[ARC5] My "ARC-5" Impressions (long)

[Mike Morrow]

It was asked:

>> what in your opinion are the most impressive or noteworthy aspects of
>> the ARC-5 series design?

Hi Dave,

I think we may have some differing opinions on details, but not in our
admiration of these sets.  But...

I think what is impressive about the A.R.C. effort was how quickly the
1938 state-of-the-art Type K designs became woefully obsolete in less
than seven years.  The AN/ARC-5 is arguably the ultimate MF/HF command set,
yet it was arguably obsolete less than a year after introduction, replaced
where possible by the VHF-AM and later UHF-AM command sets that have
dominated since late WWII.  Sure there was a lot of HF command set use,
but it seems hard to justify that use from a performance standpoint.  But
when VHF networks and equipment were in short supply, one used what was
available even if there was better technology coming.

I know I also have an unpopular opinion about A.R.C.'s VHF technology.  I
know of no other way to characterize A.R.C. VHF developments except as an
almost complete and unproductive failure, especially when compared to the
output of Western Electric with the VHF AN/ARC-5 and AN/ARC-1, and Colonial
with the AN/ARC-3.  A.R.C.'s VHF products are very much in a blind alley,
and even their post-WWII VHF gear like the Type 12 was certainly second-string
or worse to what other manufacturers were producing.  (The RT-11A, part of the
A.R.C. Type 210 commercial VHF set, is a neat and no doubt very expensive set
from more than 15 years after WWII's end.)

There was little MF and no HF command set legacy in the post-WWII A.R.C.
designs, except for the oddball AN/ARC-39 and the AN/ARN-59.  There were only
the simplified R-10A BCB and R-11A beacon band receivers, and only R-13, -15,
and -19 modifications of the failed R-112 and R-113 VHF designs.

> The great HF Command Set of this time is unquestionably the ARC-2.

AFAIK, the AN/ARC-2 saw little real use as a command set.  In the aircraft using
it, every instance I've seen also used the AN/ARC-1 VHF command set, or the later
and similar AN/ARC-12 UHF command set, all replaced even later by the AN/ARC-27
UHF command set.  

I think it operated along side these VHF or UHF command sets as a sort of faux
HF liaison set, a role for which it was not suited if only by reason of its
low transmitter power.  But that's about the only reason it was on many
smaller post-WWII Navy and Coast Guard multi-engine aircraft with VHF or UHF 
command sets installed, such as the S2F-series carrier ASW aircraft.

There was also the innovative Bendix set that was about the same size as the
AN/ARC-2 which appeared two or three years earlier...the ten-channel crystal-
controlled 1942 Bendix RTA-1.  The USAAF adopted it unchanged as the AN/ARC-9
with a channel set of ten standard frequencies installed.  I suspect it
outperformed the AN/ARC-2, but it was much harder to put on a non-standard
frequency.

> Within their sphere, they were the "Apple" of their era.

That is likely an insult to A.R.C.  As one who has followed the business
policies of Apple since the Apple II in 1977, I have nothing but disgust
for Apple and the P.T. Barnum-hype associated with its founders and its
products.  If A.R.C. were like Apple, no other corporation, even in the
interest of national defense in time of emergency, would have been licensed
to produce any part of *anything* that A.R.C. claimed as intellectual property.
So forget about Stromberg-Carlson, Western Electric, Colonial, and others!
Forget about anything that could be serviced by anyone but A.R.C.!  Apple
is closed-market all the way.  Thank goodness than A.R.C. was not.

In spite of what I've written above, I admire the beauty and execution of
the engineering shown in the ultimate Type K, the AN/ARC-5.  It's undeniable,
and a real joy to see.  It hurts to see how hams thought they could improve
upon it.

I suppose if I were to identify an operational defect in the design of the
Type K sets, it would be the great difficulty of netting an easily upset
coffee-grinder receiver to the associated transmitter.  It can't be done
without external CFI equipment.  When the transmitter is keyed, the receiver
audio output is disconnected from the audio bus by relay, and the audio bus
is connected to the sidetone output of the modulator.  It would have been simple
to have a MONITOR/NORMAL switch such as was used in many liaison sets that would
drop out the sidtone relays and enable tuning a receiver to the output of the
transmitter during key-down.  That would have been especially valuable for the
ARA/ATA and SCR-274-N sets, for which there are pilot memoirs bemoaning the use
of coffee-grinder command sets, and praising channel-select VHF command sets.
The stabilized and locked-tuned MF/HF AN/ARC-5 receivers would have overcome
this netting problem somewhat.

> And lastly...  Because it's so much FUN :-).

It is amazing what clever people were able to accomplish with the early
technology that was available 75 years ago...with not a microprocessor
to be found for another 35 years!

Mike / KK5F