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

[Bob kb8tq]

Hi

There certainly are fundamental SC’s out there. 

SC’s typically have motional resistances above 50 ohms. This usually makes transmission 
a better way to look for this or that resonance than impedance. 

Bob

> On Feb 25, 2020, at 7:42 PM, Gerhard Hoffmann via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> 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:
> 
> < 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
> 
> 
> 
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