[R-390] RE: New R390A owner with some questions.

[David Wise]

> From: W4QG [mailto:W4QG at CFL.RR.COM]
> 
> Radio works on all bands that I have tested so far
> except 1000kc to 2000kc. Seems stone dead on that

Welcome!  And enjoy your radios, they're joys, both
to work on and to use.

I agree with Walter that your prime suspect is the
RF tuned circuits.  There are separate sets for:
	0.5-1
	1-2
	2-4
	4-8
	8-16
	16-32

Contrariwise, most if not all of the crystals are
used on two or more bands each, so a bad crystal will
knock out several bands with no obvious numerical
relationship.

> Also, engaging the sharp position with the audio 
> response switch seems to kill the audio no matter
> what mode it is in.

"Sharp" = extremely sharp, as in "CW only".  It's only
a couple hundred Hertz wide.  Unless you're listening
to code, you'll never use it.
 
> I am in the process of downloading/printing the
> maintenance and operators manuals today. Any other
> documentation I should be thinking about acquiring?

If you're referring to TM11-856 or the other military
equivalents, they are interesting historical references,
but the one you really want is Al Tirevold's rework,
known as the "Y2KR2", available along with other
fascinating material at www.r-390a.net .  I particularly
recommend the "Final Engineering Report", which covers
the design choices that led to the R-390, and the "Cost
Reduction Report", a similar work for the R-390A.  But
then again, I'm a designer by trade, and this is my
favorite kind of technical reading.  My response above
about the sharp audio filter was gleaned from MIL-R-13947B,
the original product specification, available at the above site.

If you listen to AFRTS or other music on SSB, your VFO's
frequency stability is critical.  Unless embellished with
a time-delay relay to cut it out after power-on, an inrush
limiter may hurt this a bit, because as the first crystal
oscillator oven* cycles on and off, the mains voltage at the
power transformer bobs up and down several volts.  Not trying
to scare you off it, just letting you know.  It's what
started me on a solid-state ballast, which I'm sure this
group has heard far too much of :)

* This oven is enabled all the time, unlike the VFO and 2nd
oscillator ovens, which are controlled by a screwdriver-operated
switch on the rear panel.  Never turn them on, unless
you're in a tent in Antarctica.  It's hard on the VFO.
This too is mentioned in the above literature.

73,
Dave Wise (SWL in Portland OR)