[Milsurplus] Was speaking of GP-7 - now RU/GF style j-box

[Mike Morrow]

>Another possibility may be the SCR-AR-283.  The manual shows an RU/GF
>style j-box as "part of airplane, not furnished by Signal Corps".

The junction box (when the circuitry within has not been built into the
aircraft) for the later versions of the SCR-*-183 (including the AR and AS
models) is the TM-AH-172.  Though visually similar to the RU or RU/GF boxes,
it has significant differences and is not interchangeable.  It is only
available for 14 vdc systems...no equivalent junction box was provided for
the 28 vdc SCR-*-283 versions.

For that matter, there are major major differences in the junction box for
a liaison receiver version of the RU like the RU-18/19 and the junction box
for a command set version like the RU-16/GF-11.  The liaison receiver
JB accomodates one or two receivers and no transmitters.  The RU/GF JB
accomodates only one RU receiver and only one GF transmitter.

In typical USN liaison systems, such as a RU/GO or RU/GP, the only thing that
happens on transmit is the antenna is disconnected from the receiver input
and is connected to the transmitter output, and the receiver input is grounded.
This is all done by the antenna relay in the transmitter.  No receiver muting
occurs (as it does for the BC-348 in the SCR-287 or AN/ARC-8).  Thus, there
is nothing in a liaison receiver version of the RU that connects to the
associated transmitter except the antenna lead.  Nothing in the system
junction box connects to the associated transmitter.

I've got a TM-AH-172 and a TM-AF-172.  They can be a bit hard to find.
Fair Radio had some ten years ago.

I bought a new-in-unopened crate SCR-AS-183 ten years ago, and there was
no junction box included.  For that matter, there were no receiver coils
either.  Apparently, most AS models were used with AR system coils.  I
have located only one coil assembly for the AS receiver after a decade of
searching.

Mike / KK5F