[ARC5] VHF AN/ARC-5 more small details

[David Stinson]

I'd love to see a photo of this rack, Mike.
The AN/ARC-5 VHF sets started out life as Army
SCR-274N sets, built on order number 2808-WF-42.
Western Electric made the sets,
Eastman Kodak made the control boxes.
An estimated 1000 sets were built under this order.
The most interesting thing about them was the modulator
circuit in the BC-950 transmitter.  The BC-456 has
too much "umph" for the VHF set, so it bypassed
the 274N modulator in favor of its own built-in
one, which used an 815 in push-pull.

The Army didn't buy the set in quantity, since
they were still bowing and scraping to all things
British, favoring the lumpen SCR-522.  If W.E.
had had the good sense to use the same crystals
as the cranky 522, they might have been successful
in selling it.  But they brought a set to the table
that required not one, but two new types of crystal
at a time when crystal manufacture was in critical
trouble;  bad idea.  The Navy, however,
was taken with the set, and wanted it incorporated
in the upcoming joint nomenclatured AN/ARC-5.

The Navy snookered the Army into doing the rework
of the sets under order #7461-WF-43.
You don't find many of the SCR-274N VHF sets
because the ones that were not actually issued
got reworked.
They saved some money on the design by tossing
the 815 and swamping the output of the MD-7
plate modulator when one switches to the VHF set.
They also redesigned the receiver mechanicals for
later production.
The rest of the work was just a matter of swapping
nomen plates.  If you check the ARC-5 VHF manual,
you will find and "early" receiver and a "late"
receiver.  The "early" receivers are the scarce
SCR-274N versions.
If you have an early model T-23, open it up and look
on the chassis.  You will find the hole for the 815
socket, usually filled with a hole plug.
If you have one of the really early sets that was
reworked, you can find scratches around the socket
where the screws were pulled out; I have one of them.
I know CBY got in on building some control boxes
under the Army order, but I didn't know about the racks.
73 Dave AB5S


Mike Morrow wrote:

> The contract numbers on the AN/ARC-5 VHF components that I've seen all have
> Army-type order numbers of 7461-WF-43 on them.  I have a two-transmitter
> rack MT-71/ARC-5 with that same order number on a black and silver paint
> phenolic screw-held name plate just like those on almost all the VHF
> components made by Western Electric.  Yet it has "CBY" on the plate, so it
> must be A.R.C. made.  It surprised me to find an AN/ARC-5 rack that didn't
> have a familiar rivet-held metal with blue paint name plate, and that A.R.C.
> made components on the 7461-WF-43 order number.
> 
> Isn't it odd for a set which seems to have been predominantly a USN-utilized
> set to have an Army-type order number on it, even in light of the VHF
> components being a direct descendent of Western Electric's VHF SCR-274-N?
> For that matter, what about all those R-1/ARR-1 receivers that have
> Army-type order numbers on them, but also USN anchor ink stamps on the
> paint?
> 
> Best regards,
> Mike / KK5F
> 
> 
> 
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