[ARC5] ATA Transmitter Control Box

[Mike Morrow]

Robert wrote:

>All three of the standard MF/HF transmitter control boxes (NT-23243, BC-451-A 
>& C-30/ARC-5) are the same in this regard.  They all control up to four 
>transmitters.

Yes, there has never been a transmitter control box for these sets except one
capable of controlling four transmitters.

I suppose the AN/ARC-5 system has the greatest diversity in the sphere of
transmitter control boxes.  First there is the extremely rare (for good reason)
C-29/ARC-5 MF/HF transmitter control box, along with the (IMHO) rather stupidly
designed C-30/ARC-5 MF/HF/VHF "pushbutton" control box, followed by the final
and apparently most frequently used C-30A/ARC-5 MF/HF/VHF "selector switch"
control box.  The C-30 and C-30A could be utilized just as easily for systems
that did not use a VHF transmitter.  The C-30 is much more mechanically complex,
larger, heavier, and no doubt much more expensive than the C-29, so perhaps
that's why the C-29 MF/HF-only unit was made available.  But the later C-30A
is essentially the same size/weight as the C-29 with much greater versatility.
It controls up to four transmitters, one which *may* be a four-channel VHF
transmitter.  It can select the VHF channel of operation (including the VHF
receiver channel) even if a MF/HF transmitter is selected for operation.
The old C-30 box can not select a VHF receiver frequency without also
selecting the VHF transmitter for operation.  The C-30A does not require that
the VHF transmitter be in the rack postition designated as position 1, as
does the C-30.  One wonders why the complex but limited capability C-30
ever saw light of day.  The simple and capable C-30A would seem to have
been the most logical development from the C-29.  For some reason, most VHF
control box designs of WWII appear to be based on the British pushbutton
controller pattern such as is found on the BC-602 for the SCR-522-A.  The
C-118/ARC-3 is another complex pushbutton example, but soon the simple
selector switch control panel C-404A/A was available instead for the
AN/ARC-3. 

AN/ARC-5 systems with only one MF/HF transmitter (such as found on some
training or utility aircraft) would likely not even have a transmitter
control box.  The rack connections would be wired to make up the same 
connections that a control box on VOICE selected to transmitter 1 makes.
For these simple configurations, the *only* transmitter control is the
microphone PTT switch.

>AN/ARC-5 has a 4-receiver rack (MT-67/ARC-5) but no 4-receiver control
>box that I know of.

Sure you do, Robert.  The most common AN/ARC-5 receiver control box, the
C-38/ARC-5, has audio/sensitivity/volume controls (only) for the R-28/ARC-5
VHF receiver and up to two lock-tuned R-25/26/27 MF/HF receivers, plus all
operating controls for the R-4/ARR-2 VHF homing receiver.  Those would fill
up that rack of four.

>The ATA/ARA manual mentions that it is possible to set up a 4-transmitter 
>installation by modifying the second of two 2-transmitter racks.  In the
>AN/ARC-5 racks, there is provision for changing the channel number of any
>transmitter position without getting into the wiring box.  And AN/ARC-5
>included the 4-transmitter rack MT-75/ARC-5.

Plus, there is a rare junction box (J-34/ARC-5) which allows the MD-7/ARC-5
to service two racks of transmitters in conduit cabling systems.  Not even
this J-34 is required in open-wiring systems employing two transmitter racks.

73,
Mike / KK5F