Rick, Why hunt goose with the cannon? The post is about a simple(r) crystal notch filter, nothing more and nothing less. It is not about notch filters (in general) against quadrature method, nor about number of RF components or about their noise floor limitation. It is about this notch filter against other notch filters. As per simplicity, to mix 2 oscillators in quadrature one need the second oscillator, the high level mixer, the PLL and the baseband (FFT) analyzer. Best, Adrian
Sent from my BlackBerry 10 smartphone on the Orange network. Original Message From: Richard (Rick) Karlquist Sent: Sunday, October 2, 2016 18:35 To: Discussion of precise time and frequency measurement Reply To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] notch filter for close in phase noise measurement On 10/2/2016 12:56 AM, Adrian Rus wrote: > Hello list, > For those of you interested in phase noise measurement without using > fancy/dedicated gear, There is no free lunch here. The crystal has its own intrinsic flicker of frequency noise. You cannot measure below this noise floor. The technique you are talking about could be useful in particular applications, but is not a general replacement for "dedicated gear". I don't even see where this is simpler than mixing two oscillators in quadrature. In that case, the only RF component is a mixer and everything else is audio. Also, when using a crystal filter, you have to be careful not to overdrive the crystal. Rick _______________________________________________ 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.