I am using a fury board with on off board oscillator. So a thermistor is representing ocxo current. Right now without tempco I have 1.7 ns sd in ti. If I can eliminate "bumps" when the temperature changes slightly I can back the efc gain down below my current setpoint of 0.5. Right now if I go any lower on efc gain the thermal changes perturb the system a bit too much. When the temp is constant I can bring the efc gain way down...and therefore the sd to close to 1 ns. What I am trying to achieve is a much more stable and narrow time interval. Current performance is pretty close to as good as it gets for a gpsdo but I think I can do a little better.
Sent from my iPad On Oct 17, 2012, at 5:55 PM, Azelio Boriani <[email protected]> wrote: > Yes, usually increasing temperature increases frequency, so if you see an > oven current increase then slightly take down the EFC (and the other way > around if the current decreases). > > On Thu, Oct 18, 2012 at 12:47 AM, Rick Karlquist <[email protected]>wrote: > >> Bill Dailey wrote: >>> If I wanted to try to compensate for temperature variation of my OCXO... >>> where would I attach a thermistor? What would be a good method of >>> attachment to best respresent the OCXO temp without opening the OCXO and >>> without an undue influence of ambient temperature? The OCXO in question >>> is >>> Datum 1111C... was thinking of using thermal epoxy to hold it down and >>> then >>> putting some insulating material (suggestions) on top of it. >>> >>> >>> >>> -- >>> Doc >>> >>> Bill Dailey >>> KXØO >> >> Probably easier to monitor oven current and use it to tweak the >> set point of the oven or tweak the EFC line of the oscillator. >> As I explained in my 1997 FCS paper on zero gradient ovens, >> the gradient is the main thing limiting thermal gain. If you >> have a serious gradient problem, then locating the thermistor >> far away from the crystal (probably much farther away than the >> internal one) isn't likely to be productive. >> >> The other issue to be aware of is that at some point, the >> tempco of the electronics comes in play, as explained in my >> 1997 FCS paper on bridge stabilized oscillators. Increasing >> the thermal gain of the 10811 beyond 1,000 doesn't improve >> the tempco because of oscillator circuit pulling. You could >> possibly improve the tempco by using oven current to tweak >> the set point. This might cancel out circuit pulling drift, >> regardless of what was going on with the crystal. I've never >> actually tried this, but it would be good research project >> well within the ability of any time nut. >> >> Rick Karlquist N6RK >> >> >> _______________________________________________ >> 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. > _______________________________________________ > 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. _______________________________________________ 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.
