[time-nuts] notch filter for close in phase noise measurement

Richard (Rick) Karlquist richard at karlquist.com
Sun Oct 2 11:23:05 EDT 2016

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


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