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

[Bob kb8tq]

Hi

Simple answer is: no.

More complete answer is: no

There is a lot more to stability than just the crystal cut. Having this or that cut is 
in no way a guarantee that the result is “better” than some other cut. Indeed there
are more exotic cuts than the SC that improve on this or that. There are also mounting
/ fabrication techniques that improve on this or that, regardless of cut. 

All that said, the “typical” SC cut based OCXO is likely newer than an AT or BT cut
alternative. Various improvements here or there are likely to make it a bit better than
the other examples …. ( but not always )

Bob

> On Jun 7, 2022, at 6:04 PM, Ross P via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> 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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