[Milsurplus] Prc-6 frequency stability

[Jay Coward]

In the movie "Mars Attacks", POTUS (Jack Nicholson) uses a PRC-6 while riding in a Jeep.
Jay



-----Original Message-----
From: Mike Morrow <kk5f at earthlink.net>
To: Robert Newberry <N1XBM at amsat.org>; milsurplus <milsurplus at mailman.qth.net>
Sent: Mon, Aug 6, 2012 10:01 am
Subject: Re: [Milsurplus] Prc-6 frequency stability



 I have a prc-6 that no matter how many times I bring it on freq it likes to
 drift. Today testing it I had it drift up to 51.16. Also it would drift
 down to 51.1. Also radio is rocked for 51.000.
Ho did you align it?  The ID-292*/PRC-6 is probably the quickest way, but
ll except the earliest manuals tell how to do it with a multimeter.
As John/K9WT said, there is almost *no* probability of the crystal being the
roblem.  The discriminator adjustment actually winds up setting the frequency
f the transmitter through the crystal-controlled receiver and transmitter AFC
ircuitry.  Any problems in that circuit may cause transmitter frequency control
roblems.  I recommend the 1955 Operator ( http://www.ebay.com/itm/350269043938 

nd Maintenance ( http://www.ebay.com/itm/350277705874 ) manuals if you don't
lready have them.  The ID-292*/PRC-6 alignment meter shows up on ebay fairly
requently, or might be available from someone on this list.  I'm sure you
now that the setting chart in the unit is worthless, and is meant only as
tarting points for the alignment using the ID-292.
That said, I've played around with several AN/PRC-6 units since I got my first
ne in 1969 from Navy MARS.  I've never had any problems that were not the 
esult
f mis-alignment.  My current favorite is an RT-196A/PRC-6 that was re-labeled
n Hebrew by the Israelis.  It has a few replacement non-US parts.  I use a
mall DC-DC supply module purchased from Italy, fed by a 6.3 vdc SLA battery
 http://www.ebay.com/itm/160856820093 ).
I last aligned it about three years ago using an ID-292A/PRC-6, plus a frequency
ounter to fine set the frequency.  I tested it last night, and it was still
1.000 MHz at start of transmission.  It then very slowly varied +2.5/-0 kHz
fter transmitting for more than a minute continuously.  That's pretty good
tability both in frequency and in long-term retention of alignment, at least
or a 60-year-old 13-tube battery-powered set that was a real wonder of
iniaturization in 1951.
I have tested it over a half-mile distance with a 1978 RT-1113/PRC-68.  (The
T-1113 squelch does not require 150-Hz tone.  There was good-sounding AF at
oth ends, except for a little whine from the modern DC-DC power module that
as heard at the AN/PRC-68.
I last saw the AN/PRC-6 in limited use by the USMC at Little Creek, VA, in 1972.
 remember thinking at the time what obsolete gear the USMC retained in their
nventory.
Mike / KK5F


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