[R-390] Very rare R-390x spy accessory

[Terry O'Laughlin]

There was a spectrum display designed expressly for the R-390 series of 
radios, The Communications Electronics Inc. SM-8512.  I have added 
information on it to my website.
http://watkins-johnson.terryo.org/SDUs/SM-8512-6.htm

The SM-8512 is very rare, as R-390 accessories go.  It is a 455 kHz 
spectrum display unit in a 2 rack unit high package.  It uses a 3XP1 tube 
and is an all nuvistor design.  I have included photos of the unit, the 
original catalog sheet and pages from the manual describing how to add a 
wideband (30 kHz) pre-filter IF output to the R-390 for use with a spectrum 
display unit.

There was also an SM-8513 designed for simultaneous display from two R-390x 
receivers, but I have never seen one in 25 years of following the CEI and 
WJ equipment lines.

In addition to domestic sales, three version of the SM-8512 were sold to 
the government:

IP-861/URR    NSN 5820-00-105-3064   a plain SM-8512
    contract  F41621-73-C-0075   Feb 1973  (Air Force)

IP-866/URR    NSN 5820-00-933-7909   an SM-8512-4
    contract  NOM73611           July 1966  (Navy)

no designation or NSN   an SM-8512-5
    contract  DA18-119-MAC-03432(X)  (NSA)

Happy hunting,
Terry O'
http://watkins-johnson.terryo.org/