[ARC5] Arc-5 transmitter rack plugs...Some info on INTERCHANGEABILITY

[Mike Morrow]

I wrote:

> Different connectors are used throughout the AN/ARC-5 transmitter system,
> because the ONLY TWO COMPONENTS in the AN/ARC-5 transmitter system that are
> electrically interchaneable with equivalent components in the ATA or SCR-274-N
> system are the DYNAMOTOR and the ANTENNA RELAY.  This is pointed out in many
> places, such as the article at http://en.wikipedia.org/wiki/AN/ARC-5 .

It may be worthwhile mentioning a little more about what can and can not be
interchanged between these Type K "command set" radio systems:

The first version of this system is the US Navy ARA five-receiver (CBY/CCT-
46129, -46145, -46104, -46105, -46106) and ATA five-transmitter (CBY/CCT-
52232, -52208, -52209, -52210, 52211) system.  It appeared in 1940.  It
uses low impedance AF circuits in the receivers and the modulator (CBY/CCT-
50083).

The second version of this system is the USAAF SCR-274-N three-receiver
(BC-453-A/B, BC-454-A/B, BC-455-A/B) and three-transmitter system (BC-457-A,
-458-A, -459-A) that was soon expanded with receiver (BC-946-B) and transmitter
BC-696-A).  It appeared in 1941.  Electrically it is identical to the USN's
ARA/ATA system, EXCEPT FOR AF IMPEDANCE.  The earliest versions used high
impedance AF in the receivers and modulator (BC-456-A), but soon versions (B/E)
were produced that could be wired for either low or high impedance AF.  Because
of these minor differences exist, all equivalent ARA/ATA and SCR-274-N components
are otherwise completely interchangeable.

The third version of this system is the USN's improved ARA/ATA:  The AN/ARC-5
MF/HF receivers (R-23* through -27), one VHF receiver (R-28), five MF/HF
transmitters (T-18 through T-22), two VHF transmitters (T-23, -126), and three
special purpose MF transmitters (T-15 to -17) began appearing in 1943.  The
receivers were improved with AGC.  The R-23* and 24 navigation receivers
have special AF output for the MX-19/ARC-5 audio adapter panel for the AN/ARN-9
Air-Track ILS system (abandoned in favor of USAAF SCS-51 ILS), and they are the
**ONLY** "Type K command-set" receivers with loop terminals and switch. The
R-25 to -27 receivers incorporated HF stability modifications to enable
pre-set lock-tuned capability.  Regardless of the expanded capabilities
of the AN/ARC-5 receiver system compared to the earlier systems, components
are still mechanically and electrically interchangeable with earlier equivalent
components.  That is NOT TRUE of the AN/ARC-5 transmitter components, NONE OF
WHICH ARE INTERCHANGEABLE with ATA or SCR-274-N equivalent components except
the antenna relay (CBY/CCT-29125, BC-442A/AM) and the dynamotor (CBY-CCT-
21626, DM-33-A).  Most of the connectors used in the AN/ARC-5 transmitter
system system were deliberately made different in order to prevent a sailor
from trying to connect an ATA component into an AN/ARC-5 transmitter system,
or the reverse. (The ARA/ATA and the AN/ARC-5 were in simultaneous use in
the USN after the AN/ARC-5 system appeared in 1943.)

So...in summary:

1. Equivalent components of the ARA, SCR-274-N, and AN/ARC-5 receiver systems
are interchangeable, although not necessarily with equivalent capability.
2. Equivalent components of the ARA/ATA and SCR-274-N transmitter systems
are interchangeable.
3. ONLY the DYNAMOTOR and the ANTENNA RELAY of the AN/ARC-5 transmitter
system are electrically interchangeable with equivalent ATA and SCR-274-N
components.

Mike / KK5F