Hi Well, if you ever get back into it:
You play games with varicap diodes to straighten out the curve. You may bias them, you might put them in parallel, you might put a coil or a cap across them. You can get the curve plenty flat enough for a control loop. Hopping / discrete steps generally means you have to much drive on the crystal or some other circuit gotcha. The crystal its self and the tuning diode have no steps in them. They just aren’t complex enough devices to get into stepwise behavior. Drive power on an OCXO will pretty much always be below a milli-watt. A typical design will be in the range of 1/10 to 1/100 of that power level. Bob > On Jul 9, 2019, at 5:36 PM, Glen English VK1XX <[email protected]> > wrote: > > and non monitonicity in the device is the death of a control loops. > > My attempts at building good OCXOs using cheap AT crystals in the 90s was > thwarted by.... non monotonic bending crystals ! > > And everytime they would wake up, the monitonicity would be in a different > part of the control curve.... > > and they exhibited hysteresis, like defined steps , this seems to be the case > with most crystals, the harder you looked, the more undesirable imperfections > you found... > > > > On 10/07/2019 5:57 AM, David G. McGaw wrote: >> Leo - >> >> I do believe you mean non-monotonic, rather than non-monotonous. Not >> being monotonous is a good thing. :-) >> >> David N1HAC >> >> On 7/9/19 1:20 PM, Leo Bodnar wrote: >>> It's not very good, it is highly non-linear and even wor > > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
