[R-390] Interesting AN/SRA-50 antenna multicoupler on the E place

[Bob Camp]

Hi,

I've bid on it each time it's been up. I have no idea how much the guy has
on the reserve.

There are various references on the net. It is definitely set up for
transmit / receive operation up into the 1K region. Obviously it's intended
for shipboard use. As I recall it or something very much like it is
responsible for the classic front end coil failures we see on the R-390A's.
There is a setting error you can make on it that basically puts the output
of the 1KW transmitter directly into the input of the receiver. The front
end coil for that frequency band more or less dies instantly in that case.

    Enjoy!

        Bob Camp
        KB8TQ

----- Original Message -----
From: "John KA1XC" <tetrode@worldnet.att.net>
To: "R-390 reflector" <r-390@mailman.qth.net>
Sent: Friday, March 01, 2002 11:23 PM
Subject: [R-390] Interesting AN/SRA-50 antenna multicoupler on the E place


> Item # 1336334840
> No connection to seller, just a FYI for the list so no flames!  :^)
>
> It's a BIG AN/SRA-50 receiver multicoupler which was reportedly used with
> 390s and may still be in use. It's been up several times without  meeting
> the reserve, but the pics are definitely worth a look.
>
> A friend of mine picked up a couple of the tuning units two Hosstrader, NH
> hamfests ago and I got to poke around inside them and take a look.
> Construction was classic high quality military, and the components look
like
> they are sized for transmitting rather than receiving.
>
> Referencing the top  picture, you can see two shielded RF compartments
each
> with an LC tank circuit. What is not readily apparent (but what I saw up
> close) is that the tank circuits are actually inductively coupled to each
> other through a small rectangular cut-out in the wall that separates the
two
> compartments. Cool!  One knob and gear train tunes the whole compartment.
>
> Mounted on the top side of the wall (in the pic), right between the coils,
> and on top of the cut-out is a piece of fiberglass board which was
partially
> covered with copper. It was mounted on a sliding mechanism that allowed it
> to moved up or down, thus changing it's position over the slot opening. My
> guess is that it served as an adjustable Faraday shield between the two
> tanks, or possibly as a means of adjusting the coupling between the two
> circuits. However, the copper section did not seem to be connected to
ground
> which I thought was strange.
>
> 73,
> John
>
>
>
>
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