Scott SLRM National Radio R-302/URE-22 Connection

[Chris Bowne]

Hello all... I posted on that above subject here a few years ago regarding a very unusual National receiver I saw at a Nearfest NH hammer which looked like a Scott SLRM that had been converted to miniature tubes and had different power supply components. I recently came across what I believe I saw at Nearfest on Nick England, K4NYW’s Navy Radio web site. It was a National R-302/URR-22. Nick has info that National was awarded a contract to build modified REE receivers in 1949. REE was the Navy model number for the Scott SLRM Marine Receiver. From review of the URR-22 manual on Nick’s Navy Radio web site, the major modifications included replacement of the SLRMs AC/DC mains power supply with an AC only transformer type supply, replacement of octal tubes with miniature 6.3 volt filament tubes, the addition of a buffer amplifier stage to then BFO oscillator output, and incorporation of an AGC amplifier tube. The sets appeared to have used the original SLRM chassis, but was repackaged with a new higher front panel and larger cabinet. A dial lamp dimmer control and line level output controls were added to the front panel, and appear to be the main reason for the new higher front panel.

What Nick did not have info on was whether of not National modified existing complete Scott manufactured SLRM sets or built new ones from scratch using existing components either purchased from Scott or supplied from the Navy, or new parts purchased from the original suppliers. The set I saw would indicate that existing complete SLRMs were reworked, because there is evidence that the chassis have filler plates added over or under the chassis holes for the original octal tube sockets for mounting of the miniature tube sockets.

Does anyone have any more information on the SLRM/ National R-302/URR-22 connection?

Chris AJ1G Stonington CT
Scott SLRM S/N 1841

[Michael Lawton]

Actually, the AC/DC power supply of the original SLRM may well have been a requirement of the original WW2 order. At that time 125 V DC was used on some ships, especially merchant vessels,  rather than AC, being considered safer. In fact, even some parts of New York City still had DC electric service from the old Edison days into the late 1940s, my parents remembered those days. This was one reason so many manufacturers made AC/DC sets in that period. Later on, when the order was for Navy ships only, which had 120V AC as a standard, there was no reason for making the sets AC/DC, and several reasons for not doing so.

[Kent King]

Chris -

If it isn't too much trouble, I would love to get scans of the correspondence you have on the set. There is very little material in the time period, every little bit I can add to the archives would be fantastic. Your notes on the sets' limitations is dead on. The SLRM sets are adequate, but not a super performer. I sure enjoyed reading this and look forward to anything you might be able to send. 

My email is: [e-mail]

Kent

[Chris Bowne]

Thanks for the reply Kent. It appears that the Navy liked the SLRM,REE but wanted to Make some improvements for the “next generation” of shipboard super low radiation entertainment/backup communications receivers. Not clear if the recommended design changes came from Scott or another manufacturer such as National, or the Navy itself, but the two major ones, going to an AC only transformer type power supply and adding a buffer amplifier for the BFO certainly addressed the two major shortcomings of the SLRM. The transformer less AC/DC power scheme of the SLRM must have come from a requirement to allow the sets use on older merchant ships in convoys with DC receptacle power, perhaps the Liberty ships may have had such receptacle power. Virtually all of the problems I’ve had over the years with my SLRM 1841 have been with the power supply, especially the sets propensity to blow the No. 47 main tuning dial light build, which when it fixes, also kills reception. The bulb is powered Off of a voltage divider powered off the B plus. I’ve lost count of how many No.47 failures Ive had over the years. The bulb recieves a surge in current at set power up as the power supply filter caps charge up. WRT the BFO, the SLRM original design used a grounded plate Hartley circuit, but curiously, ther was no coupling of the. BFO output to either the detector or last IF stage, resulting in very weak BFO injection, which causes strong CW or SSB signals to overload the detector and can’t be properly demodulated. Perhaps that was a design compromise to allow the set to meet the Navy incidental radiation specs imposed on shipboard receivers, however, other Scott SLR sets such as the SLR-12B/RCH have very robust BFO injection and are very good CW/SSB performers.

Yes, I suspect that there were a lot of SLRM sets and components left at the end of the war. My S/N 1841 was bought from the Scott Manhattan NYC showroom by my mother’s uncle in September 1945 within 2 weeks of VJ Day for $250.00, a fairly hefty price for a radio in those days. My great-uncle purchased it as a replacement for a pre-ear Scott console receiver, and never was very happy with its performance. Correspondence he had with Scott Manhattan on it indicated he probably had issues with the pilot light related failures, and it obviously was no where near the
Big consoles in terms of audio quality. I’ve had it since I was 12, 56 years ago, it was t working when it was given to me, one of two large ballast resistors in the series string AC/DC tube filament strings was burned out. It’s still going strong, but I keep a good inventory of spare pilot bulbs around!

There eventually was a reduced cost version of the R-302/URR-22 called the R-892/URR-44 produced in the late 50s through early 60s, which was essentially the R-302 without the BFO and manual RF gain control. From illustrations in its tech manual, it still was using the same chassis and RF and IF components of the SLRM. They apparently were even specified for Installation on rhe SSN637 Class nuclear attack submarines, the last or which were delivered in the early 70s.

[Kent King]

Chris -

I have nothing to add to what you've posted. I do know that other companies built Scott models, but I've never heard of one being altered this much. Conversely, Scott labs built some other radios too (RCA specifically) during the war, but again, not modified. Once the military accepted a set design, other companies could build them but the design did not change. 

I do know that Scott had a metric crap ton of SLRM sets at all phases of the pipeline when the war ended. I could see them making National a very sweet deal on the surplus chassis. I have no information on how the company disposed of these, so this sort of arrangement is plausible. 

The latter half of 1945 and all of 1946 is only lightly documented. After Scott's departure in July 45, we don't know much except for the introduction of the 800B in Jan 46. I'll go back through my documentation and search on "National" to see if I can locate any connections. 

Thanks for this!!

Kent