1.0 DRAKE MODS (10 NOV, 1995) ______________________________ This document is considered public domain and you are free to distribute this document in its entirety without alteration. No fees or payment is to be granted or collected in the distribution of this material. While reasonable effort has been made to ensure accuracy of data, the author assumes no liability or responsibility for the consequences of any action on the part of any reader through the use of this information. Enclosed are a number of mods available for various pieces of Drake equipment of the 4 series and later. Some of these changes I have per- sonally implemented and some are collections from other sources. What I've tried to do here is not only list the mods that I know of, but to share some of my experiences with the equipment. I've included some historical information and some thoughts on what the B and C series are about. A large part of the reason for this is that I've had to find this out myself - the hard way. A lot of the data is what I would of liked to have known before I started to acquire some of this gear. What surprised me most about this equipment is that there is almost no data external from Drake available. No mods - and I searched every where. No knowledge of what makes a particular example a good one. I was on my own, and try- ing to not just render my gear serviceable, but restore it also. Just what do you do with a mechanically unstable PTO? Is it possible to fix it? What is the ALC behavior of a properly operating TR7? And so on. With but one or two minor exceptions, every unit listed I have had some experience with, but not all of the mods have been deployed. Mods obvi- ously have been found. Some of them are from my having bought my latest flea market 'works great - just aligned' joy home, cracked the covers and WHOOOOOOA! Whats *this*? (ever seen someones attempt at turning a Heath HR20 into a base for a radio telescope? don't ask). You'll find this document a little different than most 'mod strings'. The reason for this is that if you screw up (say) a Kenwood mod, you just put the mess in a box, take it to a dealer and throw some money at him. Well, I'm sure you've noticed that Drake dealers are in short sup- ply these days. AND surprise surprise - while a lot of technicians might be able to service a multi loop PLL synthesiser, they have never seen a 12AX7 or have a clue just how a glassFET works. As a general rule, modifications are to be AVOIDED unless there is a specific problem to be addressed or a requirement to be added. I strongly recommend that you do not make any equipment changes unless there is a good reason to do so. The only reason to modify a piece of well engineered equipment is to fix an oversight or add a capability that currently does not exist. You should never modify equipment unless it is working as well as it could. Modifying equipment that is not work- ing properly will only make it work .... worse. Drake Mods (10 Nov, 1995) 1 1.1 GENERAL ____________ Comments in this section are generally common to all Drake 4 line equip- ment. - PTO End Play If the tuning knob can be wiggled from side to side, chances are the end play needs adjustment. End play can be adjusted by tightning the ball bearing on the PTO tuning worm gear. Some Drake equipment might have extra hole on the PTO cover for this purpose. For those that do not, you must remove the PTO cover and use a long 1/8" allen (hex) wrench. The adjustment 'nut' in question is recessed beneath the coil form. Do not over- tighten or you will ruin the dial drive ball bearings and race. Do not disturb any placement of components or you will affect the PTO dial tracking. - PTO General Notes Most of the PTO units are much the same throughout the 4 line, but the drive mechanisms and indicator plates are not. The worst things you can do to a Drake PTO is to continue tuning past the STOP indi- cation or clean the dial plates with something that disolves the plastic. Be very carefull with cleaner on those Lexan dial plates! If in doubt, use mild soap and warm water. Dial plate replacement is impossible (there are no 'C' line dial plates to be had). Drake will service the PTO for you - they have the gears and other mechanical parts and can reset the PTO for drift and linearity spec. It would be most wise, however, to not lunch the PTO gears and dial plate. - PTO Evolution The PTO stayed basically the same over the years. It is a good, solid design. Early model PTO assemblies had a brass pin that was driven into a slot in the gear to provide a stop. As these assem- blies wore, sometimes the pin would not extract itself and the PTO drive would end up in a locked state. If this was forced, the pin will snap, leaving no dial stop at all and the dial plate will go around and around until the slug bottoms. Later assemblies used nylon gears and dual dial plates on a concen- tric shaft. Some of these dial plates are 3 pin and some are 2 pin. The number of pins refers to the brass rivets that hold the dial plates to the gear faces. There is no stop to speak of in these assemblies and turning past the mechanical resistance of the drive assembly will lunch the gears. These PTO drive assemblies may have 'ears' and there may be 2 ears just behind the gear assemblies. The purpose of these ears is to allow the dial plates to be rotated for proper mechanical orientation with the dial window gradical. - PTO Mechanical Instability Drake Mods (10 Nov, 1995) 2 This is usually caused by either the worm gear tension spring not hooked to the aluminium PTO cover or by the end cap on the end of the PTO coil form being loose. If the problem is not the tension spring, remove the PTO cover and look at the end of the PTO coil form. You will see a cap on the end of it. It should not be loose. If it is loose, carefully remove it, apply some glue and stick it back on. The coil form is delicate! The end cap just has a square hole through which the tuning slug brass rod goes through. For glue, I use GOOP. See also PTO End Play above. - PTO Lubrication Given the age of these unit, the grease is starting to dry out. Its possible that it may even has run away slightly after seeing God knows what use in a car or in a hot tent on Field Day many years ago. Most important is to lubricate that worm gear. I use Teflon spray lube. Just use the slightest bit. Too much is much worse than too little. The dial mech should offer only slight resistance to the tuning knob. You should be able to fast spin the tuning knob by placing your index finger on the outside of the knob and rotating your hand. If you cannot do this, then you have some kind of a prob- lem in the PTO dial mech. - PTO Skipping/Hysteresis Inability to have the C line dial plates to indicate exactly the same frequency after moving away 100 KHz or so and returning to the same frequency is usually caused by the rubber collar under tuning knob and dish. After all these years, the rubber has hardened or has worn. Replace the PTO rubber. The C clip should not be tight against the aluminum washer and the washer should be installed such that the groove around the perimeter is facing outside. - Dial Plates These are NOT available from Drake for the C line any more. Use cleaning materials with extreme caution. - Dial Plate Scraping The dial plates are fairly large diameter Lexan disks. On the C line, there are 2 of them. One knob turn tunes the receiver 25 KHz. Sometimes the dial plates will scrape as they are rotated usually somewhere around the front panel. Over the years, some heat warping should be expected. Quite often though the scraping is caused by poor assembly after removing the front panel for cleaning. If the whole PTO had been removed, there is a little positioning adjustment available if the 3-4/40 nuts are loosened. Ensure the dial gradical plastic is on the outside of the sub chas- sis with the red line on the inside of the window (C line). Drake Mods (10 Nov, 1995) 3 On all radios, the blue filter mounts on the back of the white plas- tic dial backing. Make sure the dial light wires are positioned away from the dial plates. - Sensitivity Check - all Drake 4 line All Drake receivers and transceiver should provide a noise peak as the preselector is passed across the tuning range, even on 10 me- ters. If your equipment does this with no antenna connected, you have all the sensitivity you can use. If it fails to provide a peak, alignment is immediately suspect. Generally, the calibrator should provide an S9 meter reading on 10 meters, progressively increasing as the band switch is rotated to 80 meters. - Front Panel The 4 line has spacers in the 4 corners of the front panel. Be carefull when you remove the front panel. The thickness of the spacers seems to be 1/16" or so and they are, of course, black. They disappear as soon as they hit the ground. - Screws and fittings There are no metric fittings that I know of. Most of the machine screws are 4/40, the case cover screws are 6/32 and the chassis sheet metal screws are usually #4. - Speakers All Drake equipment is standardized to 4 ohm speakers. This impedance is important. Use of 8 ohm speakers will produce consid- erably less audio output and is not recommended. - Power Supplies The Drake vaccuum tube transmitters and transceivers use the same AC/3 or AC/4 supply. When using alternate supplies such as the Heath HP-20 or HP-23 ensure that the low voltage 250 volt supply is indeed this level. Do not provide more than 265 on this power line. - Transmitter switching For all receivers and transmitters in the 4 series the keyed voltage level is negative. The TR7 has a positive switch line. - Transmitter Driver Alignment Drake goes into considerable detail on use of a loading network to align the 4 series transmitters. Don't bother. Just align carefully for maximum transmitter output at a low drive level. The reason for this network is to simulate the loading when the units are used in transceive. The better method is to slave the units with the covers off both the receiver and transmitter and Drake Mods (10 Nov, 1995) 4 align. This is much faster and much safer than playing with the loading network method. There is some serious voltage inside these units. The loading network method is a waste of time. - Transmitter Tuning The 6JB6 tubes will draw considerable current. On the TR4, they can draw upwards to 450 ma. The T4 will draw 325 or so. When tuning up, keep the drive level on either unit to 150 ma or less until you're close to the final settings. Low PA tube life is usually caused by bias setting, operator, SWR, heat or PA neutralization. The 6JB6 tubes are being pushed a bit, but they should offer a good service life if properly set up, oper- ated and kept reasonably cool. - Transceive Operating Any of the 4 line separates will transceive amongst themselves but only within the same band and only within about 50 KHz, depending on the band. When there is a difference in the series set to transceive some minor inconveniences will be suffered such as loss of active PTO indication and the requirement of BFO netting prior to oper- ation. But it will work. - C Line Meter Switching The C line used an articulated LOAD control shaft that, when pushed in, would switch the meter from PA cathode current to relative out- put. The push required is considerable and is a result of the spring strip tension and the spring in the return switch. Never try to ad- just the tension of the shaft spring strip by squeezing it. The bend in the metal strip is a stress point and the strip will fracture at the bend. There are no replacement shafts to be had. If the tension is abnormally high, ensure that the shaft coupler and the shaft it- self are completely seated to the LOAD variable capacitor. - Transmitter Filiament Fuse Most Drake transmitters and transceivers have a fuse in the filiament power. This fuse may be a strand of copper wire or a pig tail fuse. It is a wise safety feature and prevents the wiring har- ness from going up in smoke should a tube filiament short. Pig tail fuses are hard to find and single strands are cheap, but a pain to create. Should your fuse open, install a fuse block for a 3AG fuse holder by bolting through one of the final cage perf holes. This is a no holes mod and worth while. Don't forget to find out why the fuse opened in the first place. Sometimes, they DO just 'go'. - Spare Parts - Drake Drake Mods (10 Nov, 1995) 5 Drake has in stock replacement parts for most of their equipment. For items that are in excess of 15 years old, this is very good. In most cases their prices are good. One can obtain coils, crystals, tubes, meters and relays. Final variable capacitors are available, but expensive. Most front panels are available for around $15.00 but Drake won't sell you a new one unless you return the old one. I do not know why, but Drake is adament on this policy. There are no accessories available of any consequence. You will not be able to buy Noise Blankers or Crystal Filters for any of the C Line. If you want crystal filters, there is only one known source - International in Florida. Their filters are much better than what Drake supplied and expensive. Well, maybe not that expensive con- sidering current KenYaeCom prices. And even their filters are infe- rior to Internationals. The lesson here is that essential parts are still available (until the stock is gone) at reasonable prices. If you need accessories for your R4C or TR7, best to get them with the radio. 1.2 WHAT DISTINGUISHED THE C LINE? ___________________________________ The differences between the B and C line receivers will be discussed in separate detail. Even the C line receivers were different as the years progressed. There is an overall difference between the C line and much of went before, however. The B line employed copper plated chassis. In the C, this was done away with. The C series also employed dual concentric dial plates where the B series and even the T4X used a single dial plate. The knob skirt on the C line was plain; on the B it was calibrated in KHz and on the TR4 this dial skirt just had radial markings with no numbers. Generally, in the receivers, Drake made optional on the C a number of things that were standard on the B. The B was a complete receiver out of the box; the C was not. The B automatically switched the AGC as the modes were changed; the C receiver had a 3 position AGC decay time con- stant setting that was independant of mode. Additionally, the C receiver allowed for more optional band select crystals. The primary reason for the triple conversion on the C was to allow for crystal filter selection and a notch filter. Pundits could argue the neccessity of this, but regardless, thats what Drake did. In the transmitters, Drake switched from a 6AU6 transmit mixer to a 6EH7 on the C line. This is a higher gain tube, but still, the B series did not suffer from a lack of drive. The 12BY7 was used as a driver tube throughout the 4 line. Drake used 6JB6 tubes for the final PA in all of their C and B line transmitters. In the transceivers 3 of these tubes were used to produce 200 watts output. On the separate transmitters, 2 of these tubes were used to produce about 150 watts on 80. Drake Mods (10 Nov, 1995) 6 Most of the changes in the C transmitter were for operator convenience. The C series most notably moved the switch for PA current from a sepa- rate control on the B to a switch that was activated by pushing the load control in. The C line also improved upon transceive operation of the separates by providing a separate line for the BFO . This alleviated the requirement to set the receiver and transmitter oscillators exact by the 'canary chirp' method. Additional switch lines were also provided to the dial lamps to indicate the active VFO when slaved together in the C line. Despite these changes, the B and C series could be slaved together. While the TR7 and TR4 were not transceive compatible with the separate receivers, they still provided for external receive antenna switching and external RX mute. Drake took measures to provide for an intermix of their equipment despite improvements to the gear as the years prog- ressed. 1.3 R4B AND R4C ________________ You could liken the Drake twins operationally to the Heath SB301 and SB401 from the fact that they would transceive. Stand alone SSB trans- mitters are all pretty much the same. The T4C is a bit like an SB401 functionally. In regards to the SB301, the Drake 4 line receiver, espe- cially the R4C, is in a completely different league. All Drake receivers in this series are sensitive and selective. On ei- ther series, a healthy receiver should exhibit noise peaking on all bands as the preselector is adjusted with no antenna connected. It will not be an extreme increase in noise level, but it should definitely be there on all bands. Drake enthusiasts generally prefer the B series receiver. The B series has built in a number of items that were options on the R4C. There are few mods for the R4B. When you buy an R4B, there is not much else to get - EVERYTHING is there that you need - noise blanker, calibrator and 4 selectivity settings. The B series was dual conversion, the last IF at 50 KHz determined the selectivity and provided notch filtering. The B receiver is noted for its clean recovered audio, good signal handling and solid engineering. Because the selectivity is determined by LC fil- ters, the skirt selectivity is not on par with crytsal filter radios. Since the B receiver was dual conversion and the C receiver is triple, it is generally assumed that the B receiver is 'quieter'. This will ap- pear from time to time throughout this treatis and I'm skeptical whether this is in fact true or yet another example of theory not born out in practice. The R4C is in fairly high demand. It is a triple conversion receiver and completely different from an R4B. While the R4B does contain some semi conductors, the R4C is more of a hybrid design. There were at least 3 different types of R4C receivers. Generally an early R4C has a 4 posi- Drake Mods (10 Nov, 1995) 7 tion crystal filter switch and a later model has a 5 position switch. In the later model, the AM filter location was moved inside the chassis and mounted on an extra bracket. There is no discernable performance difference amongst ANY of the Drake R4C series receivers. Collectors want the later model; practical owners don't care. The R4C - in all models - came with an 'OK' sideband filter. You will need to upgrade the filters and add some filters if you want to get this receiver to perform. There is only one source of filters for the R4C and that is International Radio in Florida. These filters are expensive (about $110 ea. US) and excellent. The most important filter is the 8 KHz first IF filter known as a GUF-1. Replacing the stock Drake filter with the GUF-1 transforms the receiver. If you have the 6 KHz GUF-1 in- stalled, noise blanker performance is compromised. A stock R4C is a bit of a waste. Under those covers is goodness just dy- ing to get out. When the R4C came out, there were some compromises that had to be made to keep the price point. The trade offs were mostly in the area of filters and no noise blanker. The first IF amp crystal fil- ter is a pretty sad excuse and unfortunately sets the character of the receiver. What you have to do to make it what it could of been is to ba- sically un-castrate it. With decent filtering and some (mebbe) mods, the receiver is as good as and maybe better than just about anything avail- able to date. Some aspects of the R4C design cause one to question the engineers at Drake. The audio amp in the R4C is frankly terrible, the power supply - especially the 12 volt supply - is an incredibly BAD de- sign. Drake had this 'thing' about running transistors from the plate B+ supply using huge dropping resistors and zener diodes. The power supply and audio stage together make very bad audio. This area of design causes stock R4C audio to be noisy, distorted, have a terrible frequency re- sponse and be 'brassy'. It is not nice to listen to, especially if you have heard the melodious 'B'. Given all these things to be said about an R4C, why would anyone want one? It depends if the C in question is loaded or not. The stock audio and power supply is offensive from a design aspect, but it does work. The transformation of the receiver with decent filtering is phenominal. What really happened to the C is that Drake cut costs and left the underlying receiver alone. That receiver base is extremely strong but the strengths are buried by the cost cutting. Aside from nostalgia what makes this equipment attractive is that it works, works well, is reliable and of high quality. The AGC on most of the receivers is superior to most foreign equipment. Considerable thought went into its design. It is overbuilt - you cannot break this equipment through age or use. While it may not have been built with the intent for it to still be working 20 years later, most of the Drakes I've seen have had a minimum of repair. All 'old' equipment suffers some abuse as it trades from hand to hand. Surprisingly, the Drake equipment seems to survive at the same level as Collins. Rarely is it butchered and then usually this happens from an inexperienced person attempting repair. Drake Mods (10 Nov, 1995) 8 Amongst Drake receivers a stock B is vastly superior to a stock C. The C receiver is an incredibly good receiver, but ONLY if it is loaded up with filters. The International filters are better than the filters that Drake supplied. The recovered audio on a stock R4C receiver is quite bad without some change. Just changing the value of 1 capacitor makes a considerable improvement. Once loaded up, the R4C beomes a real DX receiver and can 'slice and dice' with the best. The only way to over- load a properly set up R4C is to connect the antenna terminal directly to the transmitter, its that good. In stock form, you'd have no idea what is there. 1.3.1 R4C Evolution ____________________ The information contained here is accurate but not neccessarily a com- plete dossier on the R4C as it changed over the years. Updates will be made to this section as additional information is acquired. - R4C ser no above 16121 Revision date - Feb 1973 All mixer tubes 6HS6. First and 3rd mixers cathode injected. Second mixer is a dual gate MOSFET. The IF chain following the first crys- tal filter is 6BA6 1st IF, Noise blanker and then 2nd mixer. 4 posi- tion filter select. - R4C ser no above 18726 Revision date - March 1974 All mixer tubes 6HS6. First and 3rd mixers cathode injected. Second mixer is a 6BE6 with an JFET (2N5459) buffer. 4 position crystal filter selection. 3 diodes in series across the S Meter to compress the meter range. 2 S Meter zero pots were employed - one internal and one external. - R4C ser no above 21000 Revision date - Nov 1974 All mixer tubes 6EH7. First and 3rd mixers grid injected. Second mixer is a 6BE6 with an JFET (2N5459) buffer. 5 position crystal filter selection. Some intermediate models in this transition period may not have installed the new tapped IF transformer, T7C. Amongst the 3 series known, Drake spent considerable effort changing the mixers with particular interest in the IF chain following the 1st crys- tal filter. While no direct measurements have been taken, there appears to be little discernable difference between the first in this list and the latter. Drake Mods (10 Nov, 1995) 9 As can be expected, it is considered that the later model is superior to the early model. There is a natural tendancy to want to believe that this is true, but practical application does not seem to back this up. One of the attractions for some enthusiasts is the vaccuum tube process- ing of the RF signal in the belief that the early model dual gate MOSFET is automatically inferior. The fact that all models in the later series have an JFET in the RF chain is somehow strangely irrelevent to this position. Additional changes can be made to the audio and power supply if neccessary. Most other changes are subtle and amount to 'busy work' un- less there is a specific problem to address. 1.3.2 Sources of Mods ______________________ A number of sources did exist for mods to this equipment. Amateurs like to change equipment around. If the equipment is popular, it is not un- usual for a cottage industry to develop for some enhancements and goodies. Consider the following as reference only: - Sartori Associates (W5DA) Sartori offered for sale a number of accessories for the R4C and TR7 including solid state tubes (a 6BA6 was called a SBA6), crystal fil- ters, audio low pass filters and such. Most notable from Sartori was a killer 16 pole 1.8 KHz SSB filter for the R4C. - Sherwood Engineering Similar to the above, they provided R4C rework services and crystal filters. - Fox Tango Fox Tango was bought out by International about 5 years ago. F/T originally was noted for their Yaesu FT101 filters and first mixer kit changes. Regarding the Drake R4C, they offered add-ons known as GUF-1, GUF-2 and GUD. The first 2 were filters replacements for the first IF crystal filter in the Drake R4C and were for SSB and CW respectively. The GUD was a solid state product detector kit re- placement. - International Radio This company deals in after market crystal filters for a number of radios. The filters are about $110 and are good. Their filters for the Japanese radios are better than factory and much cheaper. Drake Mods (10 Nov, 1995) 10 It is difficult to find a better filter for a radio than from these folks. Most of their filters for all of the radios that you could buy for are drop in replacements. 1.3.3 R4B and R4C Mods and Tech ________________________________ - Voltage Regulation Early R4C receivers employed a 12 VAC secondary power transformer. Later model R4C used a 14 volt power supply by changing the power transformer. The early model supplies could fall out of low limit spec with marginal 110 VAC. While there is a Drake fix for this, the best option is to use an LM380 and lighten the power supply load. - R4B/early R4C LO Injection R4Bs injected the LO into the first mixer into the cathode from a low impedance link on T4. You can improve transceive injection from the transmitter and reduce spurs on 15 and 10 by replacing R7 with a 470 ohm resistor and bypassing it with a .005 uf cap. Run the in- jection to the grid of V2 pin 1 through a 10 pf capacitor from the high side of T4. Realignment of the front end is required after this change. - Low TX output in Transceive This may also show up as low(er) sensitivity of the receiver when transceived with the transmitter (B and C series). The cause is usually alignment or the injection cables. All RF cables (the C se- ries had 2) must be RG/62 low capacitance cable. It is best to align the receiver and the transmitter when slaved together. - R4C Audio (all series) Change C100 from .22 uf to .68 uf. Do not use a higher value. This will remove a lot of the raspy audio and clean up a fair bit of dis- tortion. Use a tantalum and observe polarity. - R4C Pass Band Bleed Through Replace first IF crystal filter with 8 KHz GUF-1. HIGHLY recom- mended. The stock Drake filter is 4 pole with 65 db stopband and a very poor shape factor. The replacement International filter has a stop band greater than 80 db and a good shape factor. This one sim- ple change will improve the receiver considerably. - Crystal Filters A stock R4C came with 2 crystal filters - an 8 KHz wide first IF and a 2.4 KHz second IF SSB filter. The first IF filter does not do the Drake Mods (10 Nov, 1995) 11 R4C justice. Replace this filter with the GUF-1 if at all possible. You can add a sharper SSB filter. I use 2.1 KHz. Why not a 1.8? Well, the 2.1 has nice 6/60 db figures. It puts up a nice flat band- width plateau without killing fidelity. For CW, a 250 Hz width is about right. The 125 Hz is just a bit too narrow and the 500 Hz is too wide for current band conditions. The 125 Hz makes the tuning and PBT control somewhat touchy. It rings surprisingly little and is a good CW filter. The 250 Hz is not all that much different except that the tuning requirements are more relaxed. Contact: International Radio, 3804 South US Hwy 1, Fort Pierce, FL 34982 407-489-0956 (TU-FR, 10:00 - 17:00 HRS) - R4C S Meter Balance (early model) Some early R4C receivers could not balance the S meter after prop- erly setting the AGC threshold (sensitivity control). Early model R4C receivers have only one trim pot for setting the S meter zero. Replace R33, a 470 ohm 1/4 watt with 680 ohm 1/4 watt. - Sensitivity - ALL The sensitivity adjustment affects S meter balance and sensitivity. Ensure it is no higher than -1.35 volts and no lower than -1.2. - BFO Bleed through R4C Early models could deflect the S meter while the passband tuning was moved across the IF frequency. Ensure all tube shields are in place. In extreme cases, check wiring harness layout and add a 47K 1/8 or 1/4 watt resistor from the base of Q5 to ground. - R4C Intermittant Crystal Calibrator The two shield plates that support the noise blanker are held by four #4 sheet metal screws from underneath the chassis. One of these is a short screw. Ensure that this screw is positioned for the plate near the chassis edge nearest the back of the receiver. A normal length screw will short the calibrator when the calibrator is seated down. - 50 KHz filter (late model) Seems to be applicable to serial nos 21000 and higher. Make a a 50 KHz network of a 10 mH choke and 1000 pf capacitor in parallel. Add a .01 uf 250 volt cap in series with one end. Install this network Drake Mods (10 Nov, 1995) 12 from pin 5 of V6 to ground. The receiver in question should have a T7C (not a T7 IF can). Lead dress for this mod can be critical and is noted by an increase in audio hash and hum. This change is applicable ONLY to R4C receivers that feed B+ to the plate of the 3rd mixer through the notch filter. - 50 KHz IF Coax (late model, early series) Late model R4C (tapped IF transformer T7C) could have some addi- tional CW crystal filter loss due to use of high capacitance shielded cable running from T7C. Replace this audio cable with RG/174 and change the value of C49 to 430 pf. You don't need this change if there is no CW filter installed in the radio. Your receiver is eligible for this change IF you have a T7C (NOT a T7) IF transformer and if C49 is currently 390 pf in your ra- dio. In this case, the coax in question will have a slightly larger diameter than the replacement RG/174 and will have a white colored center conductor. - R4C Audio (all) The audio stage in all R4C receivers is terrible. It is a lousy de- sign. Period. It causes a lot of heat to be generated, distorts, and has terrible frequency response. There really isn't much you can do about this except substitute an LM380 for the whole damn thing. Con- nect the output from the LM380 to the earphone jack. When connected here, the anti-vox will still work. The LM380 could be mounted on one of the support brackets for the noise blanker or, if you build a circuit board for it and use ground lugs ala Drake, you could use the 2 audio output transistor mounting screw holes. - Power Supply - R4C This is another extreme R4C weakness. It is an incredibly poor de- sign. The 2 resistors at the right hand edge of the board get very hot and will eventually cook the circuit board. One of these is the dropping resistor from B+ 150 for the PTO(!) Drake does this all the time in their equipment and it is a terrible design philosophy. You cannot properly fix the power supply unless you make the audio changes because the class A audio output stage draws 1/2 amp (!!) and hauls the power supply down. Once you have made the audio amp change, you can then install a 7812 3 A voltage regulator in the low voltage line in place of that power supply pass transistor. Eliminate some of the heat generated by pow- ering the PTO from the low voltage 12/14 line instead of the 150 volt line. Drake Mods (10 Nov, 1995) 13 There is another mod circulating that uses the filiament supply as a voltage boost for the low voltage line. Do not do this mod and if your receiver has had this change I strongly recommend you remove it and revert the supply to original. This mod cures nothing and actu- ally generates as much, if not more, heat. - AGC Transients R4C (early model) Verify that there is a network of a .01 uf and 1 Meg ohm resistor connected in series installed on the AGC board between the wire con- nect points on the board. This network is installed between the green/white wire and the yellow/white wire on the foil side. - AGC Pumping With Sharp Filters When good shape factor crystal filters are employed the AGC will pump when the calibrator is tuned right on the filter edge and the AGC is set to 'fast'. Excerpt July, 1976 Ham Radio pg 12: ".... designs with shape factors between 1.4:1 and 1.2:1 have two unpleasant side effects: 1. The extremely sharp skirt selectivity presents a problem for the AGC circuit because of high group delay and phase shift, which cannot be compensated for. In almost all .... 2. Point 2 ommitted Continuing, Rohde says ".... SSB reception should be between 1.9 and 2.4 KHz. .... (The) bandwidth on the famous KWM-2 was restricted to 2.1 KHz for this reason." Ignore it. You can't fix this without hurting the otherwise wonder- ful AGC. - 3rd Mixer Noise R4C Amateur 're-engineers' have claimed that an R4C weakness is 3rd mixer noise. Some of these amateur engineers have had a considerable 'go' at the third mixer inventing theoretical problems that gener- ally do not exist. It is the 1st mixer that sets the sensitivity of the receiver. By the time the signal gets to the 3rd mixer it should be processed enough to easily overcome 3rd mixer noise. And it does. If your receiver works well, leave the 3rd mixer alone. Drake employed considerable changes over the years to this area throughout the R4C series. Improvement in the receiver can be ren- dered by installing a pair of back to back diodes from the junction of C53 and C52 to ground. For 6HS6 injected 3rd mixers use 1N4148; for 6EH7 injection use 1N270. The diode type to use in the two cases of injection is important - do not use silicon where germanium is required! Drake Mods (10 Nov, 1995) 14 When Drake employed the 6EH7s as mixers, the injection was moved from the cathode of the 3rd mixer to the control grid. It is this connection that some Drake enthusiasts assume to be 'noisier'. There was also a Sartori mod that injected the LO signal into the third mixer from the bottom end of the secondary of the 3rd mixer grid input transformer. This mod follows good engineering practices and one of my R4C receivers has had this change. My other R4C, an early one, has the injection to the cathode of the 6HS6. I cannot tell much difference. - R4C Noise Blanker Do not use the blanker gain trim pot to make the receiver 'more sensitive'. It won't. Ensure the S meter deflection on the calibrator is exactly the same on 10 meters both with the blanker and with the 9 pin jumper plug. Excessive blanker gain will degrade the AGC by ruining the gain balance in the receiver and possibly al- low the BFO to bleed into the IF strip. - R4C IF and RF Amp Resistor Changes There have been previously published mods to change screen grid resistor values to improve sensitivity and allow for S Meter zero on early R4C receivers. This is a bad mod. It does not improve sensi- tivity and is overkill as a method for S meter balance. It increases the receiver gain and consequently destroys the good AGC charac- teristics of the receiver. Do not do this mod and if your receiver has been modified, revert to original factory values. - R4B Sensitivity Tune in the calibrator and then pull V10, the 12AX7 noise blanker clamp. If the S meter rises, replace the tube. A gassy 12AX7 will drive the NB clamp diode partially on, killing IF gain. 1.4 T4 SERIES TRANSMITTERS ___________________________ All of the Drake 4 line will transceive amongst themselves. Between the T4X and the T4C there was little difference. Most of the changes in the T4C from even the T4X were cosmetic or for better operator convenience. The B series used neon bulbs to indicate the active PTO when set up for transceive; the C line turned the dial lights on and off. A properly working T4any will give about 150 watts output on 80 meters, dropping to 40 or 50 watts on 10. The audio should be really clean and with properly operating ALC you should not be able overdrive the finals. There should be LOTS of drive on all bands. Drake Mods (10 Nov, 1995) 15 1.4.1 T4any Mods and Tech __________________________ - Can't Tune 10 Meter Driver Plate This is characteristic of 'generic' 6JB6 tubes. Replace with Sylvania 6JB6. Problem caused by high input capacitance of tube(s). - VOX Gain - T4X and T4B In cases where more VOX gain is required pick up the VOX input from the mic gain control instead of from the plate of V9b pin 6. When re-routing the audio pickup point, bypass pin 6 with a .05 uf cap. - T4C TX Lock up Lock up on a T4C is usually caused by a gassy mixer or 12BY7 driver tube. Other causes include leakage either to ground or B+ of the TX keyed line. This is a high impedance line. In extreme cases the cause can be T6. Inside T6 is a rubber washer that can contact the coil pins internally. The fix is to remove T6 and the shield and in- stall a fish paper washer between the bottom of the rubber washer and the bottom of the coil form. - T4C Side Tone - Elimination Standby CW sidetone sidetone may be eliminated by placing a 22 Meg ohm resistor between the pin in the centre of the circuit board in front of V7 (the one with the wire going to pin 1 of V7) and the lug at the top left of the board (the one with the 150K resistor). - Substitute VOX relay tube A 6AQ8 will replace the 6EV7 if a 47 ohm 2 watt resistor is added across pins 4 and 5 of V10. The tube change is is applicable across the entire 4 line (and TR3). The resistor IS NOT needed in any of the transceivers. Just swap the tube, in this case. 1.5 TR4ANY TRANSCEIVERS ________________________ The TR4 series represent possibly the BEST vaccuum tube transceivers ever made. The transceiver will easily put out 200 watts on 80 meters and 100 watts on 10. For comparison purposes, the unit is somewhat SB100 series like, but the TR4 receiver is much more sensitive on 15 and 10. Unlike the Heathkit, a noise blanker could be installed. It was only the very last TR4 that had an RIT circuit. The TR4Cany had a plug in relay; on the TR4, the relay was open frame and hard wired. All TR4 have a 9 MHz IF that is incompatable with other C line. They will not transceive with an R4any, but they will mute and T/R switch the antenna line. Because a 9 MHz IF and a 5 MHz VFO is used 20 meters is Drake Mods (10 Nov, 1995) 16 generated 'free', but tunes backwards as a consequence. If you suspect the crystal oscillator having a fault, check for output on 20 or 80. The TR4 had full 10 meter coverage; on the TR4Cany only 28.5 was in- cluded - the other 2 band crystals were options. There were 4 different series of transceivers that I am aware of: - TR4 (circa 1970) The basic transceiver. No RIT or CW filter. The AGC characteristics in the TR4 are better than any other transceiver in the 4 line, but the differences are subtle. Following this model a number of controls were moved for more operator conven- ience. Full 10 meter coverage. - TR4C The basic C transceiver. No RIT or CW filter. Dual dial plates. Some minor changes in the tube line up and 1 pf caps on the IF transfor- mers to get some more gain. Simplified RF amp AGC. - TR4Cw Some subtle internal changes. Dual dial plates. Has a 500 Hz CW fil- ter. No RIT. - TR4Cw-RIT The final model, sold for a period of time against the TR7. This model had it all - CW filter and RIT. It is distinguished by having the RIT control positioned in the lower right hand corner where the NB switch resided and having 2 pushbuttons in the lower center of the front panel. Over the years, the TR4 didn't change all that much. All models are noted for high TX output, sensitive receivers and for running hot. You need a fan. 1.5.1 TR4 Mods and Tech ________________________ The changes or mods for this equipment are few. The tube line up changed a bit - different 100 KHz oscillator tubes and such, but for all prac- tical purposes the radios performed about the same. - Increase IF Gain The TR4Cw had 1 pf capacitors across the IF transformer hot side (T11 and T12) to increase the IF gain. Since bandwidth is determined by the crystal filter, this had no effect on the receiver. Drake Mods (10 Nov, 1995) 17 - Different TX and RX Preselector Peaking Especially noticeable on 10 meters, its 'normal'. There is not much you can do about it. - Antenna Fuse Bulb This is located inside the final cage and is a #12 bulb. A #12 is 6 volts at 150 ma - exactly the same as a #47, but with a different base. This bulb is a bit silly, for it will take well over a watt of RF to open it. By then, the receivers ruined anyway, most likely. - Improved RX Audio On the TR4, C212 a .0015 uf on the grid of V17, a 6AQ5, should be paralleled with a .01 uf 300 volt cap. This will remove a lot of the brassyness and distortion. - TR4 Noise Blanker Quite a few transceivers were sold with noise blankers. Similar to other Drake equipment, the 34PNB is difficult to find by itself. The R4C noise blanker is unique from an TR4 blanker and cannot be mod- ified to operate in the transceiver for the following basic reasons: - Different IF frequency - Different on/off switching - TR4 blanker has bidirectional signal path 1.6 SPR-4 __________ This all solid state receiver is a essentially a solid state general coverage R4B. It is extremely sensitive and stable. The frequency is 'programmed' by installing the appropriate crystal - one of up to 23 into the sockets behind the band selector switch. There are few weaknesses or vices in this receiver. The AGC design is weird and in certain points, very high impedance. An 11 meg ohm input meter will drag the AGC down. The SPR-4 uses the same PTO and dial plates as the R4C. Some models were specially constructed for the FCC when they cared about the mess on CB and had the CB channels marked on the dial plates in red. It is done in an ingenious way and is fascinating to watch in action. Drake Mods (10 Nov, 1995) 18 1.6.1 SPR-4 Mods and Tech __________________________ - Sensitivity Measure the input resistance with an ohm meter at the antenna termi- nals on any band but 'A' or 'B'. It should be about 2 ohms. If it is not, likely the ground pin on the input matching coil has become unsoldered. This will be hard to get to and you'll be required to unscrew the slide switch on the back panel immediately above it. On 40 meters and above an SPR-4 will still 'hear' a lot of signals with the input link coil ungrounded. All thats coupling the antenna in this case is just stray capacitance and is surprisingly adequeate. If you have this problem, you'll notice 80 and 160 not to be too perky, yet the receiver aligns OK. - IF alignment The 50 KHz IF transformers tune broadly. The 50 KHz bandpass network coils accessible from the rear chassis panel tune sharply and are critical for proper sensitivity. Align with the bottom plate in place. It isn't easy, but this is the only way to get a good alignment. Do not disturb any of the wiring around this area of the receiver. - AGC The AGC in the SPR-4 is somewhat unique. The AGC controls on the back of the S Meter affect its strong signal performance. The AGC line is very high impedance. You cannot measure it successfully without dragging it down. The board behind the S meter contains the RF amplifier AGC. If you have problems setting up the AGC in exact accordance with the in- structions, replace Q14, the AGC FET amp. The AGC bus goes right to the gate of Q14 - any leakage at all will ruin the AGC. An MPF102 will work fine. 1.7 TR5 ________ The TR5 followed the TR7 and was announced for general market around 1982. It is a ham band only transceiver with a real synthesizer. It could best be described as being similar functionally to an FT77 or Swan MBX-100. It came with few accessories - there really wasn't all that much to add. It was an SSB and CW transceiver and did not cover the AM and RTTY modes offered in the TR7. The TR5 did include WARC band cover- age of the 10, 18 and 24 MHz sub bands. There is no PBT or IF Shift, but the TR5 did include a noise blanker. It could be looked upon as a 'baby TR7' for it is very similar in appearance. Instead of two rows of push Drake Mods (10 Nov, 1995) 19 buttons on the '7, the '5 has a single row of rocker switches, but the basic layout is much the same. The TR5 also had its 'own' line of accessories, most notably the L75 linear (single 3-500) and RV75 digital remote VFO. The RV75 would of course work with the TR7. Drake seems to have tightened up their specifications a bit since the TR7, especially in the area of third order intercept point. The TR7 was rated at +20 dbm at 100 KHz; the TR5 was rated at 0 dbm at 20 KHz. The TR5s rating is much more realistic. Additionally, this 0 dbm rating of the TR5 indicates very good strong signal handling ability. The dynamic range was rated at 85 db - a good, but not exceptional figure. Honest figures. The TR7s ratings are more akin to muscle car horsepower of the late 60's or hi-fi power output. This does not make a TR7 bad - its no worse than the 5 (at least). Its just that the TR7 figures were derived from rather optimistic measurement conditions. 1.8 TR7 ________ By the mid 1970's it was obvious that a new generation transceiver was required. Vaccuum tube equipment was being replaced by solid state ra- dios - especially for those that wanted to operate mobile. The solid state equipment was obviously the way of the future. Drake answered this challenge with the TR5 and TR7 transceivers. There also was an R7 receiver. This unit is not that common. Yes, there was a TR6. That was a 6 meter SSB transceiver circa 1970 in much the same vein as an SB-110. Yes, there was an 'A' model of the TR7. This is around a 1982 flavor. What the 'A' model of the TR7 and R7 really was all about is that the equipment contained standard such as noise blankers and crystal filters that were options on the earlier model. The TR7, as is common for most Drake equipment, is over built. This is characteristic of most well made American equipment. While a TR7 may not have all of the useless 'features' of foreign equipment, it is as reli- able as a rock and solidly built. Drake made sure it was a quality piece of radio and not intended to be disposable. An example - the TR7 gener- ates 150 watts (250 in or so) output, yet the PA is capable of at least 225 out. At its nominal power rating, the final transistors are under utilized. Most foreign PA stages do not have any where near this headroom. The transceiver is big and heavy at 17.5 lbs despite an aluminium chassis. Glass epoxy boards are employed throughout the radio. Half watt resistors are used even in the low power stages. The receiver is dead quiet and almost immune to overload. A large part of the reason for this is the lack of an RF amplifier and a strong passive DBM in the front end (ala Atlas 210). The TX SSB audio is rich and clean. The AGC switches with the mode setting for near optimum tailoring. The only item to be missed is an IF notch filter. Drake Mods (10 Nov, 1995) 20 A well working TR7 is a treat to use. Transmitted audio is excellent and the receiver is a gem. The major downside of the radio is its current requirements. Nominal drain on receive is about 3 A, on transmit, it could run to about 25 to 27 A. Both of these figures are considered slightly excessive today. The size of the radio rules out mobile oper- ation in most of todays cars and the red LED frequency display washes out in sunlight. 1.8.1 TR7 Mods and Tech ________________________ I have encountered few mods for this radio. This could be caused by the difficult nature of performing them or by the very fact that a stock TR7 is pretty good as it is. What makes this radio difficult to modify is the plug in board modules. This is good. This means that a TR7 is un- likely to be mucked with too severely. Your worst problem is likely to be alignment if your 'new' TR7 is a little sour. - Set Up The outlined procedures in the service manual are very well thought out and are presented in a linear progression. Follow them. The synthesizer set up is a bit tricky. Most important is to ensure that the 40, 13.695 and 8.05 MHz oscillators are exactly on frequency. If each one of these is within 100 Hz, then the readout, PBT and CLAR will 'naturally' fall very close to spec. Proper test equipment is essential to set up a TR7. - All Band Transmit Included with this article are additional TIF and TXT files outlin- ing Drake synthesizer changes for full receive coverage and full frequency coverage transmit. - Digital Display For a while the DR7 digital display was an option. A TR7 is signifigantly less without the DR7 display. If you are looking at a TR7 to purchase, make sure that it does indeed at least have this option installed. Of all the 'options' available for the TR7, it is unlikely you'll ever find a loose DR7 unless someone is cutting up a TR7 for parts. - The FA7 Fan This was an option on the TR7 except for heavy duty cycle use. Experience has shown that without a fan, even on SSB, the PA gets inordinately warm. Regardless of mode, some form of forced air cool- ing should be employed. The requirement is to provide air circu- lation, not neccessarily air cooling. The fan should be set up to blow in, not out. This might be contrary to the FA7 direction. Drake Mods (10 Nov, 1995) 21 The fan runs from 110 VAC and is meant to be run 'through' the PS/7. If you have a PS/7, a 110 VAC 'muffin' fan will bolt right on. If you use a generic power supply use a 12 volt version and power the fan off the TX Vcc from the PA stage. 24 volt DC fans will push a fair bit of air quietly and these are readily available surplus. - Receiver Sensitivity Check The calibrator should provide an S9 signal on 10 meters with no an- tenna attached if the alignment is close. Without an antenna, a properly operating TR7 should appear almost to be dead. If the RF gain is rotated fully CCW, the S meter should rest at the S9 +80 db mark - no higher or lower. Since there is no preselector to peak, the calibrator test assumes the S Meter is set up in accordance with the alignment instructions. The other alternative 'sign of life' tests you can do is to scratch the center pin of the SO/239 with a metallic anything. The S Meter should respond and you should hear the scritch noises most plainly in the speaker. You can also connect almost any antenna to the SO/239 and you should hear an increase in background noise, however slight - even on 10. - Receiver AGC Set Up Notes Aside from alignment, set up in this area has considerable affect on the receivers sensitivity and AGC 'personality'. Also important is the 10 volt regulator adjustment, for it too will have an effect on oscillator alignment, AGC and sensitivity. Tests indicate that at 9 volts, the receiver and AGC setup is quite 'mushy'. For all practial purposes, the 10 volt regulator adjust is the one adjustment that will determine how 'crisp' the radio is. - Transmitter Output Check A TR7 should produce 150 watts output on 80 meters if set up prop- erly. Current draw will be 22 amps at 13.6 volts. Use no smaller power cable than #12 for short runs and #10 for 15 feet or more. You should be able to disconnect the transmitter load and key the transmitter to full output. Properly set up ALC will limit the out- put 'power' to 20 watts or so. If you pull the blue wire from the ALC board (the one between the shielded cable and the red wire on the LHS), the PA stage will run wide open and I've measured over 225 watts output on 80 meters. Not recommended as a normal practice, but this is a good test of final transistor health. Set to its nominal 150 watt output, a TR7 is definitely loafing along. - Accessory Filters The TR7 filters are not interchangeable with the R4C filters. The R4C accessory filters are 5695 KHz and the TR7 are 5645 KHz. The Drake Mods (10 Nov, 1995) 22 factory supplied SSB filter is a 'fidelity' filter. Your transmitted audio with a properly set up radio and a microphone should sound like FM broadcast. The skirt roll off is just a little 'soft'. You need to go to a 1.8 KHz filter to get much RX improvement. The stock SSB filter is quite good in receive. The TR7 always transmits through the SSB crystal filter supplied with the radio. You can put the other 3 filters where ever you want, but don't mess with this filter in this position. - AM Filter An AM filter is almost impossible to find. You can fake an AM 'fil- ter' by putting a 390 ohm resistor through the input and output pins of any blank crystal filter position. It actually isn't bad. What is determining the selectivity is the 48 MHz first IF filter. - Transmit Power Pay particular attention to the SWR balance trimmer, C1901. ALC action is affected adversely by an improper null. This null trimmer also affects the wattmeter calibration, so if you change the trimmer setting, R2001 and R2002 will need adjustment also. Essentially, the FOR output is used for ALC and the REV output is used for shutdown. This is independant of the wattmeter setting. When you set up the ALC null, use a high impedance analogue meter, a non metalic align- ment tool and a good 50 ohm load. There are 2 control settings that affect the ALC. The obvious one is the 'ALC' control on the ALC board in the bottom of the transceiver. The other setting control is the gain pot on the predriver. This control sets the gain by setting the feedback on one of the driver stages. Properly set, you should have just enough ALC on 10 and as expected, a controllable abundance on 80 meters. Improper set up of the ALC usually means no ALC or will make the mic gain setting overly sensitive and the ALC clamp early on the lower bands. There is additional ALC/drive compensation from the bandswitch for the 10 and 15 meter bands. Extra resistors are switched in on these band settings to provide more drive/higher ALC threshold to provide gain compensation. For proper transmitter ALC action it is essential for the PA driver and final stages to be in good condition. 150 watts output should be easily attained on 40 and 80 meters. - External Speakers Unlike the '4 line, the TR7 employs an LM380 audio power stage. This IC is load tolerant and 8 ohm speakers may be used with no problem. - Microphone Drake Mods (10 Nov, 1995) 23 High impedance mics may be connected to pin 4. Input Z is about 750K, but this port is much less sensitive than pin 1. High Z mics are expected to be high output (> 100 mv). - PA Transistors MRF421MP will replace the SRF2337 final transistors. The MP indi- cates Matched Pair, so order one of these or two MRF471 and ask them to be beta matched. At this power and current level, it is wise to have current balance in this stage. MRF475 will replace the SRF2338 driver transistors. The collector is the mounting tab, so don't forget the insulating wafer. MRF476/2SC2166 will replace the TO220 predriver. The driver board changed over the years. The collector is the mounting tab, but its board placement is isolated from the circuit board. The cost of all of the above is about $90 from RF Parts. One final transistor alone is over $63 from Drake. The TR7 will shut down 50% at a 4:1 SWR. This provides more than adequate protection. However, the transmitter draws considerable current from a 13 volt supply. The supply should be rated at 30 AMP ICAS minimum. Marginal supplies and DC power cords will not provide enough current under load and likely will drop in and out under full carrier condition jeopardizing the PA. It is important that a stiff high current supply be employed with the TR7. - VOX The VOX requires about 50 mv of microphone input to trigger reliably from pin 1 on the mic connector. 1.9 R7 RECEIVERS _________________ The receiver is very similar functionally to an Icom R71A or Kenwood R5000. The R71A is an excellent communications receiver. This is excep- tional company to be associated with. This is a triple conversion receiver, somewhat like an R4C. The last IF frequency is at 50 KHz in order to encorporate a notch filter. The sig- nal flow is crudely similar to an R4C, but the unit is more akin to the receiver section from a TR7 with the following exceptions: - Notch Filter - Syncronous AM Detector - Provision for 5 filters Drake Mods (10 Nov, 1995) 24 - Will transceive with the TR7 - DR7 digital display was optional - Built in AC power supply - Receiver covers from 0 to 30 MHz w/DR7 - Selectable AGC - Selectable 10 db pre amp - Came without noise blanker ** ** The R7A did have the NB7A noise blanker installed, additional crystal filters and some minor rear panel changes. In order to use the syncronous AM detector properly, the optional 4 KHz filter needs to be present. **************************** END *********************************** Drake Mods (10 Nov, 1995) 25 2.0 DRAKE PRICES _________________ The following represent a sampling of the prices of various Drake equip- ment at the time they were sold. These are actual dealer prices and therefore there will be some variation. Unit Description Price hi/lo =============== =========== TR4CW Transceiver 799/699 34PNB Noise Blanker 100 FF1 Crystal Control 47 MMK3 Mobile Mount TR Series 7 RV4 Remote VFO 150 TR7 Transceiver 1295/1195 PS7 TR7 AC Power Supply 195 SLxxxx TR7 Crystal Filters 59/52 DR7 TR7 Digital Display 195 R4B Receiver 475 R4C Receiver 699/599 FLxxxx R4C Crystal Filters 52 NB4 Noise Blanker 70 FS4 R4C Synthesizer 300/250 SPR-4 Receiver 699 DSR-2 Receiver 3200/2950 SSR-1 Receiver 350 T4B Transmitter 495 T4C Transmitter 699/599 L4B Linear Amplifier 995 MS4 Speaker 33/30 AC4 Power Supply 150/120 DC4 DC Power Supply 165 7075 Desk Mic 39 1525EM Hand Held Mic w/TT 49 7072 Hand Held Mic 19 MN4 300 Watt Coupler 120 MN2000 2000 Watt Coupler 250 W4 Wattmeter 79 WV4 VHF Wattmeter 89 Price hi/lo represents the extremes of price range I've seen within the same time frame between dealers. This is in US $. Drake Prices 26 3.0 AUTHOR'S NOTES ___________________ Where comparisons were made to other equipment or indications of 'func- tionally like' were indicated, they were done for illustrative purposes only. I have heard manys a time Drake to be referred to as a "poor man's Collins." While I understand what is implied here, it is in a way an in- sult. Collins never really did make equipment for the Amateur. What ama- teurs got from Collins was commercial/miltary gear. Its analogous to saying a Kenwood TS450 is a poor man's SG2000. Its almost a meaningless statement. Drake, with the 4 line, made the best amateur market equip- ment available at that time in the whole world. So good, as a matter of fact, a large percentage of this equipment is in service today and will hold its own against the current crop of Japanese (what's obsolete this month?) radio candy, providing a real radio operator is using it. ________ The American equipment of the era of the 70's had a completely different engineering philosophy. I've stated before that Drake equipment is built to last. Additionally, just about every product in their HF line would work together in some form despite the changes and progress made over the years. You could connect an RV4C to a TR3 with but only a very minor change. This is in contrast to todays commodities that are replaced con- stantly with a whole line of new accessories. Rather than improve upon a radio, todays gear is replaced by the manufacturer en mass. While the parts availability from Drake won't last forever, you can still get them for a 25 year old radio. An S meter for an R4B is less than $15. I wrote this article for a few reasons. First, I wanted to publish what- ever maintenance tricks I had learned. I wouldn't want someone else to learn the hard way as I did. Life's too short. Second, I believe that it is important that mods and data regarding this equipment should be available. The intent of this paper is not only to put on paper some mods - I wanted to have some kind of a record indicating what this gear was like. Not only is this equipment part of our heritage, Drake and others made some excellent products. An increasing percentage of ama- teurs every year have no idea what Drake, Collins or even Hallicrafters were all about. This is not progress, folks. Its nothing less than for- eign domination of a unique market segment by makers of radio candy. In less than one amateur generation the absorbed dogma regarding 'features' that are essential for HF communication is sometimes difficult to stom- ach. Todays equipment has the soul and charisma of your average blender. Third, I am looking for some Drake accessories and this is a good way to advertise. If you should have the following for sale, please drop me a line: - 34PNB TR4 Noise Blanker - NB7 TR7 Noise Blanker - FS4 Synthesizer Author's Notes 27 - DSR-2 Receiver - R7 or R7A receiver - SL6000 TR7 AM Filter - FL6000 R4C AM Filter From time to time I'll be issuing additions and changes to this file as new data is acquired. I'm really not all that interested in getting into debates regarding comments made about an SB301 or about R4B vs R4C. I do know all of this gear very well, and you ain't gonna convince me other- wise. Oh yes - do have some fun, OK? Wayne Montague, VE3EFJ C/Serv (73057,3063) 4146 Marigold Crescent Mississauga, Ont Canada. L5L 1Y7 (current CallBook data is outdated) Author's Notes 28