[Milsurplus] SC-901X questions

Tue Mar 27 09:29:29 EDT 2018

Turret style tuning by General Dynamics was the solution to the problem of filtering out unwanted harmonics and incidental products that were an issue in all the first generation synthesized radios that they designed and built. It’s a huge over complicated system but it works well. So well it found its way into several generations of radios like the R-1051 family, the URC-35 and URT-23 and a completely different radio the AN/GRC-106 that although it don’t look like any of the Navy gear is electronically almost identical.
The A2A4 RF amplifier assembly used in the 1051 is in a sense a thirty band tuned amplifier that dose a great job of attenuating any out of band products. In things like the T-827 exciter or the RT-618 transceiver it also scrubs the output of the RF Translator and removes all out of band products that are an issue with synthesized radios of that generation. Where others used lots of relays that required a complex control system or an automatic or manually tuned network the General Dynamics system required only a mechanical network as opposed to later transceivers that used a microprocessor to select the appropriate filters for proper operation.
Harris, Sunair and Mackay were heavily into the use of relays to select the appropriate filters to remove and block out of band products. Now decades past production we see that things like the relays in radios like the RF-350K are its weakest point and today are at a high rate of failure but the older design of the General Dynamics turret still is going strong at least in the radios that I am experienced with.
I had a 901 years ago and it had the rack mount kit attached and from what I was told it was produced epically for use in underground silos and always assumed that was its only role and as such may have no connection to its Navy cousin beyond the same connection that the GRC-106 has to the Navy. The common factor is General Dynamics and not the Navy.
It would be interesting to see a time line of when the following sets were deployed. Going to speculate that URC-35 (RT-618/AM-3007), R-1051 and URT-23 (T-827/AM-3924), AN/GRC-106 (RT-662/AM-3349) and where dose the SC-901 fit in that family tree. Think there is also something like a WRC-1 that is a R-1051/T-823 and AM-3007 that fits in there somewhere.
Going to post this over on the R-1051 list also to see if anyone can give a complete time line and if there are any other sets I am missing in the lineup.

Ray F/KA3EKH

From: milsurplus-bounces at mailman.qth.net [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Nick England
Sent: Tuesday, March 27, 2018 4:38 AM
To: Hubert Miller <Kargo_cult at msn.com>
Cc: milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] SC-901X questions

SC-908 amp Photo

https://m.ebay.fr/itm/Military-HF-SSB-linear-power-amplifier-1-5kW-SC-908A-excellent-8295A-tube-ham-/111647795170?_mwBanner=1

On Tue, Mar 27, 2018 at 10:34 AM Nick England <navy.radio at gmail.com<mailto:navy.radio at gmail.com>> wrote:
There was a matching 1kw SC-9?? amp using a PL-172. One shows up on eBay every now and then.

I suspect this was all a USN funded development effort. Air Force use was just incidental. The low power exciter design allowed flexibility as it did for TMC.

And commonality of modules for transceiver, receiver, and transmitter was a big plus. Navy versions were RT-618, R-1051, and T-827. Amps for 100w (AM-3007) and 1kw (AM-3924) output were used.

OT- Duck and cover was to protect kids from flying glass and debris. No use at ground zero but there would be huge areas getting shock wave damage. People nowadays laugh at CD, SAGE, etc. but remember this was just after a world war with 100 million dead and suddenly a single aircraft could destroy a city. The govt was rightfully extremely worried.
YMMV
Nick

On Tue, Mar 27, 2018 at 7:34 AM Hubert Miller <Kargo_cult at msn.com<mailto:Kargo_cult at msn.com>> wrote:
This doesn't address why a SSB exciter was built into its own package, when the power output
from it would not suffice for communication on its own. I didn't bring mine back with me from the
trip, but I don't recall rackmount ears on it either.  Maybe next time. I'm sure it will be super
interesting to pull the cover and see the insides.

Diving under a desk wouldn't protect you from a nuclear blast unless you were far enough that
the pressure wave was lessened at your location. Then it might help you ward off some flying
glass and other junk. But even if you were closer, too close to survive the initial effects, very few
people would just give up, say why even bother. That's not human nature.
-Hue

>CD was Civil Defense. Back when
the Nuclear Holocaust was just
around the corner.

Tons of that stuff sort of went away
and never heard from again.

As for the SC-901X, it was designed
to survive a Nuclear blast. People
really got paid big bucks back then
to think up these requirements.

I remember when schoolkids had to
crawl under their desks in the event
of a Nuclear attack. Like that would
help you survive a 20 Megaton blast.

73, Dick, W1KSZ

______________________________________________________________
Milsurplus mailing list
Home: http://mailman.qth.net/mailman/listinfo/milsurplus
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Milsurplus at mailman.qth.net<mailto:Milsurplus at mailman.qth.net>

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
--
Nick England K4NYW
www.navy-radio.com<http://www.navy-radio.com>
--
Nick England K4NYW
www.navy-radio.com<http://www.navy-radio.com>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/milsurplus/attachments/20180327/3a2c95cc/attachment-0001.html>