[time-nuts] Generation of very stable 10.001MHz for heterodyne freq measurement

John Ackermann N8UR jra at febo.com
Fri Jan 25 07:56:53 EST 2008

Anders Time said the following on 01/25/2008 07:23 AM:
> What is the best way to generate a very stable 10.001MHz(low E-13 or
> -110dBc/1Hz) to be to do high resolution heterodyne(Allan deviation)
> measurements?
> Using DDS?
> Using PTS 500 or 250 synth and divide? Using HP 8662A and divide?
> Some smart pll circuit by locking the 1000Hz to the reference in some way?
> Thanks
> Anders

Rick Karlquist has published a design for a very low noise synthesizer
designed for just this application.  Unfortunately, I don't have a link
to that handy, but it's on his website.

I just took a look at some measurements I did on a PTS-250-SX51 (special
version with low noise output to 25 MHz via an internal divider) and it
looks like it would barely meet your requirements -- around 2x10e-13 at
1 second, and about -115 dBc/Hz at 1 Hz offset:


However, that was at 10.000... MHz; the performance, particularly with
respect to spurs, changes as the decimal dividers kick in for more
complex frequencies.


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