[Milsurplus] receivers

[aGEnuine Ham]

Group:

The discussion about the genesis of the R-390 series receivers arises
regularly, and various reasons are proffered for the rationale of its
appearance.  Let me offer the following:  Most receivers designed for
military use are relatively insensitive, broad band IF (i. e., easy to
tune), and field repairable, by design.  The 390 hardly fits.  A current
example of military receiver sensitivity popped up in some shipboard work
I was recently involved in, and I took a close look at the SPAWAR
sensitivity specifications on current procurements of shipboard DF.  Not
very sensitive.  Accurate bearings, but doesn't respond to weak signals.*
 

So where is this diatribe leading?  The reason the R-390 is so desirable
for ham and similar use is that it is unusually sensitive while
exhibiting good rejection of unwanted signals (high dynamic range, unlike
most present production equipment), the frequency calibration is
excellent for the era, it has lots of flexibility in IF bandwidth, and so
on.  So who would be the target market for this design in 1950?  There is
only one answer, and it is not tactical or even strategic military
communications.  It is spelled SIGINT.  And, back when those designs were
initiated, no one could even whisper NSA in public.  So, the genesis of
these boxes remains shrouded in the tight Cold War secrecy of the time,
and it is difficult to refute most of the wild stories which arise in the
vacuum of this lack of factual information.  But, that venue had the
quantity of funds necessary to initiate an expensive design like the 390,
while the rest of the military suffered along with tactical equipment of
much lesser performance which was typical of the time.  I had a friend
who repaired BC-610s at night in the stream beds in Korea in this time
frame, the SCR-x99 series being still a mainstream radio system.  There
are several other products which were funded in the same time frame, some
of which remain classified, and others which are no longer held close,
but have all been destroyed and the hardware has never been seen by the
public, except perhaps in the NSA museum.  I'm still looking for a meter
from an FLR-13 (WARS), for example.  Finally, the way the security
process works, most if not all of the people who actually worked on those
products in the early days signed lifetime nondisclosure agreements, and
it is likely that they have never been officially notified that the
information has been declassified, so they *could* still be prosecuted
for violation of the secrecy laws if they chose to go public with their
knowledge.  And, these days, with the prevailing Federal attitude about
such, I for one, would not take the chance.

Hammarlund independently continued their successful Super-Pro line with
the various versions of the SP-600, and that design was preferred by some
operators based on easier band changing, and more familiar tuning
characteristics.  But, the dial calibration was not as accurate, and the
390A, with the mechanical filter(s) also gained a notch on the
selectivity battle.  Hallicrafters built their version of the R-274 and
called it a SX-73, but it suffered some of the same shortcomings of the
SP-600, particularly dial accuracy.  TMC popped up with their HF line
about this same time, and other short lived HF radio designs also
appeared.  Has anyone ever wondered where the market was for all these
high performance HF radios?  Hams? Point to point? Maritime? I submit
that the actual market was invisible to most people, except for the few
in certain carefully chosen locations.


*  There is actually good justification for this (according to SPAWAR). 
The fog of war at sea produces a plethora of signals, and DFing on
intermod products of friendly transmitters and the like is distracting
and undesirable.  Also, the signals of interest are 'usually' submarines
within torpedo range.  So, relatively strong ground wave (sea wave?)
signals provide the targets for shipboard DF, and higher sensitivity than
required to accomplish this mission is undesirable.

73,
George
W5VPQ

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