Yes... if the C217 trimmer was not already at the very minimum setting! I was thinking of possibly removing it altogether, maybe adding back a smaller fixed C. All three of my units are pretty low in VCXO center frequency, and in fact I wonder if that's the reason they were on the surplus market in the first place.
> -------Original Message------- > From: Bob Camp <[email protected]> > Based on the frequency plot of your unit, it swings about 35 Hz high and > about 170 Hz low as it sweeps. You could bump the trimmer on the VCXO and > move it up by about 70 Hz or so to keep it from running out of range. Since > the VCXO is trending down in frequency as it warms up, this may be needed > sooner rather than later ... > > -----Original Message----- > Great detective work Scott! I'll bet Channel 4 is voltage to the VCXO. It > is driven up and down at startup searching for the lock, then it settles > down, but the oscillator components are also affected by temperature so the > VCO voltage would logically track the temperature too. At least it seems a > reasonable theory. > > For example, look at this plot of the 10 MHz output frequency after > powerup. It has a similar look to your Channel 4, except for the post-lock > drift. > https://plus.google.com/photos/109928236040342205185/albums/5680473650837554 > 113/5681715799377076466?banner=pwa > > -John Beale _______________________________________________ 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.
