[Milsurplus] SRR-13 basic questions

[Ken Gordon]

On 18 Jul 2024 at 22:49, Jim Whartenby via Milsurplus wrote:

> 
> Hue
> My impression is that it is heavy because it was sold to the Navy!

Ha ha! Ain't that the truth?

> 1) The SRR modules are heavily shielded.  Every connection on the
> back of the case is decoupled to keep noise out of the receiver. 
> Even the chassis is broken up into partitions.  Each module base is
> cast aluminum with lots of metal shielding to enclose everything
> inside the module.  Finger stock is used everywhere to ensure the
> integrity of the shielding.  The slides that connect the chassis to
> the case and the box containing the big variable capacitor both
> appears to be steel.  I would not be surprised if there is brass,
> mu-metal and stainless steel somewhere else in the mix.

Yes. IMHO, they are VERY well built. I like the circuit design too. I DO have some issues with 
the implementation of the deisgn, though.

> 2) The "arms" you refer to: are they the steel slides or the handles on
> either side of the front panel?  The handles appear to be cast
> aluminum.  I have scrapped a few SRR and FRR radios that survived a
> garage fire of the late Dr. James Black.  I got more then a dozen of
> these radios at his estate auction.  So I have many spare parts,
> including the handles.

I also have many spare parts.

> 3) I have been servicing equipment that uses subminiature tubes for
> quite a while now.  I have only found one bad tube out of a dozen or
> so that I replaced.  The bad subminiature tube had an open heater,
> all the rest were good in that their replacement did not cure the
> problem I was trying to fix.

Reading up on those submini tubes is a fascinating adventure. Those tubes are fantastically 
reliable. Several of the type were used in proximity shells. Sylvania designed most ot them.

I regard them as possibly the pinnacle of tube development.
  
> The SSR and the later FRR radios are not the same but some modules
> appear to be interchangeable.  The front end modules are different
> regarding the antenna and RF modules, not sure about the mixer and
> oscillator modules.  The first detector and everything later appear
> to be identical but I have never tried to swap them out to see if this
> is fact.

Me either.

> I would suggest that you set up the power supply for operation on 400
> cycle power.  This adds a primary winding which will lower all
> secondary voltages a bit.  This way you won't have to worry too much
> about subminiature tube life.  

In my expernence, reducing screen voltage on those tube to which you can do it drastically 
reduced tube dissipation, severely reducing heat.

> If one band appears to be deaf, check
> the associated antenna coil.  I have found several that were burned
> open.  Not much room aboard ship to separate TX and RX antennas!

Agreed. In fact, I have a section of my website which shows how to rewind any such coils.

> They are nice radios and the projection dial has a coolness factor
> about it. Regards, Jim

I really like that projection dial. Thanks, Jim.

Ken W7EKB