[MRCA] [Milsurplus] [MMRCG] Speculations on ground radios of the fifties

Wed Apr 29 21:07:47 EDT 2026

Some background on the RCA mod of ARC-38. From a 1961 USCG publication.
PDF Attached

Why am I doing these searches? - I don't give a flip about airborne
radios! I just get caught up chasing down web ratholes...

Nick England K4NYW
Chapel Hill NC
www.navy-radio.com

On Wed, Apr 29, 2026 at 8:37 PM <frledda at att.net> wrote:
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> Thank you, Nick!
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> About the ARC-21…..  It states that it was pushed to service when still “half baked” due to pressure from the Korea conflict.  RCA was no dummy! They knew what they were doing, but little can be done when they tell you to light the fire and start production before the design is fully baked. You go and hope that a small retrofit or rework will solve the problems.
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> I have never seen an ARC-21 but I have read a portion of its manual.  It is and impressive radio, and my impression is that it was technologically innovative, but need it some refinement.  The first time I make it work, and the second time, I make it right!
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> I read that the size of the ARC-21 and some of the issues, opened the door to Collins ARC-38 to the Navy!  No doubt that the ARC-38 was a great radio.  I like to know how RCA got to do the ARC-38A….
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> Best, Francesco K5URG
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> From: milsurplus-bounces at mailman.qth.net <milsurplus-bounces at mailman.qth.net> On Behalf Of Nick England via Milsurplus
> Sent: Wednesday, April 29, 2026 6:53 PM
> To: Jim Whartenby <old_radio at aol.com>
> Cc: mrca at mailman.qth.net; milsurplus at mailman.qth.net
> Subject: Re: [Milsurplus] [MMRCG] Speculations on ground radios of the fifties
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> Interesting procurement history here on ARC-21, ARC-38, etc.
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> https://books.google.com/books?id=I3NaEkHwo6MC&pg=RA100-PA20&dq=%22an/arc-38%22&hl=en&newbks=1&newbks_redir=0&source=gb_mobile_search&sa=X&ved=2ahUKEwiZ1K24npSUAxXIKVkFHUYzLTAQ6AF6BAgLEAM#v=onepage&q=%22an%2Farc-38%22&f=false
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> Nick England K4NYW
> Chapel Hill NC
> www.navy-radio.com
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> On Wed, Apr 29, 2026 at 7:08 PM Jim Whartenby via Milsurplus <milsurplus at mailman.qth.net> wrote:
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> Nick
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> I have the feeling that the 1951 contract date is way too early for production so it must be a contract let for R&D.  This would eventually deliver the first article for specification and environmental testing.  The 1956 date would be for actual ARC-38 start of production as I have a Collins ARC-38 preliminary service manual printed by Collins which is also dated 1956.
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> I looked for the AN/ARC-38 in the Collins Signal and found nothing but the 618S-1 is listed.
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> Looked in the Electronics Equipment Index, NAVSHIPS 92563B, circa 1963 and the ARC-38 is not listed.
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> My gut feeling is that the SMO took much longer to develop which delayed the ARC-38 so the 618S-1 was sold commercially.
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> Thoughts?
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> Jim
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> Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy
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> On Wednesday, April 29, 2026 at 04:06:40 PM CDT, Nick England <navy.radio at gmail.com> wrote:
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> FWIW, ARC-38 is listed in the Navy Supply Office catalog with 1951 and 1956 contract dates. Navy BurAer listed as design cognizance.
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> https://www.navy-radio.com/manuals/94200/94200.1a_9-5.pdf
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> Nick England K4NYW
> www.navy-radio.com
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> On Wed, Apr 29, 2026 at 4:32 PM Jim Whartenby via groups.io <old_radio=aol.com at groups.io> wrote:
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> Ray
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> The first airborne synthesized, fully automatically tuned, HF transceiver would be the ARC-21, made by RCA.  It is an AM transceiver or "double sideband" as RCA would describe it which was also capable of CW operation.  It also used RCA designed mechanical filters, two as IF filters and one as the BFO oscillator for CW operation.  Perhaps this is the first use of mechanical filters in a military radio?  It does not use 400 cycle power as all of the servo tuning systems are DC powered.  It is capable of 100 watts RF output over the frequency range of 2 to 24 mc with 500 cycle increments over all frequencies.  It was designed for the first jet bomber, the B-47 and it's support aircraft.
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> Some five years or so later, SSB became the main mode for communications so in order to recoup the investment in equipment already on hand, the ARC-65 was developed.  This modification was done by replacing the modulator, power amplifier and reference oscillator with most of the other modules of the ARC-21 remaining with appropriate modifications.  With this successful experience, RCA was tasked with doing the same for the ARC-38.
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> The ARC-21 is listed in JANAP-161 as is the 618S-1 but not the ARC-38.  I'm not sure why this is so as it is my understanding that the ARC-38 was in development before the release of the 618S-1.  Perhaps the ARC-38 was only used by the Navy so it was not listed in JANAP 161?  Both are wired to accept the SMO, servo amplifier and 500ks oscillator, IIRC, so I suspect that both were in development concurrently by Collins.
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> As for the Army not converting to SSB, weren't they more impressed with VHF FM?
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> Regards,
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> Jim
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> Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy
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> On Wednesday, April 29, 2026 at 10:05:12 AM CDT, Ray Fantini via groups.io <rafantini=salisbury.edu at groups.io> wrote:
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> 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.
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> 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.
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> 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.
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> 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
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> 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.
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> 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
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> Ray F/KA3EKH
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