[R-390] 390A test jigs

Fri Feb 16 16:03:22 EST 2018

The R-1247 was not developed for NASA (who never had any of them), but 
was part of a frequency-synthesized, SSB upgrade for the AN/GRC-26D ratt 
van, done under contract for the Air Force by Manson Laboratories.  The 
R-390As were modified by Manson to provide relay-switched inputs for two 
external synthesizers, one substituting for the receiver's internal 
crystal oscillators (called a "stabilizer"), the other substituting for 
the internal 2.455-3.455 Mc PTO.  The T-368 transmitter was also 
reworked for SSB--the modulator and PA were removed, and a SSB exciter, 
synthesizer, and  a new linear amplifier PA deck were installed.  These 
modified GRC-26Ds were re-named AN/GRC-129.

Manson also did a synthesizer upgrade for the Air Force's AN/FRR-41 
receivers.  I have one of these receivers here.  Called the Manson SBM-1 
"Stabilization Kit", these were designed to be easily field-installable, 
with no significant modification to the receiver other than a few 
mounting holes drilled into the rear panel.  They used adaptors 
containing switching relays which plugged into the tube sockets of the 
receiver's various oscillators, and the tube would then be plugged into 
the adaptor. Cables were routed out to a bracket added to the rear of 
the receiver contained coax connectors and a control connector for the 
synthesizer inputs.  Similar adaptors were also supplied for the 
FRR-41's two CV-157 ISB converters.    The synthesizer units were 
similar to, but not identical to those used in the R-1247.  The 
stabilizer provided an additional 555 kc and 100 kc injection for the 
two CV-157s, and the synthesizer had an extra PLL and tuned in 100 cps 
steps, vs the 1kc steps of the AN/GRC-129 system.  No change in 
nomenclature was made to the receivers or converters after installation.

These modified FRR-41s were used by the Air Force for high-speed (3000 
bits/sec) ISB HF data links  up and down the Eastern Test Range.  NASA 
did have a couple of these modified FRR-41s, but they were quickly 
dumped due to difficulties with the synthesizers. All these were 
subsequently replaced with the greatly superior TMC DDR-506 diversity 
receivers, which were used from about 1966-1980.

The R-390A stabilizer adaptors were considered undesirable by hams, 
mainly because the PTO adaptor adversely affected PTO linearity.  They 
were virtually always removed and discarded. Paul appears to have found 
a loose set.

73,

John K9WT

On 2/16/2018 2:05 PM, Steve Toth via R-390 wrote:
> My understanding about the Manson labs receivers (I'm doing this of the top of my head, so help me out group if need be), was that Manson Labs produced and converted R390A's for NASA starting with the Apollo space program.  They also produced an in-field conversion kit so the conversion could be done on-site.  The conversion enabled the R390A to be used with external precision oscillators for precise frequency control and stability.
> After the conversion the R390A became an R-1247.  The only physical appearance difference was three additional BNC interface jacks for the external equipment mounted on a plate mounted on the rear panel below the standard IF output jack and above the terminal strip and possibly no nameplate designating it as an R390A (I happen to have unintentionally acquired one of these receivers).
> So maybe this is one of the in-field conversion kits? - Steve  W7SJT"Always look for a positive solution then Improvise, Adapt, and Overcome"- adaptation of the U.S. Marine Corps motto
> "Every day is an opportunity to challenge the achievement of your dreams"
> "Success is not final, failure is not fatal.  It is the courage to continue that counts."- Winston Churchill
>
>
>   
>
>        From: Tom Chirhart via R-390 <r-390 at mailman.qth.net>
>   To: W4QG <w4qg at cfl.rr.com>
> Cc: R-390 at mailman.qth.net
>   Sent: Thursday, February 15, 2018 6:36 PM
>   Subject: Re: [R-390] 390A test jigs
>     
> These are mods made by Manson Labs to the R-390/A..
> 73
> Tom
> K4NCG
>
> Sent from my iPad
>
>> On Feb 14, 2018, at 5:58 PM, W4QG <w4qg at cfl.rr.com> wrote:
>>
>> All,
>>
>> I acquired a set of 4 devices which appear to be test fixtures/jigs. They appear to be commercially made.
>> They have markings similar to what would be found 390(A) modules.
>> Stamped on them is "R390A" "CODE 26916" and the part numbers 150-017274, 150-017275, 150-017276, 150-017277
>> I've looked through my meager documentation and can't find any reference to these.
>> Can someone give me some info on them?  (pictures available if anyone is interested)
>>
>> Thanks,
>> Paul W4QG
>>
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