[ARC5] BC-450 Control

[Mike Morrow]

Brian wrote:

> What he has available is a very good example of the BC-944,
> the near drop-in.equivalent of the C-38/ARC-5, except for
> the nomenclature plate.
>
> Cheers es 73 de Brian, VK2GCE.

Brian,

I don't have much hard information on the short-lived SCR-274-N VHF components, but I seem to recall that the BC-944 looked similar to the BC-450-A except that it had two sections with the usual controls and tuning dials for two MF/HF receivers plus one section for the BC-942 4-channel VHF receiver from which the R-28/ARC-5 developed.

If all that is true, then the BC-944 is nothing at all like the C-38/ARC-5 control box.  The left two-thirds of the C-38 have NO tuning dials or mode selectors.  The C-38 allows adjustment of RF gain with a thumb rotor pot and a switch which kills receiver RF gain completely to "turn the receiver off."  One such switch is for the installed R-25 to R-27 MF/HF receiver "C", plus another switch for the R-28 VHF receiver "A", plus another switch "B" that is unused.  There is one combined VOLUME control for those receivers.  These are the only receiver controls necessary, because the MF/HF receiver would be fixed-frequency lock-tuned and hard-wired for VOICE only.  Transmitter control C-30A has the VHF channel select switch.

The right third of the C-38 has the controls for the R-4*/ARR-2 VHF Homing receiver with mode, gain, pitch, and modulating frequency channel select.

All electrical connections to the C-38 are made through one large 18-pin connector instead of three smaller 8-pin connectors.  There is only one spline connection which is used for the R-4*.

The C-38 also has a microphone AF switch that is used in some systems with the AN/ART-13 transmitter.  The unused receiver "B" RF controls mentioned above is intended for some installations using the ARB receiver.

AFAIK, there is nothing even remotely similar to the C-38 in earlier command set systems.  The BC-944 would be of no value in a typical AN/ARC-5 and AN/ARR-2 installation.

Mike / KK5F

PS:  In an earlier post today I referred to "RAV CBY-46002".  That should have been "RAV CBY-46102".

>-----Original Message-----
>From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On
>Behalf Of Mike Morrow
>Sent: Thursday, 31 October 2019 1:32 PM
>To: arc5 at mailman.qth.net
>Subject: Re: [ARC5] BC-450 Control
>
>Phillip,
>
> If your AN/ARC-5 display is to be accurate, note that the AN/ARC-5 system does not use nor have an equivalent to the SCR-274-N BC-450-A.  (The closest thing would be three C-26/ARC-5 single receiver controls.)  A typical carrier-based aircraft's AN/ARC-5 three-receiver rack would use a C-38/ARC-5 control for the R-4*/ARR-2 VHF Homing receiver, R-25 to R-27/ARC-5 lock-tuned MF/HF Communications receiver, and the R-28/ARC-5 4-channel VHF Communications receiver in the MT-65/ARC-5 rack.
>
> The two-transmitter MT-71/ARC-5 rack would contain a T-18 to T-22/ARC-5 MF/HF transmitter and a T-23 or T-126/ARC-5 4-channel VHF transmitter.  The modulator would be a MD-7/ARC-5 and the control a C-30A/ARC-5.
>
>Typical AN/ARC-5 with AN/ARR-2 installations were quite a bit more capable and sophisticated (and interesting) than the simple ARA/ATA and SCR-274-N predecessors of just three years earlier.
>
>Mike / KK5F