LP posted:

"Reading this just makes me feel old cause I remember when the R-390A
was the Navy's premier state-of-the-art SSB receiver, and that was in
the SIXTIES!!!"

If being an R-390A user makes you feel old, having been a member of
design team of the T-368 transmitter that accompanied the R-390A in the
Army's GRC TTY communications vans, then I must be ANCIENT! ! ! ! !

Actually, the R-390A is still a very competitive receiver commanding
very high prices on eBay, perhaps second only to the Collins 75A4
(whose design is heavy based on certain sections of the R-390A). At the
time (circa 1960) many firms tried to duplicate the R-390A's variable
frequency local oscillator but failed because no one could figure out a
production alignment methodology that would produce the same frequency
linearity as did the Collins produced LO unit. (At least at B&W we
couldn't.) This involved the precise bending of a capacitive loading
finger strip that paralleled a rotating, variable inductance coil and
compensated for a small amount of tracking error in the coil's
windings.

The old 'boat anchor' receivers still hold an advantage over most of
the current generation of solid state units -- That is, when they break
you can fix them yourself! :-)

IIRC, two versions of the R-390A were produced, one with a conventional
tuning dial and the other with a geneva mechanism type counter showing
the tuning setting but not the frequency. The receivers were produced
by a number of firms, but so far as I know all of the LOs in them were
manufactured by Collins Radio.

Ah, memories....

Harry C.