Following the good advice I received about increasing the value of the trimmer capacitor, I replaced the trimmer which was originally 3-12pF, with another one which was 2-22pF.
This has given the additional adjustment range to allow me to pull the crystal to meet the specification. It's not mega-stable, varying between 9.9999619 MHz to 10.0000232 MHz over the course of a minute or so as the thermostat cycles, but certainly within the 10ppm specification and varying up and down by about 6-7ppm. This is before the full 2 hour warm up period is complete, but I don't things will change much over the next 45 minutes or so. The stability seems to be improving as the warm up continues which is good. I may be able to tweak it so the variation is more evenly balanced around 10.0000000 MHz, but the trimmer adjustment is pretty sensitive. Still don't understand why probing with a 10Meg, 1pF load kills the oscillation stone dead until the next power cycle. Thanks to all Cheers Dave _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
