Magnus Magnus Danielson wrote: > Bruce Griffiths skrev: > >> Magnus >> >> For examples of the use of crystals in filters for cleaning up the >> output of a crystal oscillator look at the circuit schematics for some >> of the early crystal frequency standards. >> Crystal filters were used quite liberally in some of these to clean up >> the outputs. >> > > It's used in the step-up chain of the SR620 for instance. The SR620 has > a 10 MHz oscillator (TCXO or as in my case a Wenzel OCXO) which is > stepped up to 90 MHz using a fairly ordinary odd-order stepup and > filtering chain. The ECL logic counter frontend use this as coarse > counter frequency. The analog interpolators is a bit interesting in a > few peculiarities but nothing really exciting. > > Except if you believe that they actually use a Z5U capacitor (specified in the parts list) for the interpolator TDC ramp capacitor. If so, this would make for some interesting linearity and dielectric absorption compensation software.
> The crystal filters of that chain is setup in PI-filter style with the > crystals in serial mode. > > >> However it may be necessary to control the temperature of these crystals. >> > > Indeed. I wonder if he really needs that level of sine purity. An LC > tank should be sufficient to get started. > > The filter phase instability is reduced significantly if one uses LC filter traps tuned to the unwanted harmonics together with a low pass filter rather than using a high Q bandpass filter. > Cheers, > Magnus > > _______________________________________________ > 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. > > Bruce _______________________________________________ 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.