[ARC5] Drift in ARC-5s - and other matters.

[Lenox Carruth]

 Kenneth G. Gordon wrote:


>On 8 Dec 2008 at 13:10, Bob Macklin wrote:

>> I have  not looked at an ARC-5/SCR-274 rig in over 40 years but I do
>> remember some about them.

>You might want refresh your memory by reading the manual here:

I did.  I also have the aircraft manuals for many WW-II aircraft that
clearly show the installations for the Command Sets and the Liaison Sets and
explain their use.

Refer to:  AN 16-30ARC5-2 and T.O. No. 08-10-50

For an excellent view of the installation and use of the radio equipment in
a World War II bomber see:

Service and Instruction Manual, Radio, B-24D Airplane published by
Consolidated Aircraft Corporation

><http://www.mines.uidaho.edu/~glowbugs/PDF%20files/ARC5/ARC
-5-man.PDF>

>> These units were designed for aircraft to aircraft and aircraft to
>> ground operation using VOICE. Not CW.

>Sorry. That is wrong. They were used very heavily on CW. The
>main use of voice with them was in fighter aircraft before the AAF
>switched to VHF.

Not true.  The Command Sets were primarily used on voice.  There was no cw
key provided with the exception of the one on top of the transmitter control
and it was frequently mounted in a position that would almost eliminate the
ability to send CW or MCW.  Both the transmitters and receivers were
equipped for VOICE, CW, and MCW.  The MCW was called TONE on the transmitter
control head.  The push-to-talk switch was typically mounted on the throttle
or the stick in single-engine planes or on the control wheel on multi-engine
aircraft.  Purists will note that the P-38 had a control wheel in which was
mounted the push-to-talk switch.

They were intended only for short range communication between aircraft and
ground and between aircraft, hence the name Command Set.  The Liaison Set
was used for long-distance communication and that was almost 100% CW.

>> They were also only intended fro
>> short range communication.

>Again, not necessarily so.

Yes. it was so.  The VHF Command Sets replaced the HF Command Sets and
performed exactly the same function.

>> I seem to remember these units having provision for MCW operation.

>No. None for transmitting.

Yes, the transmitters had a TONE position in which MCW was transmitted.  In
the MD-7/ARC-5 modulator the tone oscillator tube was a 12J5GT.  In the
BC-456-A, the tone oscillator was listed as a type VT-135 which is also a
12J5GT.


>Ken Gordon W7EKB




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