[Milsurplus] RAS-4 documents

[Ray Fantini]

I have a RAS that I use as a monitor or any time I attempt to learn CW, also used t for a long time with my TBW back when I was running that. Huge receiver that fills an entire rack! Somewhat based on the HRO jr. but with a 175 kHz IF so it can accommodate a low frequency coil pack.  The IF is subject to strong image problems due to the low IF frequency and learning how to read the frequency can be a challenge but just like the HRO that its based on when working with a good set of tubes its noise flour is extremely low  and sensitivity very good for a receiver of that era. A properly working HRO still preforms tasks such as CW or AM reception that's equal to modern receivers, least that's been my experience. Forget it for side band and maybe above twenty meters its sensitivity drops but so what, never operate up there anyway. The original design did not include a noise limiter and static crashes can be a problem but there is a modification kit the replaces the original detector and its some form of weird impulse circuit or something that no one understands and was the subject of a thread a while back and if that's installed it solves that problem.
My receiver suffered a lot of leaky capacitors that had the result of killing the G2 voltage on several tube and worst of all swamped the AVC circuit so finally replaced all of the old wax capacitors. I have the original rack mount power supply and am amazed that after eighty five years the two electrolytics are still solid and don't leak. Don't know how they built them back then but they are still holding up. Also remember that the external speaker on that receiver is in the output tubes plate line between the plate and B+ so if you use the external speaker you need an external plate transformer, the headphone jack on the front of the receiver makes use of an internal transformer with a six hundred ohm output  but the speaker output on the back is at high level just like a lot of the older prewar radios.
BAMA has the manual free for download, it about 10 Mb so too big to attach, I am including a JPG that I did some time back that's useful for working on the radio. Don't get to caught up on what version of RAS it is because as far as I know the RAS is basically the same between all versions, lot like the TCS family of radios.

Ray F/KA3EKH



-----Original Message-----
From: milsurplus-bounces at mailman.qth.net <milsurplus-bounces at mailman.qth.net> On Behalf Of Bill Cromwell
Sent: Monday, October 27, 2025 8:20 AM
To: Milsurplus at mailman.qth.net
Subject: [Milsurplus] RAS-4 documents


My new RAS-4 is on the way here. I looked on BAMA for manuals but struck out. I am sure I will need the documents eventually even if the radio is plug n play right out of the box.

Can anybody tell me where to find the manuals or send a digital copy?

73,

Bill  KU8H
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