[Milsurplus] thoughts on the SRR family of radios - kinda long.

[Kenneth G. Gordon]

On 9 May 2016 at 11:24, Nick England wrote:

> I like them fine too Ray, but your timing is off. These receivers were primarily replacements for 
> the pre-war RBA/RBB/RBC and RAL/RAK receivers, and pre-dated the R-390A. They were 
> replaced shipboard by R-390A + CV-591 for FSK/SSB (and later by R-1051).
> They were part of the Navy's big change in maintenance philosophy from component 
> replacement to modular replacement that happened post-war.
> 
> The series included the following -
> AN/SRR-11, -12, -13 shipboard LF, MF (rare), HF
> AN/FRR-21, -22, -23 shore station LF, MF (rare), HF
> AN/MRR-1, -2, -3 mobile in a waterproof case and 24v p/s option LF, MF, HF, (all very rare)
> AN/FRR-32 dual diversity HF with two R-618/FRR-32 receivers (modified FRR-23 I think)
> AN/FRR-18, -19 shore station 4 channel xtal control (or tunable) LF, HF (very rare)
> 
> Nick England K4NYW
> www.navy-radio.com

Thank you for the accurate historical and type information, Nick.

Some time ago, I was "gifted" with about 5 tons (yes, tons) of radio equipment by an old 
employer (1970s), all military surpus, mostly receivers and some test equipment. I had to 
sell off all the better stuff since at that time our growing family needed the money.

Amongst the pile were quite a number of the SRR family of receivers. I sold the NIB 
FRR-23, and an almost new SRR-13, but have had to keep all the rest since all of those 
needed some maintenance to put them back in decent operation.

I have one SRR-12, a few SRR-13/13A, and a larger number of SRR-11 models since the 
fellow I was working with was doing experimentation at VLF, recording the signal levels of 
all the Navy and some foreign VLF transmitters at his location in Missoula, Montana, 
correlating those signal levels with sunspots.

There is a phenomenon called SES for Sudden Enhancement of Signals at VLF in which the 
appearance of a "new" sunspot or CME will, shortly, be followed by a very sudden rise in the 
received signal levels of a VLF station, followed by an exponential fall off to normal levels.

Anyway, he first began using RAK receivers for this purpose, since those exhibited this very 
noticable signal rise directly at the audio output far easier than receivers which had AGC. 
After some time, he then began using more modern receivers, including the SRR series, 
and had to modify his recording methods to use the AGC voltage as an indicator instead of 
audio output levels.

At the time, I was his electronics support (he was a psychologist), and when he tried to use 
the SRR-11s running 24/7/365, he began to suffer repeated failures of one component or 
another due to the extreme build-up of heat in the enclosed cabinets.

After studying the schematics for a while, I soon discovered that the screen voltages of all 
the tetrodes and pentodes in the receiver were exactly the same as the plate voltages. 

Although according to the tube manuals, this was a normal way of using the tubes, I felt that 
this factor was allowing the tubes to be run, constantly, at their maximum rated plate 
dissipation rating. 

I then experimented with one receiver, an SRR-11, by modifying every module to include a 
properly bypassed 56K ohm dropping resistor in the screen voltage feed. The result was 
that the heat produced dropped dramatically, and we no longer had heat-related failures.

Furthermore, I was not able to detect any reduction in the performance of the receiver.

My employer then insisted that I do the same thing to all his other SRR-series receivers, 
which I did.

I have used an SRR-13A here for some time a few years ago, and was actually fairly 
impressed with the way it worked. It was quiet, sensitive, and the dial accuracy was quite 
good.

I was also very impressed with the subminiature tubes used in them. If those tubes are 
operated conservatively, they will, literally, last forever. 

However, they are what I would term being "abused" in many pieces of equipment which 
used them, especially some of the military equipment. I have heard from ex-military folks 
that with some of the military gear which used certain of those tubes that the tubes were 
extremely unreliable in that service, yet the subminis were originally designed for use in 
proximity fuses, and some were rated for 10,000 hours of life in normal use.

As soon as I get my shop back in condition, I want to restore a good SRR-11, the single 
SRR-12 I own, and an SRR-13A and put them in operation.

Ken W7EKB