Ian,
Does the LO frequency jump if you tap the crystal's can using a plastic
"rod" such as an alignment tool or pencil? If it does, and if all of the
soldered connections in the LO's circuit are sound, the jump and drift are
most likely caused by some "mechanical" fault within the crystal assembly
itself. The only cure in such cases is to replace the crystal.
73,
Geoff
LX2AO
On January 25, 2013 at 9:40 AM, Ian Greenshields wrote:
The LO on my XV432 transverter seems to be very unstable. I think it's
something more than just temperature drift as the frequency will sometimes
jump by several kHz. It's almost as if the crystal is hunting between
different modes of oscillation.
Prodding & wiggling the components in the LO circuit doesn't point to any
obvious poor connection, although the crystal itself is sensitive to being
touched, or heated by a finger. The LO alignment voltage at TP1 peaks at
about 3.3V.
I don't have the temperature oven for the crystal, although I think it's a
requirement. But I'm concerned about the frequency jumping and a frequency
drift of almost 10kHz which I would not expect even of a non-temperature
controlled crystal oscillator.
Any thoughts or pointers as to what could be wrong?
TIA, Ian G4FSU
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