack time: 2 ms, nominal. Release time: 100 ms (fast) or 1 s (slow), nominal. IF OUTPUT: 50 mV at 450 kHz, 50-ohm load; same for the ISB channel. BFO (fixed and variable): Fixed: Bfo is phase-locked to internal standard oscillator in the 651S-1/1A/1B. Variable: In the 651S-1/1A, bfo in CW mode, tunable +/-900 Hz in 150-Hz steps; in SSB mode, tunable +/-60 Hz in 10-Hz steps to interpolate between 100-Hz positions. In the 651S-1B, bfo in all modes tunable +/-9990 Hz in 10-Hz steps to interpolate between 100-Hz positions. ANTENNA INPUT PROTECTION: Overload diodes protect all circuits up to 10 Vrms. METERING: Front panel meter indicates rf input signal level in decibels above 1 volt or 600-ohm audio line level in dBm. RELIABILITY: Predicted 7600-hour mean time between failures (MTBF) in a fixed-station ground environment and with temperature, shock, and vibration within environmental limits specified. An actual MTBF in excess of 80,000 hours was demonstrated between July 1973 and January 1974 by the US Coast Guard on 378 units, which they had deployed in a controlled fixed-ground environment having relatively controlled temperature and minimal shock and vibration. ENVIRONMENTAL: Temperature: 0 to +55 xC for full performance. Humidity: 90 percent. Altitude: 10,000 feet. Shock: Bench handling test per MIL-T-4807, method 4A. A basic configuration of 651S-1 Receiver, hard-mounted to an equipment rack in a US Air Force Tactical Weather Shelter ("C" Module AN/TCC-77), has successfully passed the temperature, humidity, and shock test specified in MIL-STD-810B and MIL-S-52059B. Operating power requirements for the 651S-1( ) are 115/230 volts +10 percent, 47 to 63 Hz, 70 watts. Up to 40 watts additional power may be required when options are implemented. _________________________________________________________________ Under the hood... [IMAGE] 651S-1( ) CONFIGURATIONS Three types of the basic 651S-1 Receivers have been manufactured by Collins evolving to the current configuration now in production. In addition, two special receivers, the 651S-1A and 651S-1B, each of the more recent series, have been produced. For identification purposes, each of the three basic receivers has different last three digits (status) of the Collins part number, -002 series, -102 series,.and -152 series. In the process of the evolution, receiver module interchangeability has been a constant consideration. As a result, all the modules in the current -152 series and the 651S-1A are interchangeable with those of the older -102 series receiver. The same is true of the older -002 series receiver, with the exception of one module, the DCFE. Although it differs more functionally, many of the modules of the 651S-1B Receiver are also interchangeable with older receivers. The 402 series was the first production 651S-1. The -002 status is the basic manual receiver. Status endings -002 through -019 are -002 derivatives, and are no longer in production. The -002 series receiver is documented in an earlier 651S-1 instruction book, Collins part number 523-0763090, dated 1 July 1971. The-102 Series: The -102 series was the second production series and had some minor configuration changes from the -002 series; the mode and bandwidth functions were separated, and audio squelch was deleted as a standard feature and made optional. The -102 status is the basic manual receiver and has an FM detector, a 500 Hz CW filter, rf input 1/2 octave filters, frequency memory keep alive circuit, and preselector control connector (J63). Statuses -102 through -136 are -102 derivatives and are no longer in production. The -102 series receiver is documented in the 651S-1/1A basic instruction book Collins part number 523-0764052. The-152 Series: The -152 series is the latest version of the 651S-1 Receiver. The keep-alive circuit. preselector control connector (J63), FM detector, 500-Hz bandwidth if filter, and 1/2-octave filters are deleted, but can be added back as options. All statuses above -152 are derived from the basic -152. The various configuration options of the 651S-1 Receiver (-152 series) are shown in table 1. Configuration of special purpose receivers 651S-1A and 651S-1B are shown in table 2. To determine what configuration options are installed in a specific 651S-1 Receiver, locate the Collins part number in the 651S-1 part number column of table 1: Columns to the right indicate which chassis and plug-in circuit cards/modules are installed in that particular status of receiver: columns to the left show what options are incorporated in that particular receiver. For added information on the basic 651S-1 Receiver and all available plug-in modules refer to the 651S-1/1A Instruction Book Collins part number 523-0764052. The 651S-1 configuration options currently available are briefly described in the following paragraphs. VLF CONVERTER Provides low-frequency reception by extending the lower frequency limit to 12 kHz. Two subassemblies are replaced to obtain vlf coverage, rf module A6 and synthesizer divider card A10. Refer to the configuration chart for the status numbers of receivers that already have the option installed and for part numbers of the vlf subassemblies. INDEPENDENT SIDEBAND (ISB) Permits independent reception of upper and lower SSB signals; and contains if amplifier, detector, and line audio amplifier. Independent sideband operation is obtained by the addition of an ISB plug-in circuit card (A3). AUDIO FREQUENCY SQUELCH Provides audio frequency squelch that is adjustable on a signal-to-noise basis. To obtain this option the AF GAIN control on the front panel is replaced with a combination gain/squelch control; in addition, the plug-in audio card (A2) is replaced with an audio card with squelch circuits. Refer to the configuration chart for the status numbers of the receivers that have the squelch option already installed and the part number of the audio card that has the optional squelch circuits. NARROW-BAND FM (NBFM) Permits reception of narrow-band FM signals. To obtain this option, the standard if amplifier card A4 is replaced with an if amplifier card containing the FM detector. Refer to the configuration chart (table 1 for the status numbers of receivers that have the NBFM option installed and the part number of the if amplifier card that has the FM limiter/detector circuits. FREQUENCY SCAN Provides an automatic sweep of frequencies in 100-Hz increments to a maximum range of 100 kHz with dwell time (period in which the receiver remains on a discrete frequency) variable from 100 to 600 milliseconds. Sweep range and dwell time are selected internally by strapping the frequency scan card or externally with the use of an associated 775L-1 Local Scan Control Unit. To obtain this option a frequency scan card is added. EXTERNAL FREQUENCY STANDARD Allows the use of an external 100-kHz, 1-MHz, or 5-MHz frequency standard. This option is obtained by replacing the normal synthesizer frequency reference card (A11) with a new card. Refer to the configuration chart for part number of the new card. This option can be added to any 651S-1 Receiver. FREQUENCY MEMORY KEEP-ALIVE POWER Used to maintain storage of frequency information during power interruptions. An external 6- to 8-volt battery supplies the necessary power for the circuit. This option is implemented by wiring the special keep-alive assembly into the chassis subassembly. Refer to the configuration chart for status numbers of receivers that include this option and for the part number of the chassis subassembly that includes the special keep-alive power assembly. IF FILTERS Some of the if filters available as options are listed below. Installation consists of placing the appropriate filter on the optional if filter piggy-back card. Additional filter options are available upon request. Refer to the configuration chart for status numbers of receivers that include available filter options and for the part numbers of the various filter cards. BANDWIDTH (kHz) USE 0.2 CW 0.370 RTTY 1.0 CW 3.0 AM 1.1 RTTY 0.5 CW TELETYPEWRITER REMOTE CONTROL Provides the proper interface between the 651S-1 and a 514S-1 Remote Control Unit. The control interface between the 514S-1 and the 651S-1 is a 20-mA neutral TTY loop, using ASCII coded characters. A printer control unit (TCU) plug-in card and a device control functional element (DCFE) plug-in card are added to implement this option. Refer to the configuration chart (table 1) for status numbers of receivers that include this option and for part numbers of the plug-in cards. COMPUTER REMOTE CONTROL Provides control interface for processor control of the 651S-1 Receiver. Several different processor control interfaces can be implemented in the receiver by the addition of the appropriate device control unit (DCU) and device control functional element (DCFE) plug-in cards. Interfaces available include the serial CCCS 4800-bit and 76.8-kb configurations for use with the Collins processors, and a 75 to 19,200 baud RS-232C/MIL-STD-188C configuration for use with commercial processors. Refer to the configuration chart for status numbers of receivers that include this option and for part numbers of the plug-in cards. _________________________________________________________________ KWM-380 TRANSCEIVER _________________________________________________________________ [IMAGE] THE COLLINS KWM-380 TRANSCEIVER The Rockwell/Collins advertisements for the KWM-380 contain a nostalgic scene with some S-Line gear. It makes for a nice advertisement display, but no one should imagine that the KWM-380 has anything in common with the old S-Line gear except a bit of nostalgia. The KWM-380 is a completely new transceiver concept from the ground up. The KWM-380 h.f. transceiver makes quite an impression when one first receives it as I did in a rather huge package. Unpacking it, one finds a unit that measures about 16 " X 18" X 7 " and weighs in at almost 50 Lbs. For its power class as a nominal 100 watt output transceiver, it is several times larger and/or heavier than quite a few transceivers on the market, although one should note that it is a complete station package. That is, it contains a speaker, power supply, the equivalent of a second v.f.o., and space for a host of accessory items, such as a unique type of new speech processor. The space and weight involved is not wasted. The transceiver is filled with circuitry and interesting features, as it should be for its price class. The transceiver basically covers the 1.8 to 30 MHz range in 10 Hz steps with a four-speed tuning capability on receive and nominally only the 160-10 meter amateur bands on transmit. WARC bands are provided for by a simple modification. The receive coverage is not specified in terms of "bands," because from an operating viewpoint they do not exist. The tuning coverage is truly continuous, in that, as described later in more detail, one simply rotates the tuning knob to go from 1.8 to 30 MHz. There is no bandswitch nor any receive or transmit tuning controls other than the main tuning knob. The rest of the specifications call for very "tight" frequency readout accuracy and stability, a nominal 100 watt output, very good unwanted signal suppression values on transmit, and an exceptional combination of good receive sensitivity with a +15 dBm third-order intercept point. Just reading through the specifications, one senses that the KWM- 380 should be an exceptional transceiver. The physical impact of the KWM-380 only serves to enforce this expectation - not because of its weight, but because of its exceptionally "clean" panel layout and extremely clear and large digital frequency display. As it turns out, the KWM-380 is an exceptional piece of equipment. Someone such as myself who enjoys understanding and writing about circuitry detail could probably generate several volumes on the KWM-380. However, I'll try to resist over-indulgence in that aspect of things in favor of giving you a general description of the electrical concept of the KWM-380, while highlighting a few specific circuits, some comments on the KWM-380's physical make-up, results of test measurements, operating impressions, and finally, details on a few of the most interesting accessories available for the KWM-380. _________________________________________________________________ KWM-380 SPECIFICATIONS Parameter Specifications Physical Size 394 mm (15.5 in.) wide; 190 mm (7.5 in.) high, inc. 25 mm (1 in.) feet; 457 mm (18.0 in.) deep. Weight 27.2 kg (50 Lb.), max Environmental Operating temperature 0 to 50xC (32 to 122xF) Operating humidity 0 to 90% relative humidity Operating altitude 0 to 3049 m (0 to 10,000 ft.) Vibration 2 g's, 10 to 33 Hz Electrical Primary power Strappable for: 105,115,125/210, 220, 230, 240, 250 V + 5%, 50 to 60 Hz; or 12 to 15 V dc, negative ground:120 watts max in receive, 600 watts max in transmit Receiver Frequency 0.5 to 30.0 MHz, tunable in 10 Hz steps Modes u.s.b., l.s.b., a.m..and c.w. Sensitivity (Soft uV 0.5 pV or better for 10 dB (s+n)/n, 2.0 to 30.0 MHz, measurement) s.s.b. and c.w.; 1.0 uV or better for 1.8 to 2.0 MHz. Selectivity (3 dB Selectable: bandwidth) 8 kHz *1.7 kHz *6 kHz *360 Hz 2.1 kHz *140 Hz *Optional Filters I.F. and image rej Greater than 60 dB Intermod distortion -50 dB or better for two signals of -10 db mW each, 20 kHz apart AGC Audio output variation not more than 8 dB for 4 uV to 200 mV open circuit r.f. input variation Audio output Not less than 3 W into 4 ohm load, at 1 kHz, at not more than 10% total harmonic distortion Line audio output not less than -10 dB mW nominal in to 600 ohms Frequency response: 300 to 2400 Hz with not more than 5 dB variation Transmitter Frequency 160 through 10 m amateur bands, in 10 Hz steps 160 m 1.800 to 2.000 MHz 80/75 m 3.500 to 4.000 MHz 40 m 7.000 to 7.300 MHz 20 m 14.000 to 14.350 MHz 15 m 21.000 to 21.450 MHz 10 m 28.000 to 29.700 MHz Modes u.s.b., l.s.b., and c w. (RTTY by AFSK on l.s.b.) Output power 90 W pep, min (100 W, nominal) In c.w. or RTTY: 50% duty cycle; key down 15 minutes, max. Automatic turndown to 50 W after 10 seconds. With optional blower kit installed, power is 100 W average, 50% duty cycle, key down 1 hour max at 25xC; 30 minutes max at 50x C for all modes. Unwanted sig suppression Carrier -50 dB or better Undesired sideband, 1 kHz ref -55 dB or better Harmonics (all) -40 dB or better Mixer products -50 dB or better Third order distortion 25 dB below each tone of 2-tone test Synthesizer accuracy Accuracy within + 5 Hz after 10 minutes warmup when and stability 39.6 MHz and 455 kHz oscillators are set to within +/- 3 Hz. Stability within +150 Hz over temperature range of 0 to 50xC (32 to 122xF) if oscillator's set within 10 Hz at 25 xC (77 xF) Antenna Impedance 50 ohms, nonreactive. (Full transmitter power output with v.s.w.r. of 2:1 or less. Automatic power output turndown with v.s.w.r. greater than 2:1.) Audio inputs Microphone Low or high impedance, dynamic; 3.3k nominal impedance Line 600 ohm, unbalanced; 40 mV input sufficient for full r.f. power output _________________________________________________________________ Under the hood... [IMAGE] KWM-380 CIRCUITRY The receive and transmit signal chains do utilize some common circuits, but if one notes the arrows on the diagram for their signal flow, one can separate them fairly well. For instance, the receive signal path starting at the antenna (upper left corner) goes through a low-pass filter and a.g.c. blocks to a first mixer stage. This mixer stage receives local frequency injection in the range of 39.145.00 to 69.144.99 MHz from a synthesizer block and produces the first i.f. output at 39.145 MHz. The 39.145 MHz i.f. signal goes through a broad 4-pole crystal filter and on to the second mixer, which produces the second i.f. frequency of 455 kHz. The i.f. frequency is translated to 6.255 MHz in a passband tuning circuit and then retranslated back to 455 kHz. The final 455 kHz signal is routed through a product detector for s.s.b./c.w. or to an a.m. detector and then on to a c.w. audio filter and the a.f. amplifier stages. The transmit signal path starts with a balanced modulator at 455 kHz (upper right of fig. 1), goes through the sideband filter associated with the 6.255 MHz passband tuning circuit, is retranslated to 455 kHz, then is up-converted to the 39.145 MHz i.f., and finally is translated in the same mixer which handles the incoming receive frequency to the output frequency. All of the frequency conversions used in the KWM-380 may seem a bit confusing, but they are designed to accomplish various specific functions. An examination of slightly more detailed receive and transmit signal path block diagrams should help to clarify the situation. The "front-end" of the KWM-380 is unique in several respects. There is no r.f. amplifier stage, and there are none of the usual bandpass filters as are usually associated even with transceivers having a "high" first i.f. (above 30 MHz). The filter blocks that an incoming signal goes through before being amplified are not quite what one would expect. The first filter block is a 0.5-1.6 MHz roll off one, simply designed to protect the transceiver from BC band overload. The high-pass filter block works in conjunction with a following 30 MHz low-pass filter block. The latter is fixed in frequency at 30 MHz, while there is a selection of three high-pass filter cutoffs of about 20,14, or 7 MHz. So, an incoming signal can be "bracketed" between 7-30 MHz, 14-30 MHz, or 20-30 MHz. The reason for this arrangement is not simply to provide image signal rejection; the very high first i.f. frequency takes care of that. The high-pass filters ensure that the transceiver does not generate second order intermodulation products of commercial/broadcasting stations. For instance, in the European area the "breakthrough" of 13-15 MHz signals on "simple" transceivers operating on 10 meters can be a very severe problem. The problem doesn't exist with the KWM- 380. In between the high and lowpass filter blocks one can see a PIN diode attenuator (CR104). This diode is controlled by a voltage from a.g.c. amplifiers in the KWM-380. Essentially, the diode performs the same function in an automatic fashion as the manual r.f. attenuator switches one finds on many h.f. transceivers. The 39.145 MHz i.f. signal is produced by the first "U100" mixer. This i.f. signal is amplified, passes through an optional noise blanker unit, and then goes on to mixer "U102," where the i.f. signal is translated to 455 kHz and routed to a passband tuning assembly. An up/down frequency translation takes place in this assembly in that the 455 kHz i.f. is translated to an i.f. of 6.255 M Hz and then back down again to 455 kHz. True signal selectivity takes place in crystal filters associated with the 6.255 MHz i.f. The final 455 kHz i.f. signal is demodulated to provide an audio output and rectified to provide the control voltage for an elaborate "hang" a.g.c. loop which controls both the incoming signal attenuation (PIN diodes between the high- pass and low-pass filter blocks) and the final 455 kHz i.f. signal attenuation (PIN diodes before the "U700" stage). The 800 Hz Spot Tone input shown in the lower left-hand corner of fig. 2 provides for a convenience feature, in that in the c.w. mode only, one can enable an 800 Hz test tone to which a received c.w. tone (centered on 800 Hz by a c.w. i.f. filter) can be matched for exact transmit/receive frequency coincidence. It would be fun to highlight in detail numerous unique circuits used in the KWM-380. However, if one has to use a practical approach by both serving potential purchasers of the KWM-380 and giving readers some circuit ideas, the following should be of special interest. The basic "front-end" of the KWM-380 is shown in fig. 3. This diagram shows in detail and with circuit values the various filter sections previously mentioned. The antenna signal first encounters the multiple-pole BC band rolloff filter shown as L800-804 and C800-801. The three high-pass filters are each composed of a similar number of components (e.g., five capacitors and two inductors). The 100 uh coils on each side of each filter are RFC's which are used for signal isolation in the PIN diode switching scheme used. When point K(7) is grounded, the filters are bypassed by diodes CR800-801. When one of the points L(7), M(7), or N(7) is grounded, one of the three filters is selected. The incoming signal then passes on to the diode section between C825-C102. This diode section is an overload protector composed of zener diodes VR100-101 and limit at the 7 volt level. C104 is switched to ground by the variable resistance of PIN diode CR104, which in turn is driven by the chain of a.g.c. amplifiers shown at the bottom of this diagram. The incoming signal then goes through the fixed 30 MHz low-pass filter and on to mixer U100. U100 is a commercial diode ring mixer (type SRA1H from Mini-Circuits Lab., Brooklyn, N.Y. 11229). The signal is, of course, then translated to the first i.f., but note that only then does signal amplification take place. The whole "front-end," so far, has been passive. The concept and practical usage of the passband tuning used in the KWM-380 is illustrated in fig. 4. The 455 kHz signal coming into mixer U4 has a bandwidth up to 8 kHz. After mixing, the resultant 6.255 MHz signal is routed to any one of five crystal filters: a standard s.s.b. filter (2.1 kHz), standard a.m. filter (8.0 kHz), an optional narrow filter for s.s.b. (1.7 kHz), or optional narrow filters for c.w. (140 or 360 kHz). One also has the option of physically substituting an optional 6.0 kHz filter for a.m. for the standard 8.0 kHz one. These filters are all switched in and out by some diode/transistor switching circuitry as controlled by the front-panel selectivity control. The 6.255 MHz signal is then retranslated to 455 kHz in mixer Q1. Since mixers U4 and Q1 have a common injection oscillator, varying the frequency of that oscillator moves the selected filter bandwidth chosen within the overall incoming 8 kHz bandwidth of the incoming 455 kHz signal. It shows the passband tuning effect as one varies the passband tuning control when a standard s.s.b. filter has been selected. Two things should be noted: the filter bandwidth does not vary as its placement is varied, and the operator must set the passband tuning control so either l.s.b. or u.s.b. signals are passed. One can note that the microprocessor control block commands a central position as regards accepting input commands from the frequency tuning controls and then sending out data to various blocks such as those for the synthesizer, frequency display, and high-pass and low-pass filters. The CPU itself is a type 6802. There would be no point in going into all the complex circuitry within the microprocessor and its associated blocks. For example, there are several complex PLL loops within the synthesizer. But, the general concept of control exercised by the microprocessor is interesting. It accepts tuning information from the main tuning knob via photo-choppers and senses if the tuning knob rotation is up or down. It also accepts tuning rate control information from switch settings. It then supplies this data to the synthesizer for frequency generation in 10 Hz steps and to the frequency display for readout to 10 Hz steps. When certain frequency limits are reached, it sends controls to diode switch in or out highpass filters in the receive signal chain and relay switch low-pass filters in the transmit signal chain. Frequency set information is stored for the two AIB v.f.o.'s in the KWM-380 during operation, and the two frequencies can be anywhere within the operating range of the transceiver. However, when power is turned off and then turned on again, the v.f.o.'s are always reset to 15 MHz. The frequency generation and control is arranged such that frequency coverage is continuous without any break for "bands." That is, if the fastest tuning rate is chosen, three revolutions of the tuning knob will completely set the transceiver on any desired frequency between 3.000.00 and 29.999.99 MHz (receive mode, transmit mode is limited to amateur band segments). The other selectable tuning rates are 200 kHz, 20 kHz, and 2 kHz for one main tuning knob revolution. Details of the transmit chain in the KWM-380. The basic modes generated are s.s.b. and c.w. For s.s.b. generation a d.s.b. signal is generated at 455 kHz in balanced modulator U501. The signal is then routed through the 2.1 kHz filter contained in the passband tuning circuit used on receive and translated again to 455 kHz as an s.s.b. signal. On transmit, a front-panel mode switch automatically sets the variable oscillator in the passband tuning circuit so a selected l.s.b. or u.s.b. signal is generated. In this manner, and considering the action of the passband tuning control on receive, one has independent control of sideband selection for transmit/receive. The 455 kHz s.s.b. signal is further frequency translated up to the final operating frequency by the same mixer/oscillator circuits active in the receive mode. The signal reaches the 100 mW level in broadband amplifier stage Q202-204 and is fed on to a power amplifier block. For c.w. operation, the 455 kHz carrier signal normally injected into the balanced modulator is diode switched into the 455 kHz i.f. chain preceding the passband tuning block. This 455 kHz carrier signal is also gated for c.w. keying by a diode switch, Q503, which is controlled by a pulse shaping circuit, U500C, which provides for controlled rise and decay times during c.w. keying. The c.w. keying circuitry also activates a sidetone oscillator feeding the microphone preamplifier stage. This is provided so the VOX circuitry can also be used on c.w. for receive/ transmit switching. The sidetone output is not used to generate a c.w. carrier. The VOX circuitry provides for separate "delay" control settings in the c.w. and s.s.b. modes. On both s.s.b. and c.w. the output level essentially can be adjusted for QRP levels to full output. On s.s.b. this is accomplished by control of the microphone amplifier gain and on c.w. by circuitry which directly controls the r.f. carrier level via controlled biasing of the a.l.c. loop. Metering provides for monitoring the a.l.c. level, using the same scale as for S readings on receive, and for direct reading of forward and reflected power levels as sampled at the output of the power amplifier. November 1982 CQ Reviews: The Rockwell-Collins KWM-380 Transceiver by John J. Schultz - W4FA _________________________________________________________________ KWM-380 Accessories AC-2801 19" rack mount AC-2827 Telegraph key AC-2828 Microphone foot switch AC-2829 Standard headphones AC-2830 Light-weight headphones AC-3801 Noise Blanker AC-3802 Speech Processor *AC-3803 Control Interface AC-3804 AM Update Kit AC-3805A Keyboard Frequency Entry AC-3807 High Stability Oscillator AC-3808 General Coverage Option Kit AC-3809 Adapter Connector AC-3810 360 Hz CW filter AC-3811 CW Filter AC-3812 1.7 KHz narrow SSB filter AC-3813 6.0 KHz AM filter MM-281 Noise-canceling hand mike SM-281 Noise-canceling desk mike * SB-1 Make control Interface compatible with the CU-380 _________________________________________________________________ KWM-380 Service Bulletins SB-1 Change mike impedance SB-2 Improve transmit spectral purity SB-3 Superceeded by SB-16 SB-4 Replace optical encoder SB-5 Improve AF/RF pot tapers SB-6 Correct transmit hum SB-7 Reduce receiver birdies SB-8 Improve receiver AGC action SB-9 Stop PA oscillations SB-10 Add WARC band transmit SB-11 Add receiver low pass filter SB-12 CW waveshape improvement SB-13 Improve receiver AGC action SB-14 Insure transmit audio response SB-15 Add anti-static discharge path SB-16 Improve frequency synthesis SB-17 Add external tune line for CU-380 SB-18 Eliminate RF pulse _________________________________________________________________ ARTHUR A. COLLINS - BIOGRAPHY Founder of the Collins Radio Company _________________________________________________________________ [IMAGE] Arthur A. Collins - WXCXX ... 1909-1987 _________________________________________________________________ "A Young Radio Enthusiast" Reprint of Chapter One "The First 50 Years ... A History of Collins Radio Company" by Ken C. Braband Communications Dept., Avionics Group, Rockwell International, Cedar Rapids, Iowa - Copyright 1983 Early amateur radio operators were mainly hobbyists, but there was a sense of discovery during the infancy of radio that provided something more. Radio was the new thing, comparable to what computers mean to technological whizzes in the 1980s. And like the computer hobbyists of today who are writing their own programs and building their own equipment, amateur radio operators in the 1920s were contributing to the knowledge of practical aspects of radio art. One person caught up in the excitement of radio was Arthur Andrew Collins. Born in Kingfisher, Oklahoma, on Sept. 9, 1909, Collins moved to Cedar Rapids, Iowa, at an early age when his father, Merle (or M. H. as he preferred to see it written), established The Collins Farms Company there. With the Collins Farms Company, M. H. Collins brought new ideas to the stoic profession of farming. The elder Collins reasoned that the efforts of scientists and engineers could do for farming what they did for nearly every other industry in America. "Why not manufacture food for the American consumer as cheaply as motor cars and radios are manufactured?" M. H. asked in a publication which explained his new ideas. "Why not produce food on a large scale by intensive farming methods in Iowa, where high yields could be obtained and at a low cost?" The primary object of the farm company was to produce grain at low cost. M. H. Collins felt that too many farmers mixed grain production with livestock raising, and as a result, both were unprofitable. He implemented his plans by convincing landowners he could improve the profitability of their tenant farms. Farms of 160 to 320 acres were planted to a single crop and were rotated as a single tract in a unit group of farms, each embracing 1,500 to 2,000 acres. Each unit of contiguous farms was put under the supervision of a salaried foreman who directed the tractor operators. The most modern machinery was employed for every operation - four-row cultivators rotary hoes, deep disc plows, two-row corn pickers, fast trucks for marketing crops, and semi-trailers for moving machinery. For maximum use of all this new machinery, electric lights were placed on the tractors, allowing round-the-clock operation. Other practices initiated by The Collins Farms Company included installing drainage tile, erecting fire-proof ventilated grain storage bins, and using legumes to replace nitrogen in the soil. At its peak the company operated 60,000 acres of farmland in 31 Iowa counties, with wealthy businessman M. H. Collins at the helm of the corporation. At about the age of nine, Arthur Collins became deeply interested in the new marvel of radio, although at first M. H. apparently did not think highly of his son's tinkerings with radio. Arthur and another early boyhood radio devotee, Merrill Lund, made their first crystal receivers at the Lund home at 1644 D Avenue in Cedar Rapids. The sets used variable condensers inside a tube. Merrill's father worked in the tube department at Quaker Oats Co. and made tubes of the size the boys needed. Using thumb tacks for contact points, they wrapped wire around the tubes. From iron plates they fashioned their own transformers, and rigged a 60-foot spark antenna with a lead-in through a basement window of the Lund home. Merrill's father asked them to find another location for their equipment after lightning struck the radio set and blew it up. Arthur brought over two coaster wagons and the two boys transported the damaged equipment to the Collins home at 1725 Grande Avenue. Although M. H. did not approve of the mess it was going to cause, Arthur hauled the equipment to his room once his father was out of sight. "I used a Quaker Oats box to wind the tuning coil and used a Model T spark coil," he told a New York Times reporter in 1962. "The main piece of the station's machinery was the transmitter. Other parts of the station were recruited from a rural telephone service. The way we calibrated was to pick up signals from WWV (the Navy's station in Arlington, Virginia)." Arthur also used pieces of coal or coke for a rectifier, glass towel racks for insulators and a toy motor. Those early efforts reflected a lot of experimenting that led to successively more reliable, higher-performance radios. Another boyhood friend in Cedar Rapids who also had an interest in radio was Clair Miller. "Arthur had big expensive tubes as a kid while all the rest of us had were peanut tubes," Miller told a reporter in 1965. The article quoted another neighbor's recollection of early days in the Collins family neighborhood: "We sensed that Arthur was different, but we did not know that he was a genius. When the rest of us were out playing cowboy and Indian, Arthur was in the house working on his radios." One day Arthur's mother invited the neighborhood boys into the Collins home. "I think she did so because she wanted us to realize that Arthur was different from the rest of us. We went upstairs to see what he was doing. He had a room that overlooked the yard. It was loaded with radio stuff. We knew a little about radio. We had been playing around with crystal sets ourselves. But Arthur had one wall covered with dials and switches, everything under the sun." The Federal Radio Commission, the predecessor to the Federal Communications Commission, passed a radio act whereby amateurs could get licenses. Arthur took the test and got his license in 1923 at the age of 14. As M. H. Collins recognized his son's talent and ambition toward radio, he looked for ways to help with Arthur's hobby. In about 1924, Arthur's father purchased a new tube costing $135 and other high voltage equipment. "When I was a youngster there were two real active amateurs (in Cedar Rapids)," Arthur recalled. "One was Henry Nemec and the other was Clark Chandler." Collins and Leo Hruska, another friend who had constructed a crystal receiver, used to receive the stations of Nemec and Chandler, and considered their talks with the more experienced radio operators quite an achievement. Nemec recalled how he first met the young boy with the extensive radio knowledge. M. H. Collins had asked Nemec to meet with his son so Nemec could teach Arthur some of what he knew about amateur radio, "But there wasn't much that he didn't already know," Nemec said. In a 1978 interview for an article about Henry Nemec in the Cedar Rapids Gazette, Arthur Collins recalled the early days when he purchased a vacuum tube from Nemec, and several years later when Nemec, who worked for the police department, and another patrolman, Frank Bukacek, parked their squad car in front of Collins' house while the three were inside talking radio. Collins said he, Nemec and Bukacek got together so frequently, and the squad car was parked in front of the house so often, that neighbors began to wonder whether Collins was in some kind of trouble with the police. At the time there was little formal instruction in the science of radio. Several two-day short courses were given at Iowa State College at Ames, and Arthur is said to have attended the first of these while still wearing knickers. Carl Mentzer later sponsored a course in radio at the University of Iowa. These courses, along with several periodicals, including Wireless Age and QST, comprised most of the current radio knowledge of the time, other than word- of-mouth information. By the time he was a teenager, Arthur had constructed an amateur radio station using purchased components, make-shift materials and his own ingenuity. Arthur's family had moved to a new home at 514 Fairview Drive, and his equipment moved with him. By the age of 15, Collins had communicated with other amateur "hams" in the United States and many foreign countries. The custom of exchanging postcards after a contact was made had already been established in the amateur world, and one wall of Collins' attic room was covered with so-called QSL cards. One card from Australia came from a radio operator who regarded America's prohibition of alcohol as a joke. "How does it feel to stay sober?" were the words the Australian ham wrote to 15-year-old Arthur. And during a contact with a person in Chile, the South American operator asked to be excused from the radio conversation because a volcano was erupting and interfering with the talk. "He referred to it as if it was in his backyard," Collins told a Cedar Rapids Gazette reporter in 1925. The reporter, Gladys Arne, had gone to the Collins home to talk with the 15-year-old boy because he had made a radio contact that put him on the front pages of newspapers all over the country. During the winter of 1924-25, Collins had become familiar with John Reinartz, a 31-year-old German immigrant who was prominent in radio circles because he developed a "tuner" or receiver capable of predictable selectivity and reception. Reinartz had authored several articles on the subject for radio magazines. Reinartz and Collins carried on experiments, particularly in the use of short wavelengths. Because of Reinartz's radio success, he was chosen as the radio operator for a scientific expedition to the continent of Greenland. The MacMillan expedition set sail from the coast of Maine on the ships Bowdoin and Perry in early 1925. One of the explorers was U.S. Navy Lt. Cdr. Richard E. Byrd. The plan was for the Bowdoin to make daily radio reports to the U.S. Naval radio station, but because of atmospheric problems, the land station in Washington, D.C., was unable to consistently receive Reinartz's messages. Then word spread that a 15-year-old boy in Cedar Rapid's had made contact with the expedition. Throughout the summer of 1925, Arthur Collins accomplished a task that even the U.S. Navy found difficult. Using a ham radio that he himself had built, he talked by code with Reinartz in Greenland night after night. His signals reached the expedition more clearly than any other. After each broadcast, young Collins took the messages from the expedition down to the Cedar Rapids telegraph office and relayed to Washington the scientific findings that the exploratory group had uncovered that day. Collins' exclusive contact with the expedition soon became a nationwide news story that won him acclaim as a radio wizard. The August 4, 1925 Cedar Rapids Gazette told the story: "The mysterious forces of air leaped the boundary of thousands of miles to bring Cedar Rapids in touch with the celebrated MacMillan scientific expedition at Etah, Green- land, and wrote a new chapter into the history of radio. Sunday, Arthur Collins, 514 Fairview Drive, 15-year-old radio wizard, picked up the message from the expedition's ship Bowdoin, at twenty meters (wavelength), at about 3 o'clock and conversed in continental code for more than one hour. It was the first time the expedition and any United States radio station had communicated at that wavelength. Messages were received by Collins for the National Geographic Society, which is sponsoring the expedition, and for others, and were sent out from here by telegraph. Arthur Collins is the son of Mr. and Mrs. M. H. Collins and is a student at Washington High School. He has been a radio fan for years, and has himself constructed most of his apparatus. His equipment is in a small room on the third floor of the Collins home. His station is known as 9CXX. The local boy told a Gazette reporter today that although he had been in wireless communication with Australia, Scotland, England, India, Puerto Rico, Guam, and Mexico, he never had received a greater thrill than when he talked to his friend on the famous expedition bound northward to explore a mystic continent." One week later, a follow-up article in the Gazette concluded: "Though only 15, he is true to his trust. For he hopes to realize great radio ambitions, by and by.'' At the age of 16, Collins was asked to write a technical article for Radio Age which was published in the May, 1925 issue. One statement in that article foreshadowed the motivational force which was to lead him to "great radio ambitions. "The real thrill in amateur work comes not from talking to stations in distant lands . . . but from knowing that by careful and painstaking work and by diligent and systematic study you have been able to accomplish some feat, or establish some fact that is a new step toward more perfect communication. Arthur's reputation in the radio world grew. Radio operators around the country who had heard about his contacts with the MacMillan expedition wrote to him to ask how he did it. Collins continued his electronics education by taking course.s at Amherst College in Massachusetts, Coe College in Cedar Rapids, and the University of Iowa in Iowa City. In 1927, he and two friends organized an expedition of sorts of their own. Collins, Paul Engle, and Winfield Salisbury outfitted a truck with .short wave transmitting and receiving equipment and took a summer trip to the southwest states. Using power of 10 watts they conducted experiments in connection with the U.S. Naval Observatory in Washington, D.C. Leo Hruska stayed behind in Cedar Rapids to operate the base station for the study. Like Collins, both Engle and Salisbury would later go on to achieve recognition in their particular chosen fields - Engle as a poet and professor at the University of Iowa, and Salisbury as a noted physicist who would make significant contributions to studies initiated by Collins. In 1930, Collins married Margaret Van Dyke. By the end of 1931 he had set up a shop in the basement of their home at 1620 6th Avenue S.E., previously the home of his grandparents. Arthur began to produce transmitters to order. When the depression hit with full force in 1931, 23-year-old Collins turned his hobby into a vocation. "I picked what I was interested in," he told Forbes magazine years later, "and looked for a way to make a living. " This was the first time radio transmitting apparatus, of any power output, was available for purchase as an assembled and working unit. In fact, components were hard to come by; they varied widely in characteristics, and there was little, if any, pattern to their construction. Most hams had their radio equipment scattered around a room, usually in a basement or attic where the sight of tubes and wires wouldn't clutter up living areas of a home. Their equipment was strictly functional, almost to the point of inefficiency. Collins' ham gear was designed to eliminate the clutter by packaging the equipment in neat units. The concept proved that correctly engineered construction not only stabilized the circuitry but also made its behavior predictable. Collins designed circuits, fabricated chassis, mounted and wired in components, tested, packed and shipped each unit. Because the gear was precisely engineered and well-built with the best parts available, it gave years of trouble-free service. A later article in the New York Times quoted a ham as saying, "Collins brought us up from the cellar and put us into the living room." The industrial philosophy of Collins products "quality" was established at the very start. The first advertisement for this new line of products appeared in the January, 1932 issue of QST, with the firm name given as Arthur A. Collins. Two issues later, in March, 1932, the firm name appeared as Collins Radio Transmitters with Arthur's name and call number below. Both notices were two-inch advertisements, but by May the size was increased to six inches. In October the first full-page ad appeared and by December, the firm's name was listed as Collins Radio Company . Long-time friend Jiggs Ozburn recalled his first meeting with Collins. "I first met Arthur Collins at a ham club meeting at his house (factory in basement). I hadn't finished high school and he hadn't finished college (he never did). Art had been making ham transmitters for about a year. He was tall and slender and very quiet. He came from a well-to-do family whose fortune was taking a beating in those depression years, so Art was pretty much on his own." The Great Depression, which began after the stock market crash in 1929, was having a devastating effect on the Collins Farms Company. In 1931, M. H. Collins sold the firm to an east coast insurance company. Arthur originally started his company as sole owner with only one employee, Clair Miller, who had just been graduated from Iowa State College. But as his business grew, he added personnel, including some who came from his father's farm company. Among them were John Dayhoff and Ted Saxon. Orders came in and the company grew. In 1933, Collins Radio Company moved out of the basement factory and into leased space at 2920 First Avenue in Cedar Rapids, now headquarters for the local Salvation Army. Business in general in 1933 was not good, to put it mildly, but radio had come of age, and Collins recognized the need for advancement in the radio communications field. One Saturday morning that year, Collins telephoned Arlo Goodyear and offered him a job for two months if he was willing to work on Sundays. Out of work for months and with a wife and baby, Goodyear jumped at the opportunity. "There it was in the middle of the Depression and he was asking me if I minded working on Sunday," Goodyear later wrote. "I would have worked on Shrove Tuesday." Collins and his work force of one arrived at the building only to discover that neither had a key to get into the basement area, where the company was to begin production the next morning. Collins looked at the door, looked at Goodyear, and said, "Well, we've got to get going. Catch me so I won't fall on my head." Collins charged the locked door and the new plant got underway with a bang and a shattered front door. On September 22, 1933, with eight employees and $29,000 in capital, Collins Radio Company became a corporation under the laws of the State of Delaware. At that time Delaware had some of the most modern corporation laws in the country, and many businesses were officially organizing there, although their actual facilities were located in other states. (On May 13, 1937, the company reorganized as an Iowa corporation.) _________________________________________________________________ Biography of Arthur A. Collins Reprinted from same book referenced above. Arthur A. Collins, founder of Collins Radio Company, has been called a rare man of greatness, a complex but shy person, who continually has his sights not on the epicenter, but beyond the horizon of technology. He broke barriers of conventional knowledge and made routine a pattern of scientific advancement. For him and the company he founded and directed for 40 years, work brought many personal rewards, but it was the technical breakthrough and total utilization of technology which provided the greatest motivation. Collins attended Cedar Rapids public schools, Amherst College in Amherst, Massachusetts in 1927, Coe College in Cedar Rapids for special courses, and the University of Iowa for advanced studies in physics. He received an honorary doctor of science degree from Coe College in 1954, an honorary doctorate from the Polytechnic Institute of Brooklyn in 1968, an honorary doctor of engineering degree from Southern Methodist University in 1970, and an honorary doctor of science degree from Mount Mercy College in Cedar Rapids in 1974. From 1945 through 1951, Mr. Collins served as a director of Coe College. He was a director of the Graduate Research Center of the Southwest, Dallas, from 1962 to 1969, and served on the board of directors of the Herbert Hoover Foundation . He was a member of the International Sponsors Commit-tee of the Robert Hutchings Goddard Library Program, Clark University, Worcester, Massachusetts. Mr. Collins belongs to the Institute of Electrical and Electronic Engineers, the Navy League of the United States, the American Ordnance Association, the Armed Forces Communications and Electronics Association, and was a member of the Cedar Valley Amateur Radio Club. He received the Secretary of the Navy's Distinguished Public Service Award Citation in 1 962, the Iowa Broadcasters Association Distinguished Service Award in 1966, was elected to the National Academy of Engineering in 1968, received the Armed Forces Communications and Electronics Association's David Sarnoff Award in 1979, and the Electronics Industries Association's Medal of Honor in 1980. After leaving Collins Radio in 1972, he formed a new firm, Arthur A. Collins, Inc., based in Dallas, to carry out systems engineering studies in the communications and computer fields. He was married to Mary Margaret (Meis), and was formerly married to Margaret Van Dyke, who died in 1955. He is survived by four children. _________________________________________________________________ The Popular "FA" Series Low-cost Filter A NEW FAMILY OF MECHANICAL FILTERS incorporating design and manufacturing innovations which lower prices as much as 25 percent has recently been introduced. A number of the new filters are already in production. The new developments include seven 455 kc center frequency filters with bandwidths of 500 cps, 1,500 cps, 2.1 kc, 2.7 kc, 3.1 kc, 4.0 kc and 6.0 kc. All have the steep-skirted selectivity common to all Collins mechanical filters. Packaged in a durable, high-impact phenolic case, the new filters should find wide use in commercial and amateur communications equipment, especially in single sideband transmitters and receivers. The narrow bandwidth filters are especially suited for cw and data service in receivers. Size of the new filters is 2-1/2 inches in length, and slightly more than 1/2 inch wide and 1/2 inch high, not including mounting lugs and terminals. They can be plugged into standard three-prong transistor sockets and are especially suited for circuit board manufacturing techniques involving dip soldering. A SPECIAL VERSION OF THE 455 KC FILTER with the 2.1 kc bandwidth is available for use by amateur radio operators in constructing single sideband transmitters. In these filters, the frequency reading 20 db down each side of the individual filter's selectivity curve is specified on the filter label. This aids in selection of crystals of exactly the right frequency for use in generating transmitter carrier frequency. F455 FA-21 MECHANICAL FILTER Center Frequency .....................................455 kc nom. Frequency Response Bandwidth, 6 db attenuation.......................2.1 kc nom. Bandwidth, 60 db attenuation ......................5.3 kc nom. Passband Response Variation (between 454.3 kc and 455.7 kc) ...................................... 3 db max. Transfer Impedance .........................5K ohms +/-2.25K ohms Resonating Capacity ...............................130 pf +/-5 pf Transmission Loss ........................................ 9.5 db Spurious Response Attenuation (442 kc to 468 kc) ..... 60 db min. RECOMMENDED OPERATING PARAMETERS: Signal Input Voltage: 0 to 2 volts RMS. Direct Current: Shunt feed necessary to eliminate DC current in transducer coils. DC current in transducer coils will alter filter electrical characteristics. DC Voltages: 300 VDC max. potential between coil terminals and ground. Signal Source and Load Impedance: Mechanical filters are normally used interstage. ENVIRONMENTAL REQUIREMENTS: Operating Temperature Range: -40xC to +85xC. Temperature Range, Non Operating: -65xC to +100xC. Vibration: Unit meets the performance requirements of MIL-STD- 202B, Method 201A. Shock: Filter will withstand total of 18 impact shocks of 15G's in accordance with MIL STD-202B, Method 202A. _________________________________________________________________ Mechanical Filter Theory PACKAGED IN CASES AS SMALL as one-third cubic inch, Collins Mechanical Filters achieve a flat-topped frequency response characteristic; they have been built with a 60 to 6 db shape factor as low as 1.2 to 1. Among all types of filters, only Collins Mechanical Filters provide this steep-skirted selectivity approaching the theoretically-perfect. This selectivity comes from a series of resonant dime-size nickel-alloy discs with Q's of 8,000 to 12,000, up to 150 times more than conventional filter elements. Mechanical Filters are electrically and mechanically stable and they resist aging, breakdown and drift even with extreme temperature changes or long, continuous service. For example, frequency shift of a typical Mechanical Filter holds between 1.5 and 2 parts per million/degree C over a -25xC to +85xC range. (The Filters will operate over a range exceeding 55C to +105xC.) MECHANICAL FILTERS RESIST AGING to a remarkable degree. In a recently completed accelerated aging test, a number of standard filters were steadily cycled between 25xC and 90xC for an eight-month period. Maximum deviation exhibited by any filter during this period was less than one part per million. To the equipment design engineer, these factors mean an increase in performance and reliability and decrease in size, expense and maladjustment; for these reasons the Mechanical Filter has been widely accepted by industry and the Armed Forces. MECHANICAL FILTER DESIGN is based on well established principles. The Filter is a mechanically resonant device which receives electrical energy, converts it into mechanical vibration, filters out unwanted frequencies, then converts the mechanical vibration back into electrical energy at the output. THE MECHANICAL FILTERS consist of three basic elements: (1) transducers which convert electrical oscillations into mechanical oscillations or vice versa, (2) mechanically resonant metal discs, and (3) disc coupling rods. THE TRANSDUCER, which converts electrical and mechanical energy, is a magnetostrictive device based on the principle that certain materials elongate or shorten when in the presence of a magnetic field. When an electrical signal is sent through a coil which contains the magnetostrictive material as the core, the electrical oscillation will be converted into a mechanical oscillation. The mechanical oscillation can then be used to drive the mechanical elements of the Filter. In addition to electrical and mechanical conversion, the transducer also provides proper termination for the mechanical network. FROM THE ELECTRICAL ANALOGY circuit shown on page 3, it is seen that the center frequency of the Mechanical Filter is determined by the metal discs, which are represented by the parallel resonant circuits. (Filters with center frequencies between 60 kc and 600 kc are being manufactured. This by no means indicates limitations, but is merely the area of current design concentration. See above graph.) Since each disc represents a parallel resonant circuit, increasing the number of discs increases skirt selectivity of the Filter. Skirt selectivity is specified as shape factor, which is the ratio (bandwidth 60 db below peak) / (bandwidth 6 db below peak). IN THE EQUIVALENT CIRCUIT, the coupling inductors represent the rods which couple the discs. By varying the mechanical coupling between the discs, i.e., making the coupling rods larger or smaller, the bandwidth of the Filter is varied. Because the bandwidth varies approximately as the total area of the coupling wires, the bandwidth can be increased by either using larger or more coupling rods. Standard available bandwidths range from 500 cps to 50 kc, and special units have been built with bandwidths as narrow as 300 cps and as wide as 60 kc. CURRENT IMPROVEMENTS. Considerable progress is being made in improving selectivity and other performance characteristics of mechanical filters. The use of ferrite transducer elements, for example, has reduced insertion loss and passband ripple while making practical the cascading of various filter types as a means of improving selectivity. Magnetostrictive ferrites used in transducers have also made possible greater fractional bandwidths and reduction in microphonic responses. Careful grading and heat treatment of the nickel-alloy disc resonant elements has resulted in temperature coefficients of the discs being reduced to as low as one part in one million per degree Centigrade over a 100-degree range. Other means of increasing selectivity in general and of producing more effective filters for single sideband application are being investigated. These include cascading two filters together and intentional distortion of the nodal pattern of the discs. APPLICATIONS FOR THE WIDE RANGE of standard Filters include high performance transmitting and receiving equipment, multiplexing equipment, missile guidance systems, frequency synthesizers, Doppler radar, data transmission systems, precision navigation equipment and spectrum analyzers. Many advances in frequency spectrum conservation have been made possible by Mechanical Filters and their superior selectivity characteristics. Such techniques are split- channel reception, improved methods of amplitude modulation and single sideband communication and superior detection methods for data transmission systems. THE DESIGN OF CIRCUITS employing Mechanical Filters is relatively simple, since no special matching networks are normal]y required. Being internally terminated, the filters need only a high-resistance termination (50,000 ohms or greater) at either end together with the capacity (approximately 130 pf) required to resonate filter input and output at the center frequency. THIS HIGH RESISTANCE is readily obtained by driving the Filter with a pentode tube (effectively a constant current generator) and terminating it into a vacuum tube grid. It was this usage that led to the use of the term "transfer impedance" in specifying the effect of a Mechanical Filter on the gain of a given circuit. The transfer impedance is the ratio of the input current to the output voltage, so the over-all gain of an amplifier stage with a Mechanical Filter following the amplifier tube is simply equal to the transconductance of the tube times the transfer impedance. THE SMALL SIZE and high performance characteristics of Mechanical Filters make them a natural choice when designing bandpass circuits using transistor amplifiers. The filters can be readily matched into the low-resistance circuits (1,000 ohms or less) encountered with transistors by using a series resonant termination. The lowest value of impedance that can be matched is determined by the extent to which the stray capacity across the Filter can be minimized. This impedance will be in the order of magnitude normally encountered with grounded emitter amplifiers. In some applications, such as balanced modulators, it is desirable to terminate the Filter into a balanced load. For this reason, each set of terminals on the Filter is balanced to ground, eliminating the need for isolation transformers or amplifiers in circuits of this type. WHEN MECHANICAL FILTERS ARE USED IN BANDPASS circuits there are a number of precautions that must be taken if full advantage is to be derived from its steep skirt rejection capabilities: For example, the use of short wires between the Filter terminals and the termination circuitry; effective shielding between the input and the output, and the use of a common ground for the Filter input, shield and output. These precautions prevent the input signal from partially bypassing the Filter through inductive or capacitive coupling or ground loops. SINGLE SIDEBAND APPLICATIONS. Collins Mechanical Filters have found great acceptance in single sideband transmitter and receiver applications because they provide the flat- topped passband and steep selectivity needed to reject the unwanted sideband and closely adjacent channels in the receiver. Filters will meet general performance requirements over the temperature range of -40xC to +85xC with the following maximum allowable deviation limits from the specified +25xC requirements: Center Frequency 10 ppm/xC (normally 2 to 5 ppm/xC) Bandwidth +/- 5% Peak-to-Valley Ratio 1 db increase Transfer Impedance +/- 10% Filters can be stored at temperatures from -65xC to +100xC without detrimental effects. _________________________________________________________________ Filter Case Types... [IMAGE] _________________________________________________________________ Mechanical Filter Finder 6 db Max 60 db Center Freq. Type# No. Part No. Bandwidth Bandwidth Case Style 250 kc F250A-20 526-9012- 00 2.0 kc 4.3 kc C 250 kc F250A-67 526-9039- 00 6.7 kc 14.0 kc C 250 kc F250A-85 526-9049- 00 8.5 kc 18.0 kc C 455 kc 455E-05 526-9321- 00 0.5 kc 2.5 kc E 455 kc F455F-05 526-9318- 00 0.5 kc 2.5 kc F * 455 kc F455FA-05 526-9494- 00 0.5 kc 2.5 kc FA 455 kc F455H-05 526-9229- 00 0.5 kc 2.5 kc H * 455 kc F455J-05 526-9154- 00 0.5 kc 2.5 kc J 455 kc F455K-05 526-9228- 00 0.5 kc 2.5 kc K 455 kc F455E-15 526-9370- 00 1.5 kc 3.5 kc E 455 kc F455F-15 526-9227- 00 1.5 kc 3.5 kc F * 455 kc F455FA-15 526-9495- 00 1.5 kc 3.5 kc FA 455 kc F455H-15 526-9170- 00 1.5 kc 3.5 kc H * 455 kc F455J-15 526-9155- 00 1.5 kc 3.5 kc J 455 kc F455K-15 526-9168- 00 1.5 kc 3.5 kc K 455 kc F455E-21 526-9322- 00 2.1 kc 5.3 kc E 455 kc F455F-21 526-9323- 00 2.1 kc 5.3 kc F * 455 kc F455FA-21 526-9427- 00 2.1 kc 5.3 kc FA 455 kc F455H-21 526-9313- 00 2.1 kc 5.3 kc H * 455 kc F455J-21 526-9156- 00 2.1 kc 5.3 kc J 455 kc F455K-21 526-9317- 00 2.1 kc 5.3 kc K * 455 kc F455Y-21 526-9337- 00 2.1 kc 5.3 kc Y 455 kc F455E-31 526-9074- 00 3.1 kc 6.5 kc E 455 kc F455F-31 526-9075- 00 3.1 kc 6.5 kc F * 455 kc F455FA-31 526-9496- 00 3.1 kc 6.5 kc FA 455 kc F455H-31 526-9093- 00 3.1 kc 6.5 kc H * 455 kc F455J-31 526-9089- 00 3.1 kc 6.5 kc J 455 kc F455K-31 526-9169- 00 3.1 kc 6.5 kc K * 455 kc F455Y-31 526-9338- 00 3.1 kc 6.5 kc Y 455 kc F455E-40 526-9324- 00 4.0 kc 8.5 kc E 455 kc F455F-40 526-9325- 00 4.0 kc 8.5 kc F * 455 kc F455FA-40 526-9497- 00 4.0 kc 8.5 kc FA 455 kc F455H-40 526-9326- 00 4.0 kc 8.5 kc H 455 kc F455J-40 526-9327- 00 4.0 kc 8.5 kc J 455 kc F455K-40 526-9303- 00 4.0 kc 8.5 kc K * 455 kc F455Y-40 526-9339- 00 4.0 kc 8.5 kc 455 kc F455E-60 526-9084- 00 6.0 kc 12.6 kc E 455 kc F455F-60 526-9087- 00 6.0 kc 12.6 kc F * 455 kc F455FA-60 526-9498- 00 6.0 kc 12.6 kc FA 455 kc F455H-60 526-9094- 00 6.0 kc 12.6 kc H * 455 kc F455J-60 526-9091- 00 6.0 kc 12.6 kc J 455 kc F455K-60 526-91S9- 00 6.0 kc 12.6 kc K * 455 kc F455Y-60 526-9340- 00 6.0 kc 12.6 kc Y 455 kc F455E-80 526-9332 00 8.0 kc 18.5 kc E 455 kc F455F-80 526-9331- 00 8.0 kc 18.5 kc F 455 kc F455H-80 526-9330- 00 8.0 kc 18.5 kc H 455 kc F455J-80 526-9329- 00 8.0 kc 18.5 kc J 4SS kc F455K-80 526-9328- 00 8.0 kc 18.5 kc K 455 kc F455Y-80 526-9341- 00 8.0 kc 18.5 kc Y 455 kc F455E-120 526-9336- 00 12.0 kc 23.0 kc E 455 kc F455F-120 526-9173- 00 12.0 kc 23.0 kc F 455 kc F455H-120 526-9171- 00 12.0 kc 23.0 kc JH 455 kc F455K-120 526-9316- 00 12.0 kc 23.0 kc K 455 kc F455Y-120 526-9342- 00 12.0 kc 23.0 kc Y 455 kc F455E-160 526-9320- 00 16.0 kc 27.5 kc E 455 kc F455F-160 526-9335- 00 16.0 kc 27.5 kc F 455 kc F455H-160 526-9314- 00 16.0 kc 27.5 kc H 455 kc F455K-160 526-9315- 00 16.0 kc 27.5 kc J 455 kc F455Y-160 526-9343- 00 16.0 kc 27.5 kc Y 500 kc F500B-08 526-9007- 00 0.8 kc 3.5 kc E 500 kc F500B-14 526-9030- 00 1.4 kc 3.8 kc E 500 kc F500B-31 526-9008- 00 3.1 kc 3 5 kc F 500 kc F500Y-31 526-9426- 00 3.1 kc 8.0 kc Y 500 kc F500B-60 526-9009- 00 6.0 kc 14.0 kc E 500 kc F500F-60 526-9319- 00 6.0 kc 19.0 kc F 500 kc F500Y-60 526-9378- 100 6.0 kc 13.2 kc Y 64 kc F64Z-7 526-9396- 00 Lower Sideband L 68 kc F68Z-7 526-9397- 00 " " L 72 kc F72Z-7 526-9398- 00 " " L 76 kc F76Z-7 526-9399- 00 " " L 80 kc F80Z-7 526-9400- 00 " " L 84 kc F84Z-7 526-9401- 00 " " L 88 kc F88Z-7 526-9402- 00 " " L 92 kc F92Z-7 526-9403- 00 " " L 96 kc F96Z-7 526-9404- 00 " " L 100 kc F100Z-7 526-9405- 00 " " L 104 kc F104Z-7 526-9406- 00 " " L 109 kc F108Z-7 526-9407- 00 " " L 250 kc F250Z-4 526-9130- 00 Upper Sideband C 250 kc F250Z-5 526-9131- 00 " " C 455 kc F455Z-4 526-9354- 00 Upper Sideband Y 455 kc F455Z-5 526-9365- 00 Lower Sideband Y 455 kc F500Z-4 526-9377- 00 Upper Sideband Y 455 kc F500Z-5 526-9376- 00 Lower Sideband Y * Used in Collins Amateur Products _________________________________________________________________ TUBE COMPLEMENT FOR COLLINS RADIOS _________________________________________________________________ [IMAGE] _________________________________________________________________ Tube listings by radio in alphabetical order... Model Qty Tube Description 136B-2 4 6U8 Noise Blanker 30L-1 4 811A Linear Amplifier 30S-1 1 12AL5 Linear Amplifier 30S-1 2 3B28 30S-1 1 4CX1000A 312B-5 1 6AU6 Remote VFO 32S-3/A 3 12AT7 Transmitter 32S-3/A 2 6146B 32S-3/A 1 6AH6 32S-3/A 1 6AL5 32S-3/A 2 6BC6 32S-3/A 1 6CL6 32S-3/A 3 6U8 32S-3/A 1 OA2 516F-1 1 5R4 Power Supply 516F-1 1 5U4 516F-2 1 5R4 Power Supply 516F-2 1 5U4 51S-1 2 12AX7 Receiver 51S-1 1 5670 51S-1 1 6AK6 51S-1 1 6AU6 51S-1 5 6BA6 51S-1 1 6BF5 51S-1 1 6DC6 51S-1 5 6EA8 62S-1 1 12AT7 VHF Transverter 62S-1 1 4X150A 62S-1 1 6BZ6 62S-1 1 6EA8 62S-1 4 6ER5 62S-1 2 7558 75A-4 2 12AT7 Receiver 75A-4 1 12AU7 75A-4 1 12AX7 75A-4 1 5Y3GT 75A-4 4 6AL5 75A-4 1 6AQ5 75A-4 8 6BA6 75A-4 2 6BA7 75A-4 1 6DC6 75A-4 1 OA2 75S-3/C 1 12AX7 Receiver 75S-3/C 1 6AT6 75S-3/C 1 6AU6 75S-3/C 2 6BA6 75S-3/C 1 6BF5 75S-3/C 3 6DC6 75S-3/C 3 6EA8 KWM-1 2 12AT7 Transceiver KWM-1 1 12AU7 KWM-1 1 12AX7 KWM-1 2 6146B KWM-1 1 6AH6 KWM-1 3 6AL5 KWM-1 1 6AQ5 KWM-1 1 6AU6 KWM-1 4 6BA6 KWM-1 3 6BA7 KWM-1 1 6CL6 KWM-1 2 6DC6 KWM-1 6 6U8 KWM-2/A 2 12AT7 Transceiver KWM-2/A 2 6146B KWM-2/A 1 6AU6 KWM-2/A 3 6AZ8 KWM-2/A 3 6BN8 KWM-2/A 1 6CL6 KWM-2/A 1 6DC6 KWM-2/A 1 6EA8 KWM-2/A 4 6U8 KWS-1 6 12AT7 Transmitter (RF Deck) KWS-1 1 3TF4A KWS-1 2 4X150A KWS-1 1 5749 KWS-1 1 6AL5 KWS-1 1 6AU6 KWS-1 4 6BA6 KWS-1 2 6CL6 KWS-1 1 6X4 KWS-1 2 OB2 KWS-1 PS 1 12AX7 Transmitter (Power Supply) KWS-1 PS 1 2D21 KWS-1 PS 2 3B28 KWS-1 PS 1 5U4 KWS-1 PS 1 5Y3GT KWS-1 PS 1 6AL5 KWS-1 PS 1 6AS7 KWS-1 PS 1 OB2 R-390A 1 0A2 Receiver R-390A 1 3TF4A R-390A 7 5814 R-390A 2 6AK5 R-390A 3 6AK6 R-390A 6 6BA6 R-390A 3 6C4 R-390A 1 6DC6 _________________________________________________________________