[Milsurplus] AN/SRR** radios

[Kenneth G. Gordon]

On 30 Dec 2016 at 6:48, antqradio at sbcglobal.net wrote:

> I looked through the Rovero document but didn't find anything on frequency drift. 
>  Ken, can you be more specific on location?

There is nothing on Rovero's site about drift. That was, apparently, only a problem with the 
very early models and has been covered in that strange document we found on a website 
some time ago. I'm sure you remember that one.
 
> The SRR-13A and FRR-23 that I have repaired do not seem to suffer from any 
> significant drift.

None of mine ever did either. I thought they were unusually stable.

>  Either one, once set to WWV at 10 mc, will come back up from a 
> cold start on frequency as soon as the receiver is up and running; takes about 
> two minutes.  They seem to stay on frequency for hours with no need to touch up 
> the tuning dial.

That follows my experience with them too.

>  Both radios are stock but I have changed the power transformer 
> primary taps.  The 125 volt tap on one side of the primary and to the 400 cycle 
> tap on the other which further lowers the filament voltage to about 5.9 to 6.0 volts 
> and a correspondingly lower B+ voltage.

The 400 cycle tap is an excellent idea which I had never thought about, although I did 
always set the tap to the 125 volt connection.

>  There are other minor fixes / preventive 
> measures that I would be happy to share if there is any interest.
> 
> Ken is correct about the coils in SRR-13A receivers having issues resulting from 
> corrosion.  I have had several RF coils / transformers that are open and found it 
> easier to just replace rather then rewind.

Well, I rewind because I don't have a lot of spares, although I do have several junkers which 
I have used for parts.

>  There seems to be fewer variations in 
> the RF coils / transformers then the part numbers suggest

Yes. Correct.

> so I have been able to 
> replace open units from other modules from scrapped receivers.  Those radios 
> that were scraped had smoke damage and were missing some modules and dust 
> covers.  All of the SRR-13A receivers, around 12,

Wow!!! :-)

> that I got came from an auction 
> of the estate of James Blackmon, who was a medical doctor and avid radio 
> collector here in Arkansas.
> 
> To be fair, several levers were found to be cracked where the lever connects to 
> the module.  I attribute the lever issue to what was referred to as "brogan 
> maintenance" in tech school.  It seems to be easier to torque the 4-40 screw then 
> to lube the binding mechanics. This same issue is also found in the Collins R-390 
> Oldham couplers, for the same apparent reason. 

Yes, although many of the earlier crank-arms were made of some sort of almost pot-metal 
and were far more prone to crack than the later ones. Even so, Josh Rovero's site shows an 
article by another ham (can't remember his name right now, Bartolick?) which shows how to 
make new ones which are far stronger. However, the work required is somewhat 
time-consuming.
 
> Ray, is your receiver an SRR-13 or SRR-13A?  I have several SRR-13A 
> receivers and one FRR-23 but no SRR-13 examples.  I wonder if the frequency 
> drift problem was addressed in the later SRR-13A?  The only difference that I 
> have noticed about the SRR-13 as compared to the SRR-13A or FRR-23 HFO is 
> that the later uses a triode oscillator while the SRR-13 used a pentode.  All other 
> passive components seem to be identical in either HFO.

As I understand it, one BIG difference between them is that the 13 used LC filters in the IF 
while the 13A used RCA-designed and built mechanical filters...but perhaps I've 
misinterpreted my information.

> The SRR-13A has the same "cool factor" for me as the R-390A.

Ha ha!! Yes! I really, really like the SRR receivers.

>  Neat 
> mechanics, interesting frequency display and the heft factor of a cold war era 
> military receiver. 
> Funny, never had a bad RCA mechanical filter in an SRR-13A.

Exactly!!!!! I had "heard" that those filters were very, very reliable. I have never seen nor 
heard of a bad one.

>  Wish I could say 
> the same about the Collins R-390A!

Yes. Same here.

Ken W7EKB

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