R.L. Drake

Drake Mods - TR4 Transceivers

Authored by VE3EFJ


    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 incompatible 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 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 included - the other 2 band crystals were options.

    There were 4 different series of transceivers that I am aware of:

    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.

    Most of the TR4any I see do not have the noise blanker. Pity. The 34PNB works very well. Typical for a transceiver of that era, there is no selectivity available other than the SSB crystal filter (or the CW filter, depending upon model). Just about any flavor of a TR4 will serve you well on sideband, but to get the RIT function, you need to purchase a TR4Cw-RIT or have a remote VFO. In this day and age, RIT is not as important as it was, for the people you are most likely to work will be more stable than you are. It is *they* that will be using RIT. The DC3 or DC4 will allow the TR3 or TR4 to go mobile, but the radio is just too big for most modern cars. There is no reason why you cannot operate one mobile, but you'll need a mindset for installation that goes beyond connecting a 2 wire 12 volt cable to the back of the radio. The filaments alone consume as much power as a Scout puts out.

    It is possible to install an RIT circuit into the earlier model series transceivers by duplicating the Drake RIT circuit. Your greatest challenge will be to add in the appropriate controls without butchering the front panel, unless you don't care about it. Within 10 ms of taking your Black and Decker to the front panel, that TR4 of yours is worth .... nothing. You cannot make a homebrew RIT by rubbering the band crystals because 80 and 20 do not use band crystals. An alternative RIT is to find an RV4 or RV4C. The chance of finding a TR4Cw-RIT is real slim and expect to pay if you find one. It is not too practical to attempt to retrofit the CW filter, however, since this requires replacing the sideband switch and building mounting brackets. I have heard that Drake will upgrade a TR4C to a TR4Cw for $105. This is a good deal.

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