[MRCA] Speculations on ground radios of the fifties

[Jeep Platt]

I had an R-808 and it was very mediocre.  It had in internal Rtty loop supply.  Regarding the
T-195( ), the matched diodes in the servo system were critical match. The TM called out for a time in use change for them.  Also, the T-195 liked to see 28.5 to 29v for best servo op.
K3HVG

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From: mrca-bounces at mailman.qth.net <mrca-bounces at mailman.qth.net> on behalf of Ray Fantini via MRCA <mrca at mailman.qth.net>
Sent: Wednesday, April 29, 2026 11:05:08 AM
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Cc: mrca at mailman.qth.net <mrca at mailman.qth.net>; MMRCG <mmrcg at groups.io>
Subject: [MRCA] Speculations on ground radios of the fifties

Want to Thank Nick for posting the info on the R-808 and GRC-14, over the years have owned a couple of radios but never any of the GRC-14 family of components. Would assume that it's somehow a competitor of the GRC-19, R-392/T-195 but never as successful. The ARC-38, 618, T-195 and T-631 are all using the dual winding servo tuning systems along with 400 cycle Chopper / Discriminator systems for PA and Antenna tuning, maybe the first true Autotune system developed. Remember that allegedly autotune radios like the ART-13 and the like are only radios with mechanical presets where the servo radios like the ARC-38 have a true automatic tuning system that thru the use of discriminators can arrive at a solution for   PA and antenna resonance.
Spent many hours learning the ways of the ARC-38 and 180 L tuners, dealing with phase relationships and mechanical conversions of small DC voltages to high AC voltage to drive system. Similar system on the T-195 and the 618 family of SSB transceivers. The GRC-106 amplifier employes the same idea of discriminators and resonance balance but relies on the operator to be the motor.
A weird quirk of the T-195 was that they pushed the capability of the autotune a little too far maybe and occasionally the radio would not achieve a tuning solution, I always suspected that this was a result  of attempting to do both PA and Antenna match in one stage. Don't know if that's the case or not. But looking at the design of the GRC-14, they may have resolved that issue. It's going to annoy and aggravate a bunch of people out there but just looking at the manual have to say that although I never worked on or used the GRC-14 it may be a superior set to the Collins GRC-19, but at least the GRC-19 is lighter than a GRC-14 and smaller too.
GRC-19 sets were everywhere, least until the death of AM and still held out in RTTY ops until the GRC-106 came along but the GRC-14 appear to only have limited use and were quickly phased out as soon as SSB was adapted as a standard. Too bad no one ever reverse engineered the GRC-14 sets for SSB like the ARC-38A
Another question would be why the ARC-38A happened ?  The basic ARC-38 was a groundbreaking autotune transceiver with its self-tuning , variable IF and mechanical filters. It was years ahead of anything else out at the time. But by the sixties everyone knew SSB was the way HF communications were going, and the 618T was still in development, so how did it happen that someone decided to do the huge conversion from AM to SSB? And why when it was a Collins design, did RCA get the job? I like how RCA would also paint over the front cover, so you would no longer see the big Collins logo or name.
Also have to wonder why there was no attempt to re fit the R-392/T-195 (GRC-19) for SSB? Once again just looking at the book think it would have been easy to re-work the GRC-14 stuff then deal with how densely things were stuffed into the GRC-19


Ray F/KA3EKH
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