[time-nuts] Re: Is SC the most stable cut for lowest phase noise?

[hans-georg at lehnard.de]

Hi, 

read this paper from Connor-Winfield about differences AT/SC cuts. 

http://www.conwin.com/pdfs/at_or_sc_for_ocxo.pdf  

Am 2022-06-08 04:04, schrieb Ross P via time-nuts:

> Hello,My first post.I have created a 64-bit frequency counter, 15.9 digits after converting to floating point. 
> Oscillator random walk is +- 0.01 ppm with an SC cut crystal at 10 Hz filtered, and 0.1 ppm with at cut.Is it the crystal or the oscillator electronics (inside a can) that determines the noise?The oscillators I am using are 1 double oven SC 10 MHz vs 1 single oven AT cut 10 MHz in one test,and 2 generic crystal oscillators (on a Terasic DE1 cyclone II FPGA board) for the other test.I assume the single oven oscillator will have better stability than commodity oscillators.I am able to chart random walk at up to a few thousand samples per second at full double precisionresolution, and FFT shows some alien tones in the walk pattern that come and go suddenly, I thinkdue to oscillating mode changes in the oscillator itself, mostly show in the commodity crystals.My question is: is the SC quartz the most stable for random walk.I would like to know if such a frequency counter / alien to detector is useful enough to be producedfor sale? It would require at least 3 separate frequencies of
refer
> ence time standards and > 50Klogic elements in the FPGA for 3 cross coupled monitors to cover a range of 0 to 50 MHz. 
> Quite a risk if no one needs it. 3 separate high stability reference oscillators are expensive.rp
> 
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