"N_Cook" wrote in -
september.org:

Michael wrote in message
...

Hi,
I regularly repair and restore vintage CB and ham radios. Older CB
radios often have had their crystals drift off frequency usually to a
lower frequency. When I use my frequency counter to align the crystal
back to it's intended frequency via a trimmer capacitor the frequency
changes as soon as I connect the counter. In other words what good
does it do to adjust the PLL reference oscillator to 10.240 MHz if the
frequency changes slightly when I disconnect the frequency counter?

pick off the signal with a scope(10Meg input Z) and feed CH1 out to the
counter.or you could trigger the scope on an ext.reference signal like WWV
and adjust the scope display for lowest drift.

Is there a way to minimize or eliminate the oscillator frequency
change when the counter is connected? My frequency counter is a Protek
B-818.




You should be monitoring a PLL o/p and inferring the Xtal f


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/






--
Jim Yanik
jyanik
at
kua.net