> Maybe I'm missing the decimal point. What's the bandwidth of a crystal > filter relative to the spectrum out of the same crystal used as an osc? >
The oscillator's noise floor itself is superb, near -180 dBc/Hz beyond 1 kHz. That is only true until you do something with it. The idea behind the crystal filters is to get rid of the broadband noise introduced by the buffers and multipliers. You don't put the crystal directly in series with the oscillator, but rather after various multiplier stages. See the HP note "Generation of low phase noise microwave signals" at http://www.ke5fx.com/Scherer_Low_PN_Signal_Generation.pdf , especially page 23. The additional filtering won't necessarily solve Brian's problem of minimizing phase noise at circa 1 KHz from a 630 GHz carrier, though. That is beyond anything I have tinkered with. -- john, KE5FX _______________________________________________ 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.