As to "oscillation": most older octal style crystal ovens have no proportional control at all, they are simply a bimetallic click-on-click-off thermostatic switch that is on or off, and after initial warmup they cycle up and down every few minutes.
A tiny fraction of the better octal crystal ovens have some proportional heater control. Tim N3QE On Thu, Oct 2, 2014 at 2:10 AM, Magnus Danielson <mag...@rubidium.dyndns.org > wrote: > David, > > The character of starting high/low and then stabilize some 5-30 min later > is typical of oven oscillators. Underdamped ovens have been seen before, I > have even seen one on the brink of oscillation. > > TCXO will not have the same wide range, as it compensate for the > temperature. > > Cheers, > Magnus > > > On 10/01/2014 10:11 PM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote: > >> Further to my question the other day about what type of oscillator was >> used in the HP 8720D VNA, fitted with the high stability oscillator >> option (1D5), here is the frequency as the instrument is switched on, >> after being powered off for 2-3 hours. >> >> The oscillator appears to start too high in frequency, overshoots >> downwards, then settles down. It would be a somewhat useless exercise >> collecting data for much loonger and looking at in detail, since I >> don't know the accuracy of the HP spectrum analyzer. But that had been >> on for at least 24 hours. >> >> The measurement system was an HP 70000 system spectrum analyzer, >> fitted with the 70310A precision frequency reference. This has not >> been calibrated in years. >> >> I will get one of those Jackson labs GPS frequency references, then I >> will know what the frequency is!! >> >> Assuming the crystal frequency is only a function of temperature, (and >> I know that not to be the case), it looks as if the oven is under >> damped to me. >> >> Is this behavior typical of a TCXO, OCXO or whatever ?? >> >> Any comments??? >> >> Dave >> >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/ >> mailman/listinfo/time-nuts >> and follow the instructions there. >> >> _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.