[Milsurplus] Post-WWII Aircraft Radio

[Kludge]

-----Original Message-----
From: milsurplus-bounces at mailman.qth.net
[mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Mike Morrow
> I have a BC-348 (Q-model, IIRC) that has a small box over the original
antenna
> post with a SO-239 connector on it.  This BC-348 also has a Navy decal,
though
> I can't remember exactly what's on the decal.

This is the same as mine.  Once I have wheels again and can spend much time
at my storage units, I'll get it out and photograph it.  (This will also be
when I do a complete inventory of ARC equipment which should be
entertaining.)

>> I wrote of the BC-348:
>> ...other than not having remote tuning capability it's a good candidate
as
>> the best airborne communications receiver in one box in the world until
just
>> after WWII!  
>>Michael wrote:
>> Even without remote control, it was.  
> There's no argument from me, though one can understand why an ARB
> or R-26/ARC-5 with C-131/AR would serve better some USN applications
> where the transmitter and receiver are remote from the crew.

And, of course, I can't find my pics of the later TBF/TBM cockpit & radio
position.  These were aircraft equipped with the ATC and included at least
one with an R-26 and Yardeny controller sitting next to an ARB and another
with the Yardeny-equipped R-26 & R-27.  (I think the AN/ARR-2 in it also had
the motor driven tuning which would be pretty cool if my memory's right.)
What I don't remember at all is where the control heads were.

> The amazing thing about the BC-224/348 series is that the first model
> appeared in 1936 or 1937.  (I believe I have a manual for the BC-224-A
> with a 1936 date on it.)  A few descendants were still flying for the
> USAF in the early 1970s.

Just goes to show that a good design just keeps on keepin' on.  :-)

> I've found that I can read what I've written five times before posting and
> still miss unintended errors of fact, grammar, spelling...or all three.
:-(

I can't think of anyone here who hasn't managed at least one of them a time
or three.  It's all part of being human.  :-)

> The 618S-1 was perhaps just a little before the AN/ARC-38.  

Okay, let's see if I can pull this off without getting trounced too badly.
Any errors are due to memory failure, psychotropic meds or the reasons for
them.  :-D

Prior to WW II, Collins had a couple of 10 channel autotune aircraft
transmitters.  They were crystal controlled but had a tuning mechanism kind
of like the ATC, and they were the progenitors to that radio.  At this point
I'm a little hazy since I've read two different accounts of how Collins and
the Navy got together on this.  One is that it was a competitive bid and
Collins won with their first contracts let in 1942.  If so then who were the
other bidders and why did it take two years to get the first contract out
the door since they had the ATC - or at least prototypes - in 1940 as you
said?  The other is that Collins built the ATC without a contract or much of
anything else, as they have a few times in their history, then presented it
to the Navy (and maybe the Army) in sort of a "Here's a shiny new
transmitter to replace those 800 cycle clunkers you've got now, and, hey, it
does really cool tricks.  Watch this!" approach.  Okay, maybe not worded
like that but that was the idea.  

After the war (1946), Collins went back to crystal control with the 18S.
This was a neat package about the size of an ATC but containing a 10
channel, 20 frequency 2-18 MC transmitter-receiver, the transmitter portion
bearing an uncanny resemblance to the ATC.  If you think "AN/ART-13B with
the CTA-D oscillator unit installed", you'd be about right.  Each channel
had two possible frequencies with the pair no more than 2% (of the lower
one?) apart.  The receiver was a fairly straight forward superhet that ran
on 24v for the B+ and bore a kind of family resemblance to the TCS receiver.
(I'm doing this from memory since I haven't had the manual for one for a
while.  I need to find one to get the schematics, parts lists and the coil
information so I can get mine running on 160-20m AM/CW.)  

The Air Force or the Navy - or maybe both - liked this rig so adapted it as
the RT-380/AR (p/o AN/ARC-59) as a replacement for the AN/ART-13 & variants
with whatever receiver they were being used with at the time.  I've seen
pictures of the military versions but never actually saw one in person.  The
one I have now and the one I had back in Pittsburgh were/are both 18S-4s,
which really makes no difference in the end.

Shortly afterward in the 50s, Collins brought out the 618S-1 - 144 channels,
crystal controlled, 2-25 MC range, as you said.  While the Air Force was
making nice with RCA, the Navy got interested in the new Collins rig and
ordered a few as built to "road test" them.  They liked it but wanted
greater frequency agility which lead to the SMO-equipped RT-311/ARC-38.
(Collins also designed the R-648/ARR-41 to go with it although I don't know
how that came about.)  I have one of the main control boxes for one
(actually for the RT-594/ARC-38A) and if you're at a loss for passwords,
just turn to any page in it to get a nice bunch of randomness.  AM didn't
stick around long and the Navy contracted with RCA to convert the RT-311s it
had on hand to USB, the result being the RT-594/ARC-38A.  From what I
remember from my manuals, the 618S-1/MC was still crystal controlled but
also had the RCA conversion done to it for the civilian market to replace
the 618S-1.  

A new decade brought a new radio, this time the 618T.  Covering 2-30 MC in 1
KC steps (At least one version - -2B? - has a .5 KC step size.), it puts out
400w on USB, LSB, AM Compatible, CW and probably a few modes no one ever
heard of before.  The -1 (a kind of "crippled" version of the -2 intended
for retrofits only) and -2 run on 115vac, 400 cycle, 3 phase while the -3
runs on 28vdc at around 30-40 amps plus around an amp worth of 115vac 400
cycle single phase.  Several military versions exist as mentioned but also
including the AN/ARC-105 which is a pressurized model.  While newer
equipment has since come out, the 618T is still in service here 'n there and
probably will remain so for quite a while.

I'm sure I've flubbed a few things and missed others but that should be a
decent start for discussion.  :-D

>>> A 28 MHz aircraft transmitter in 1938 was an achievement.
>>Michael wrote:
>>That's a resounding understatement.  :-)
>There's another error.  I was referring to the GO-4, so I should have said
"26.5 MHz".

Klose enuf fer gummint werk.  ;-)

>Still, quite an achievement.  (And I can appreciate Ray's skepticism about
performance.)

Which raises the question anyway of how they tuned them.  The LM only went
to 20 MC according to specs although I know for certain it was useful to at
least 30 MC.  

By the way, the GH and GI aircraft transmitter/receivers were rather
interesting.  The transmitters went to 13.575 MC but the receivers continued
up to 18 MC.  I have no clue how many were actually built and used but they
are mentioned in one of the documents on Mike H's site and appear as
evidence that the Navy was clearly interested in frequencies that high in
the mid 30s.  

Best regards,
 
Michael, WH7HG ex-K3MXO, ex-KN3MXO, WPE3ARS, BL01xh ex-Mensa A&P PP BGI 
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