[ARC5] ARA, SCR-274-N, AN/ARC-5 Remote Control Box Dials - Questions

[Mike Hanz]

On 6/22/2011 5:18 PM, Mike Morrow wrote:
> Mike wrote:
>> I went out and took a couple of photos of the ones I have, Mike, and
>> it's a mixed bag.  Attached are two photos of the dials, front and
>> back.  The rear view is simply the front view with each dial reversed in
>> position.  The one on the upper right is for the BC-453, and is yet
>> another type that is commonly encountered - made of black Bakelite
>> rather than aluminum.  You can see that the two right hand dials are
>> both marked C-****, while the rest are all D-****.  Whether that
>> signifies 274N or not, I do not know.
> I suppose that the lower right .52 to 1.5 MC dial is the rare SCR-274-N MC-415 dial,
> or much less likely, an original early-ARA #6052 dial.  It's the first
> one I've ever seen.

I have no clue.  The center two in the photos are from ARA's (if I 
recall correctly), while the left hand pair are from ARC-5 sets.  There 
are subtle differences that are apparent with study, but without 
documentation, I'm not sure they are worth more than brief speculation.

> I also have never come across a bakelite dial.

I think I have encountered almost as many of those as the aluminum sort, 
for some reason.  Geographic distribution, perhaps...

> Those numbers like "D 5611" don't correlate to any part or drawing number
> that I've ever seen, but the four digits are consistent for each dial type.

Yes, they are consistent (thankfully) :-) , and they do correspond to 
some ARC contract drawing listings I have here.

> There doesn't seem to be a correlation that can be made to the letter
> in front of the four-digit number stamped on back.  Even the small-font
> dials of the SCR-274-N MC-213 and MC-214 have the same combination as
> the large-font dials of the late-ARA and AN/ARC-5.

I suspect that Mssr. Tauson's speculation about progressive replacement 
without nomenclature changes is pretty close to reality.  I mean, if you 
think about it, they all do the job - it isn't like a complex interface 
specification.

> The MC-415 is interesting.  I've had two NIB BC-946-B BCB receivers in
> past 15 years, made by Colonial.  They both came out of the box with the
> FT-310-A power adapter (for the associated AN/ARR-1) and a small instruction
> book.  It was surprising to me that there was no MC-415 dial included for
> the associated BC-450-A.  I wonder where the technicians got one for those
> rare USAAF uses of the AN/ARR-1 with the SCR-274-N.  I suppose they could
> leave the dial for the displaced BC-453-B on the BC-450-A and mark it to show
> the pilot where to find the modulating frequency of the YE/YG homing beacon
> of interest.  But who knows.  I think most of the AN/ARR-1 sets that were
> actually installed in USAAF service were like the B-29 installations
> which used the AN/ARN-7 ADF set to process the output of the AN/ARR-1.

Very likely...

73,
Mike