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:

• TR4 (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 TR3.

  The AGC characteristics in the TR4 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.

• 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 transformers to get some more gain. The audio output stage in this and subsequent models employed negative feedback. Basically a plain TR4 with C line PTO.

• TR4Cw
  Some subtle internal changes. Dual dial plates. Has a 500 Hz CW filter. No RIT. Basically a TR4C with a 500 Hz CW filter

• 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 for activation of the NB and the RIT.

  The TR7 uses a very similar RIT circuit.

    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.