[ARC5] Re: SCR-274-N Transmitter Dial Accuracy

Mike Morrow kk5f at earthlink.net
Tue Jul 8 16:35:54 EDT 2008


I wrote:

> I'm not considering the SCR-274-N made by WE and others to be A.R.C.
> gear.

Michael wrote:

>Okay, here's where our points of view differ.  I look at the design
>source otherwise it gets confusing.  For example, Colonial built the
>SCR-522, SCR-274-N and ARC-3 (and probably other equipment) under
>subcontract so who gets credit for them?

In my view, I choose whoever made the majority of any particular item.

For ARA/ATA and AN/ARC-5, I'd say A.R.C. has the edge over S.C.

For SCR-274-N, W.E. has the lion share over anyone else.

>...a goodly number of the T-47As were made by Stewart-Warner
>(among others) yet I've never heard anyone call it anything but a
>Collins transmitter.

I would not.  I believe that Collins made fewer T-47A/ART-13 units than
Stewart-Warner.  In fact, I don't ever recall seeing a Collins T-47A.
(I like the T-47A better than any other model of the "Collins ART-13"
transmitters.)

>The ARR-1s and ARR-2s I have on hand here are split pretty evenly
>between WE and Zenith...

It appears to me from the ones I've seen that Zenith made more of the
AN/ARR-1 sets, while WE made more of the AN/ARR-2 sets.

I wrote:

> Once one removes the command set gear, what else did A.R.C. contribute?

Michael wrote:

>Wasn't this enough?  Every combatant that flew as well as a fat number
>of transports et al carried command equipment, whether it be HF or
>VHF...

That's the rub for A.R.C., because they built no successful VHF command
sets.  I don't wish to start up the HF vs. VHF command set use controversy,
but clearly, overall, VHF command sets won out over HF by war's end.  A.R.C.
played no part in the development of a usable war-time VHF set.  The
war could likely have been better prosecuted had no HF command set ever
been accepted by US forces during the war.

>... On the other hand, not all Navy and not that many USAAF
>aircraft carried the ZB or ARR-1 or the later ARR-2, and the SCR-274-N
>and ARC-5 VHF components weren't built in any huge quantities - 1000 &
>20,000 respectively.

I consider the SCR-274-N VHF components to have never really survived
the development phase.  I know of no edition of any SCR-274-N manual
(I've got four, from the first 1941 version, to thee last in 1956, IIRC)
that even hints of the VHF components, nor have I seen any other official
documentation.

>As a sidenote, my T-23 was built on a BC-950 chassis, complete with
>the hole for the 815(?) socket.

I recently traded off a R-28 that had an old-style channel selector and
a tube cover with a diagram showing tubes designated by Signal Corps "VT"
numbers and showing the dynamotor as a DM-32-A.  Very possibly, that unit
had once been a BC-942.

I wrote:

> The AN/ARC-39 seems to have been made in very small quantities.

Michael wrote:

>There were only 400 A.R.C.-built ones...

>Some, though not all, wound up in places like the P-3 where it was
>parked next to an ARC-94 and something VHF/UHF-ish.  The ARC-2, on the
>other hand, went with the ARC-38 (the AM version) in the P-2 and P-5.
>They also had something VHF/UHF-ish.

I would think that the AN/ARC-39 would be very unsatisfactory for use
in longe range Navy patrol aircraft.  I know some such aircraft in
the 1960s carried an AN/ARC-38A along with the AN/ARC-94 (Collins 618T).
I doubt there was much VHF command set gear on USN aircraft past the
1950s...the USN after all pioneered the use of the military UHF-AM band,
with the RT-58/ARC-12 that directly replaced the RT-18/ARC-1 using all
the mounting and control hardware of the AN/ARC-1, except antenna.  The
classic UHF-AM command set of all time IMO is the AN/ARC-27, which
replaced the AN/ARC-12.  I've been looking for a complete RT-58/ARC-12
for years.  I couldn't afford them when I was in high school in the 1960s,
when Fair Radio had them for sale.

I wrote:

> What part is played by A.R.C. type 12 components in your system?

Michael wrote:

>The system is built around the A.R.C. Type 12 C-40 control head,
>although mine's a Stratocon R-2001 which is functionally the same but
>made for panel installation in 1960.  Its a fairly conventional 3
>receiver (VHF, HF and LF/MF), 2 transmitter (VHF/HF) setup with the
>R-28 and R-23A/ARC-5 replaced by an A.R.C. R-19 and R-11 respectively.

Interesting.  Did it use a MT-7/ARR-2 rack for a MF/HF receiver,
and a MT-71 for a T-23 and some other MF/HF transmitter, thus requiring
a MD-7 and RE-2 in the system?  Sounds bizarre, when a T-11 or T-13
VHF transmitter could have beeen used for VHF.  None of my
A.R.C. Type 12 manuals show anything similar.

>There is also provision for an FM set ("like the SCR-619") but I
>doubt that particular set would have still been operational in 1960.

One of my A.R.C. Type 12 manuals shows a similar use of the SCR-619
(BC-1335), in a 24 vdc system with C-37 control box, R-11, R-19, and
two T-11 or -13 VHF transmitters.  A resistor is shown in the power
lead to the BC-1335, which normally only runs from 6 or 12 vdc.  I've
always wondered about the use of the BC-1335 in this function, because
although the BC-1335 is a neat little two-channel VHF-FM set, for
some unknown reason it has NO squelch circuit!  It wouldn't be fun
to listen to FM noise continuously.  

>It came out of the 1952 edition of AN 16-45-122 which is the manual
>for the Type 12 equipment.  It's not in the 1956 edition which, given
>when the control head was made, is interesting.

>While I didn't want to build a normal 3 Rx, 2 Tx, setup, this one
>appealed to me because it's different.

My favorite command set that I've assembled is a three-receiver (R-4,
R-26, R-28), two-transmitter (T-23, T-20) AN/ARC-5 and AN/ARR-2 system.

>The control head has a dial for the R-26 so that's why I selected 3105
>KCs.  (Reflective thought: wasn't that changed to 3110 KCs later?)

In the early 1950s the standard civil air-to-tower frequency changed
to 3023.5 kHz.  That frequency today is officially assigned for search
and rescue use.  I don't know why 3105 was changed, but 6210 kHz must have
been lost at the same time, since most of the simple transmitters just
doubled a 3105 crystal to get the 6210 frequency.  I don't know what
3105 kHz is assigned for today.

Old radios...gotta love 'em!

Mike / KK5F


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