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

[Magnus Danielson]

Hi,

I agree in general. However, I do see that other work to get good 
resulst have been done when SC-cut is considered, so rather than SC-cut 
as a cut is better, it becomes somewhat of a tell-tale of that other 
work being done properly. I.e. it is meaningless to take the step to 
SC-cut when other defects dominate so the SC-cut properties only makes 
things more expensive than the AT-cut.

As far as I remember and know, you can achieve about the same 
phase-noise properties as you hit about the same bandwidth from the Q, 
and noise contribution is about the same. So, it boils down to do the 
supporting amplifier well.

Cheers,
Magnus

On 2022-06-08 06:27, Bob kb8tq via time-nuts wrote:
> 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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