[Milsurplus] ID an IFF (or possibly radar)

[Marty Reynolds]

> Every year or so I try to identify a unit that I have, mil-spec
> manufacture but no identifying plates:
>
> TX chain is pair of 8025's modulated by an 829B.
> RX chain is couple of acorn tubes, presumably RF + regenerative detector.
> There are a number of 6SK7, 6SN7, 6V6s and a few IF-type cans.
> Perhaps signal forming? No relays or anything that would be indicative
> of an IFF (in my limited understanding).
>
> It could perhaps also be an altimeter(?). Operating frequency would
> appear to be in the 100-300MHz range.
>

Ian I believe it's the BC-688/BC-689 pioneer radar altimiter pair by RCA. 
Called SCR-518  Had like-new examples I donated

Follow on was ingenious & long-used APN-1