Hi Guys,
I *used* to believe that the hermetically sealed HC-6 type of crystals were
impervious to aging & changing frequency over time---until I started to
seriously play around with the old Heathkit SB-line of receivers &
transmitters, that is! (THAT'S when I learned why the hairline cursor on the
analog dial read-out is adjustable on those rigs! Hi Hi).
Drake equipment from that same era is certainly not immune to the issue of
aging crystals. Proof of the pudding is when you "band jump", leaving the PTO
alone: amazing how much the cursor has to be re-set on some bands to still be
able to copy the 100-KHz crystal calibrator.
But that's little hardship, & both the Heath & Drake engineers took that into
account by way of incorporating these features.
What can REALLY be vexing, though, is when the crystal(s) used in
carrier-generating oscillator frequencies "migrate": I once had an SB-102
transceiver that sounded very tinny & nasal-sounding on LSB only---much to my
chagrin, THAT carrier generating crystal had shifted just enough so as to put a
goodly portion of my signal REMOVED from the passband of the IF filter!
No amount of dial tweaking / cursor re-adjustment would cure THAT condition!
: >)
~73~ de Eddy VE3CUI - VE3XZ
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