[Milsurplus] [MMRCG] SR Systems SR-206

[mstangelo at comcast.net]

Sorry I'm late in replying but I was away.

I remember picking up some Scientific Radio Systems antenna couplers at a Hamfest years ago. They are model SC-610. They come in a waterproof fiberglass enclosure about 16x12x6 inches with a large ceramic insulator meant to feed a wire antenna. The circuit consists of switched fixed capacitors and a large air inductor. The circuitry is selected via ceramic switch sections controlled by a stepper motor. The control lines are accessed my a connector. It is designed for channelized operation because you have to install the appropriate capacitor and inductor tap for each channel.

Does anyone have a schematic or information on the protocol used to control the stepper motor? I'd like to get it working.

I asked about these radios years ago. I heard from a person in Switzerland who worked for the U.N. He mentioned that they used the SRS radios in third world countries but the radios were replaced with ICOM radios. 

Mike N2MS

> On 09/18/2023 1:21 PM EDT Robert Nickels <ranickels at gmail.com> wrote:
> 
>  
> 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