[Milsurplus] [MMRCG] SR Systems SR-206

[Robert Nickels]

On 9/18/2023 10:31 AM, Ray Fantini wrote:
> Hard to love channelized radios where you have lots of tuned assemblies that don't lend themselves  to much spread even if you use an external synthesizer.

Ah Ray, but the fun-filled hours reverse-engineering the  thing without 
a schematic is such a great learning experience ;-) Here's mine:

https://i.imgur.com/pzR5tKi.png

I did the conversion because this one came with a pretty complete set of 
band modules.  Without that it might have only been capable of operation 
on one or  two bands and not worth the effort.   As usual,  I set the 
channel switch up to act as a bandswitch and tuned them to the HF Pack 
or AM window freqs on 75/60/40/20 meters.  Typically the fix-tuned RF 
boards will give full power over a span of 50 kHz or so.   The 210 uses 
a Collins mechanical filter, which produces nice audio but has kind of a 
strange conversion scheme for USB/LSB if I recall, being 
double-conversion.     But it only requires one frequency per channel 
frequency, so a simple external synthesizer was used, set for the proper 
IF offset.    As I often do, one of the front-panel holes was repurposed 
for a 1/8" stereo jack for the synth.    In this case it was a VOX 
switch which isn't missed because the VOX board was not installed.     A 
wide range of option boards were offered by SRS, all at additional cost 
of course!

The SR-210 used three 6146s in the PA so it was good for more power than 
most.  It was early enough that not only the driver but also the first 
receiver RF stage used tubes.   High quality components were used and 
construction quality is good commercial grade.  The SR-206 was a 
6-channel version that was used by the US Coast Guard.   The later 
SR-204 was a more compact 6 channel transceiver that that evidently was 
on the production line when SRS closed up shop as a number of 
partially-build subassemblies ended up at Surplus Sales of Nebrasaka.    
I have an SR-204 but it has not been converted yet.

The SR-206 and SR-210 manual can now be downloaded from JP's site: 
http://www.jptronics.org/OTHER/index.html

Scientific Radio Systems made good products and being in Rochester NY no 
doubt was cross-pollinated by Harris RF Comm engineers.   But it 
suffered with poor management for years,  the last being a group that 
owned several companies including Ithaca Gun Co.,  and went out of 
business when the CEO was convicted of embezzling money from the 
employees 401(k) account.  To his credit, he didn't pocket the  $45K but 
used it to shore up the failing company.

73, Bob W9RAN