Authored by VE3EFJ
9.0 TR-4ANY TR-ANSCEIVERS
The TR-4 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 TR-4 receiver is much more sensitive on 15 and 10. Unlike the Heathkit, a noise blanker could be installed. It was only the very last TR-4 that had an RIT circuit. The TR-4Cany had a plug in relay; on the TR-4, the relay was open frame and hard wired.
All TR-4 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 TR-4 had full 10 meter coverage; on the TR-4Cany only 28.5 was included - the other 2 band crystals were options.
There were 4 different series of Transceivers that I am aware of:
 | TR-4 (circa 1970) The basic transceiver. No RIT or CW filter. There were 2 models of this first transceiver. An 'early' model and a 'later' one. The early model was a transitional model from the TR-3. The AGC characteristics in the TR-4 seem different than other transceivers in the 4 line, but the differences are subtle. After this model, Drake made some subtle changes in the AGC amplifier, V13. Full 10 meter coverage. |
| TR-4C 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 transformers to get some more gain. The audio output stage in this and subsequent models employed negative feedback. Basically a plain TR-4 with C line PTO. |
| TR-4Cw Some subtle internal changes. Dual dial plates. Has a 500 Hz CW filter. No RIT. Basically a TR-4C with a 500 Hz CW filter |
| TR-4Cw-RIT The final model, sold for a period of time against the TR-7. 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 for activation of the NB and the RIT. The TR-7 uses a very similar RIT circuit. |
Over the years, the TR-4 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 TR-4any 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 TR-4 will serve you well on sideband, but to get
the RIT function, you need to purchase a TR-4Cw-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 TR-3 or TR-4 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 TR-4 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 TR-4Cw-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 TR-4C to a TR-4Cw for $105. This is a good deal.
