[ARC5] arc-5 BCB RX seen

[Mike Morrow]

I wrote:

>I suspect that the old tale about those power adapters being
>used for the LM frequency meter is mostly just supposition.

John wrote:

>I suppose your reasoning is that since the receivers would be
>netted before takeoff, precision resetting to a different
>frequency in flight was an uncommon occurrence in actual use.
>(hence fixed tuned receivers)

And Robert wrote:

>I expect that the LM was more likely used for checking or re-setting
>the Liaison Set...why build LM models capable of operating from an
>external supply or 12/14 and 200/260, 24/28 and 200/260 or finally
>12/14-24/28 and 180/260-260/475?  Plus the obvious fact that the LM's
>DC power cord plugs directly into the accessory connector on the ARA,
>ARB and RU juction box.

And Mike wrote:

>I dunno, Mike.  See http://aafradio.org/sidebar/C100-066.JPG for one 
>example, this in a PB4Y-2.  The wiring diagram shows it going to the LM 
>in the bottom photo at http://aafradio.org/flightdeck/RAX-1.htm.  Yup, 
>you could have also plugged it into the ARB, but the ARA was closer to 
>the Adel clamp attachments on the wall of the aircraft.  Stranger 
>decisions have been made in the fabrication process...
>
>I've learned a long time ago never to say never... :-)

Hi all,

I didn't mean to say that the LM never drew power from some convenient source, nor that the source wasn't sometimes an ARA or AN/ARC-5 receiver.  I have a couple of well-used R-26/ARC-5 units that have the MX-20/ARC-5 power adapter installed, doubtless for just the use that you all state.

What I intended to state was that the ARA or AN/ARC-5 command set wasn't required to be calibrated in flight by an LM, and that the only receivers issued with the power adapter were those intended to mate to the VHF homing adapter and not the LM.

The USN's other radio sets, like the RU/GF, the RU/GP, the RU/GO, the ARB/ATB, the ATD, and the RAX-1 sets had nothing in the form of internal accurate frequency setting capability.  A LM connected somewhere would have been vital, even for in-flight use, as Robert mentions in reference to setting the liason gear, so it is no surprise to see power connections made available at the RU junction box or ARB for LM (and other) use.  All these sets required trained radio operator intervention in normal use, except perhaps the RU/GF due to the very broad RU.  I am much less convinced that the ARA/ATA and the AN/ARC-5 would have any need for in-flight frequency adjustment other than at the ARA receiver control box.  Especially not the AN/ARC-5, with stabilized fixed-tuned communication receivers.  If a LM was connected to either of these sets, it likely was so that the LM could be used for gear other than for these sets.

Mike, those PB4Y-2 photos are very interesting.  In the first, there is an ARB/ATB installed, and two AN/ARC-5 receivers installed, both of which appear to have the MX-20 adapter.  I say it's AN/ARC-5 and not ARA, because the receiver to the right has loop antenna posts.  These were only on the R-23 and R-24/ARC-5 and the CBY-46102 and CBY-46103 RAV navigation receivers.  There's also a small frequency setting plate and the circle-S stamp on the other receiver which only the stabilized AN/ARC-5 communications receivers had.  The second photo shows what looks like the C-26/ARC-5 single receiver control box outboard the ATC.  I don't think there was a single-receiver control box in the ARA system.

I'm surprised to see the LM figure so prominently with the ATC/RAX-1.  The internal CFI of the ATC should have allowed frequency setting of the ATC and the RAX-1 to sufficient accuracy without any external CFI.  Maybe it was actually used for the nearby ARB/ATB.

All in all, it's a very interesting installation of ARB/ATB, ATC/RAX-1, and AN/ARC-5 receiver sets.

The SCR-274-N utilized the BC-946-B with FT-310-A power adapter.  I'm pretty sure that other SCR-274-N receivers seldom had the FT-310-A installed.  The battery-powered SCR-211 frequency meter didn't need power from installed gear, and the SCR-274-N didn't require in-flight frequency adjustment outside those performed by the pilot at the BC-450-A receiver control box.

Mike / KK5F