[time-nuts] Are there SC-crystals out there in the wild that are not Overtone?

[Gerhard Hoffmann]

I had a Morion MV89A that would stop oscillating when Vtune was more 
than +600 mV.

So I cut it open to recover at least the crystal, for own experiments.

Pics are there:

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https://www.flickr.com/photos/137684711@N07/49585174873/in/album-72157662535945536/ 
    >

and then following the right arrow.


To get a first impression, I soldered the crystal to an SMA plug and put 
it on an

R&S ZVB-8 network analyzer and measured S11. I could see the 5 MHz resonance

as a 15 dB dip.  There was also a resonance at 5.45 and a smaller one 
another 90 KHz

higher. the +10% suggest that it is an SC cut.

But I could not see anything at 1 or 1.6666 MHz, so it should be a 
fundamental crystal?

Is that common?

I made most measurements at room temperature. I can turn the hot air solder

station down to 91°C which is not far away from the crystal's 87.7°C

inflection point, and I could see some variation on the 5.45 MHz 
resonance vs. temp.

I must build a fixture for the hot air because the sweep time at 1 Hz 
bandwidth

is close to eternal.


Is the un-harmonicity (???) between fundamental and overtones stronger 
with SC-cuts

than normal AT? I also could not see anything at 15 MHz. Next I'll make 
a board

for the PI fixture as described by Bernd Neubig in his crystal cookbook.


BTW I could see some more dips with >= 10 Hz resolution. I hope that 
does not mean

that the ZVB needs service.


cheers, Gerhard