[Milsurplus] ARC-38 control head connectors

[Mike Morrow]

>The heads for the ARC-38 and 38A are almost identical. The only difference
>I have found is the sticker that's placed over the mode control for SSB and
>a couple jumpers on the back of the control are changed.

I'm not sure what jumpers you refer.  The maintenance manual for the
AN/ARC-38 and -38A (NAVWEPS 16-30ARC38-502, 15OCT71) shows a wiring diagram of
altered wiring on one wafer of the mode switch, and then goes on to list 
"replacement of S2404A by a new switch wafer" as part of the modification
of the C-1398/ARC-38 mode switch to the C-3428/ARC-38A.  No schematic of the
C-3428 is provided.  It's that "new wafer" on the mode switch whose wiring is
not shown that seems to make converting the C-3428 back to the C-1398 problematic.
I believe that the rotor wafer on S2404A was changed, not any wiring at S2404A. 

Jack Antonio has experience using the C-3428 with an RT-311/ARC-38.  IIRC,
it works (mostly).

>Question: I have only seen couple 38A transceivers and heads but was there
>any ARC-38A that were produced as a 38A or are all 38A transceivers and heads
>re worked ARC-38 sets?

All the AN/ARC-38A sets were converted from old AN/ARC-38 sets.  Collins made the
AM RT-311/ARC-38 beginning around 1955, and RCA converted most of them to the USB
RT-594/ARC-38A beginning in 1961.  It carried RCA part number 8314517-501, on
USN Contract NOw 61-0729-r.  It makes sense that the Collins logos would be painted
on what is now an RCA product.

I guess RCA developed such AM-to-USB conversion expertise when they created
the conversion process to turn the USAF's RCA-built AM RT-128A/ARC-21 into the
RCA USB RT-400/ARC-65 in the late 1950s.  Unlike the AN/ARC-38A, new AN/ARC-65
units were also made that had never been the earlier AN/ARC-21.

It wouldn't have made a lot of sense for the USN to order "new" AN/ARC-38A sets.
The AN/ARC-38A was a sort of stop-gap USB set from the early 1960s.  By the late
1950s the most-excellent Collins 618T-series was appearing, which the USN adopted
as the AN/ARC-94 (618T-2) and the Army as the AN/ARC-102 (618T-3) in the early 1960s.
Many USN patrol aircraft of that era, which generally carried two AN/ARC-38A sets,
by the mid-1960s still retained one AN/ARC-38A (with AN/ARR-41) and one new AN/ARC-94.
(The AN/ARR-41 auxilary receiver was almost invariably installed with its companion
AN/ARC-38 or -38A, so anyone attempting to reproduce an AN/ARC-38/38A installation
should also consider the AN/ARR-41 as an integral part of the complete installation.
The CU-351/AR antenna tuner is also an integral part of the system.)

>One last interesting note is that when the radios were converted to "A" sets they
>stenciled on every module in the radio "modified for SSB" including things like
>the receiver audio amplifier, relay and servo amplifiers although in all three
>radios there is no difference in any of them.

I've got three RT-594/ARC-38A units.  Only the modules that were actually modified
are so marked on the two that I've spent some time examining.

Mike / KK5F