[Milsurplus] Post-WWII Aircraft Radio

[Mike Morrow]

Michael wrote:

> My Navy-converted BC-348-Q suggests they did do something with them beyond
> the original intent but I haven't a clue what.

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.

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.

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.

I wrote:

>> In fact, it seems that frequencies below 9050 kHz were not of great
>> interest for aircraft communications

Michael wrote:

> I'm assuming you mean "above."  :-)

Yes...just an obvious simple spelling error! :-)

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. :-(

> Civilians also expanded with equipment like the 618S and 618T radios which
> begot the AN/ARC-38(A), which was channelized rather than crystal controlled
> like the civilian version

The 618S-1 was perhaps just a little before the AN/ARC-38.  Both of these mid-1950s
sets share similar design and internal modules except that the 618S-1 has a crystal
oscillator module with 144 crystals, while in the same space the RT-311/ARC-38
has a Stabilzed Master Oscillator (SMO) that can generate operating frequencies
at either 1.0 or 0.5 kHz intervals, depending on the frequency.  Frequency is
entered as a alphanumeric code on thumb wheels, or yet another different set of
codes on the channel memory drum.  In spite of what one reads on the internet,
there was no exact civilian version of the RT-311/ARC-38.  That rumor seems to 
arise from the 618S-1/MC, which has a SMO that is controlled by the CPC-1 control
panel.  But here too, the frequency is dialed in on the CPC-1 as a set of ALPHA-only
characters.  None of that was too good for human factoring, and some have speculated
that it had a security basis.  I think it was just due to the limitations of the
electro-mechanical technology that Collins was using at the time.

I believe that the 1950 RCA RT-128A/ARC-21 is the first military (and maybe civilian)
airborne HF set that had direct dial-in numerical frequency entry.  That was followed
in the late 1950s by the USB version RT-400/ARC-65, and the USB/LSB/ISB Collins
AN/ARC-58.  Externally the RT-400 looks just like the RT-128A (18-inch, 145 lb,
pressurized drum) and most RT-128As appear to have been converted to RT-400.  That
may be why RT-128A/ARC-21 units are rare.  All these were USAF sets.  During the
1950s the USAF also bought many 618S-1 crystal-controlled sets without adoption
of JAN nomenclature.  These will have a little "U.S." on the name plate.  There
were also many purchases of the AN/ARC-59 (RT-380/AR, military version of the
Collins 18S-4 crystal-controlled AM set).  It is likely that the USN bought some
AN/ARC-59 sets too.

The USN used their AM Collins AN/ARC-38 until RCA got the contract to modify many
of those sets to USB...so thus appeared the RT-594/ARC-38A Collins/RCA HF set,
every one a former RT-311.  Apparently RCA capitalized on their expertise developed
converting the AN/ARC-21 to the AN/ARC-65.  Conversions took place beginning around
1961.

In the very late-1950s, the finest (IMO) and longest-serving airborne HF set of all
time appeared, the Collin 618T series.  It has direct frequency entry, of course, and
USB/LSB/AME/CW, 400 watts PEP.  It appeared in many civilian and military models, two
of the most common being the AN/ARC-94 (618T-2) and AN/ARC-102 (618T-3).  It wouldn't
surprise me to find a few 618T sets still flying, more than a half-century after
introduction.  

That's as recent as my aircraft HF radio interests go.  All the later stuff is too
much solid state, too much microprocessor oriented.

I wrote:

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

Mike / KK5F