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 <[email protected]>
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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