MARCONI RECEIVERS & TRANSMITTERS -------------------------------- Maintained by Jerry Proc VE3FAB Release date: July 23, 1995 File name: MAREQLST The purpose of this document is to provide a description of tube equipment produced by Marconi. This list is restricted to communications receivers/transmitters and radio direction finding apparatus (excluding radar) employing vacuum tubes. Any input that will help to enhance the contents of this list is most welcome. Please send your contribution to: jproc@worldlinx.com Ensure that text is left justified and is composed just like the text below. I will edit if necessary and post updated versions of this list to the BA archives as required. All contributors will receive credit within this file. I will also accept equipment descriptions for radar and other Marconi tube equipment and I will publish and maintain an additional Marconi equipment list if there is sufficient interest. MARCONI EQUIPMENT LIST ---------------------- B28 Receiver ------------ This was a dual range superheterodyne receiver which was developed from the Marconi CR100/4 series of receivers of 1940. The low frequency band coverage was 60 to 420 kcs while medium/high frequency coverage was 500 kcs to 30 mcs. Power input - 200/250 VAC, 50 Hz @ 85 watts or batteries. Weight - 82 pounds. Dimensions - 16 x 16.5 x 12.5 inches B29 Receiver ------------ Originally developed from the Marconi CR200 receiver in 1941, this unit was a five tube TRF (tuned radio frequency) design and had a frequency range of 15 to 550 kcs. The B29 incorporated two VR100 RF amplifiers, a VR99 detector/oscillator, two AF stages (6J5 and NR69) and a 5U4G rectifier tube. A narrow, 1 kcs bandwidth filter was included in the audio stages for CW reception. It could operate on 120/220 VAC 50 Hz or 6VDC power sources. Power input - 100/110 or 200/220 VAC, 50 Hz @ 33 watts. Weight - 82 pounds. Dimensions - 19 x 13.5 x 16 inches. CR100/2 ------- Frequency range: 60 to 420 khz in two bands 500 khz to 30 Mhz in four bands. DC supplies : Fil 6V @ 4 amps; 250v @ 100 ma for HT Mains supply : 200-250 V 50 Hz; 85 Watts Inputs : 100 ohm feeder, balanced or unbalanced. Sensitivity : 20 db s/n ratio on CW in 3Khz bandwidth 60 khz - 11 Mhz: 1 to 2 microvolts 11-30 Mhz : 1.5 to 4 microvolts Outputs : Speaker - 3 ohm, 2 watts max. Line - 600 ohm, about 2 mw. Editions : CR100 to CR100/8 including Navy B28 Dimensions : 16" x 16.5" x 12.5" Weight : 82 lbs. Handbook : T1868/1 CR100/4 - See B28 ----------------- CR150/3 ------- Frequency range: 2 to 60 Mhz in five bands DC supplies : Fil 6.3 v @ 3.7 amps; 300 V @ 65 ma for HT Mains supply : Separate unit - 200-250 VAC, 50 Hz consumes 90 watts. Inputs : 75 to 100 ohm balanced or unbalanced Sensitivity : 20 db s/n ratio on CW in 8 khz bandwidth 2 - 16 Mhz; 1 to 2 microvolts 16 - 32 Mhz; 2 to 4 microvolts 32 - 60 Mhz; 7 to 14 microvolts Outputs : 1 mw to HR or LR headphones 200 mw to 600 ohm line or 3 ohm loudspeaker Editions : CR150 to CR150/6 Dimensions : 20.5" x 17" x 14" Weight : 62 lbs - receiver only Handbook : T2148/1 CR200 - See B29 ----------------- CR300 ----- Frequency range: 15 Khz to 25 Mhz in eight bands DC supplies : Fil - 24V @ 0.95 amps; 250 V @60 ma for HT Mains supply : Depending on power supply used - 230 V 50 Hz; 24 VDC, 110 or 220 VDC Inputs : Single wire aerial not exceeding 700 pF Sensitivity : 20 db s/n ratio on CW 85 khz - 25 Mhz; 2 to 5 microvolts 15 Khz - 85 Khz; 35 to 70 microvolts Outputs : 2 watts to 3.5 ohm loudspeaker 10 mw to 60 ohm headphones Editions : CR300/1 with 500 khz crystal calibrator CR300/2 with 690 Khz crystal calibrator Dimensions : 18.75" x 15.5" x 13.625" Weight : 55 lbs. FH3 HF/DF Receiver ------------------ This unit was a primitive D/F device which relied on operators manually scanning suspected frequencies. Detection was provided by an audio signal heard in a headphone. Direction finding was accomplished by turning the antenna to where the signal was the strongest. Distance was impossible to determine accurately, but operators soon learned to distinguish HF ground waves from sky waves. Since ground waves could only be detected 12 to 14 miles from the transmitter, FH3 operators knew when an intercepted signal represented a close target. The FH3 incorporated the B21B receiver which had a frequency coverage from 1 to 20 mcs. It was connected to a fixed aerial system consisting of two crossed, screened loops (Bellini-Fosi system) for direction finding and a vertical aerial for sense detection. For testing the performance of the apparatus, Frame Coil S25B was used. This is an arrangement in which a signal was injected into the unit and would simulate a bearing at GREEN 45o. Circa - early 1940's. FH4 HF/DF Receiver ------------------ A high frequency (1 to 24 mcs) HF/DF receiver which had a cathode ray scope for direct visual bearing indication and was superior to its predecessor due to the ability of being able to distinguish between the sky wave and the ground wave. Its scope was as big as a pie plate, and was surrounded by a compass rose. Accuracy was limited from 2 to 10 degrees and the unit operated on a 230 VAC 50 Hz mains source. The FH4 was connected to a Bellini-Fosi aerial array consisting of fore/aft (F/A), port/starboard (P/S) loops and a sense aerial. Circa - early 1940's. FM12 Huff Duff Receiver ----------------------- This was a tuned radio frequency (TRF), direction finding receiver with an frequency range of 42 to 1060 kcs and required 220VAC input power. A directional loop antenna mounted was connected to the receiver inputs via dual connector blocks and RG57 coax. In addition, an gyro repeater was required to provide reference bearings for the operator. The FM12 was a very good direction finding set for its day. In taking a bearing, the use of the multi-purpose switch was very important. An operator would first tune in the signal of the target station with the Aerial switch in the search position. Then, with the switch in loops, a minimum strength on the outside compass scale of the goniometer was found. Lastly, the operator would place the Aerial switch in the sense position and would rotate the goniometer slowly clockwise. If the signal faded away, the minimum position was the true bearing. Had the signal risen, it indicated a reciprocal bearing and true bearing would be found 180 degrees on the opposite side of the scale. FR12 Transceiver ---------------- Made by Canadian Marconi in 1944, the FR12 was a three mode transceiver - CW, MCW and radio telephone. Power input was 15 watts on CW, less on MCW and even less on phone. It was capable of transmitting on low wave (375 to 580 kcs) or short wave (1700 to 4200 kcs) depending on the model type. On low wave, the set had a range of about 20 miles. On receive, it was capable of continuous tuning from 300 to 4200 kcs. The letter H (ie FR12-TH) in the model number indicates that the remote control option was installed. The receiver section consisted of a five tube superheterodyne design with the ability to continuously tune the range of 300 to 4200 kcs in three bands. To simplify the overall design, there is no direct frequency readout for the receiver. Instead, a circular logging scale dial was provided. It is necessary to calibrate the dial and record the readings in advance. In the transmitter section, there was an oscillator, a modulator and a dual power output stage. One of four, selectable, internally mounted crystals determined the operating frequency. In order to activate the modulator, one simply inserted the handset plug into the front panel socket. The microphone in the handset provided the interlock for the modulator. Power for the FR12 could be provided by one of two modes. In standby mode, the filament circuit for the transmitting tubes was disabled. Filament power for the receiver would be provided from the main battery. The 180 volt B+ line for the receiver would be furnished from four, external, 45 volt dry batteries wired in series. Standby mode would dramatically increase the life of the main battery. In normal mode, all power for the receiver and transmitter was provided by the main battery. An internal Dynamotor produced high tension for the transmitter but it had to be inspected after every 500 hours of operation. Input power to the FR12 was 12 volts DC at 6 amps on receive and 13 amps on transmit when used in normal mode. MDF5 - Can anyone confirm that this was a Marconi D/F receiver? ---- MSL5 Receiver ------------- Made in the early 1940's, this was a four tube, low/medium frequency regenerative receiver, operating in the 15 to 1550 or 15 to 1775 kcs band depending on the variant. This receiver required an external battery supply (90 VDC plus 6 VDC) which was connected to chassis mounted binding posts. Since there was no audio output stage, earphones were required for normal operation. Stations were tuned in by operating two separate tuning controls and two non-ganged range switches. For CW reception, a 1440 Hz note filter was used. One unique feature in this design, was a self-contained crystal radio. If the MSL5, or its power source failed, the operator would move the antenna from the binding post marked VAL (valve) to the binding post called CRYS (crystal). Crystal headphones would have to be plugged into a separate front panel jack. An easily accessible, internally mounted, cat whisker crystal would then be manipulated until the most sensitive spot was found, exactly the way it was done with early crystal radio sets. In later MSL5 models, the cat whisker crystal was replaced with a crystal diode such as the 1N34. In crystal radio mode, stations were tuned by operating the antenna tune control in conjunction with the band switch mounted directly above it. CM11 Transmitter/Receiver ------------------------- First built in 1942, the CM11 was a transmitter/receiver that was capable of operation in the 375 kcs to 13.5 mcs range. There were two distinct bands of operation: 375 to 515 kcs on low frequency and 1.5 to 13.5 mcs on high frequency. In the high frequency band, the CM11 could be used with crystal or master oscillator frequency control. For low band operation, only the master oscillator could be used. Modes and power levels were: CW - 100 watts; MCW - 70 watts; AM - 30 watts. The internal antenna tuner was a very versatile device, since it could match antennas that were 5 to 750 ohms resistive and supported operation in the range of 375 kcs to 13.8 mcs. The CM11 was notorious for generating harmonics and spurious emissions. The CM11 was also known for its chirpy CW signal when controlled by the master oscillator but it behaved properly under crystal control. The power supply for the CM11 was very flexible as it could operate on 120/220 VAC or 24/36/220 VDC power sources. A fifteen second time delay circuit prevented power from being applied to the transmitter in order to protect the mercury vapour rectifiers. There was an emergency mode which decreased the time delay to 4 seconds but at the expense of shorter mercury rectifier life. Weighing in around 478 pounds, the CM11 just wasn't portable! CSR 5A Receiver --------------- First built in 1942, this general coverage receiver was capable of receiving AM and CW signals between 80 kcs and 30 mcs with the exception of the broadcast band. It had a tube count of thirteen and weighed in at sixty eight pounds without power supply. Each receiver was connected to its own external speaker. A modification was made to this receiver by the Royal Canadian Navy during the 1950's and 1960's. The "F" band (80 to 200 kcs) was adjusted 10 kcs low to enable the reception of the broadcast frequency of 73.6 kcs. The VP3 power supply for the CSR 5A was designed to operate from 120/220 volt 50/60 Hz AC power or 12 VDC. When operating on DC power, some changes had to be made. Marconi designed two power interlocks to ensure that no damage could be caused by inadvertent operation on the wrong power source. To switch from AC to DC operation, a five pin interlock plug had to be moved from one socket to another. Subsequently, the AC line cord had to be disconnected from the wall socket and inserted into a special chassis mounted receptacle. VP3 power supplies also acquired a reputation for fusing the contacts on the vibrator and frying the primary winding on the power transformer. When CSR 5A receivers were rack mounted, they were usually powered with a Marconi WE11 rack mounted power supply. This supply only operated from a 120 or 220 VAC power source. PV500 Transmitter and Variants ------------------------------ The PV500 HM was first built in 1943 and it was a high powered, CW only transmitter, capable of operating in the range between 3 to 19 Mcs. Power input was 500 watts over this frequency range. There were four, switch selectable, master oscillators that could be preset to the most often used frequencies. Alternately, four crystal controlled frequencies were also available. The HM2 variant of the PV500 operated up to 28 Mcs, however, power input was reduced to 300 watts above 19 Mcs. Since there was no drive level control on the HM2, there was excessive drive at lower frequencies and insufficient drive at high frequencies. Multiplier stages had to be detuned to obtain the desired drive levels. To reduce chirp on CW, the multiplier stages were keyed while the oscillator was held on for the duration of a 'word'. This reduced chirp to the first letter of each word sent and permitted the use of break-in operation. In the PV500 HM3, there were design changes to overcome deficiencies of the previous models. A driver stage and drive level control were added. Frequency shift control capability was added. In the previous models, there was a large power loss in the trunking to the antenna, so the antenna tuner was removed from the transmitter and was re-designed for remote operation. Voltage requirements for the PV500 were as follows: DC AC B+ (high) 2700 volts Mains : 120 VAC @ 20 amps B+ (low) 600 volts Screen supply 375 volts Bias -225 volts PV500 LM Transmitter ------------------- The PV500 LM transmitter was a CW only unit operating in the frequency range of 100 to 500 kcs. It had a rated power input of 500 watts and frequency control was by master oscillator (M.O) only. There were four switch selectable M.O's in total and they were pre-set to the four most popular operating frequencies. TV5 Transmitter/Receiver ------------------------ The Marconi TV5 emergency transmitter/receiver was generally located in a ship's main radio office and was remotely operated by Morse key or voice. Freq Range (TX) : 1200 to 3000 kcs; plus 500 kcs (RX) : 400 to 1200 kcs; 1200 to 3300 kcs Average power input : 15 watts Modes : CW/MCW/VOICE Power input : 24 VDC Circa : mid 1940's