On 2/27/20 10:45, Richard (Rick) Karlquist wrote: > OTOH, you could build a simple Colpitts > oscillator and see where it oscillates. > That's what they did back in the dark > ages. > > Any time nut should be up for that. I was going to suggest pumping it with white noise and then doing a long FFT to see which bin has any energy in it to get into the ballpark but building an oscillator seems to be far and away the simplest solution. > > Rick N6RK > > On 2/27/2020 5:35 AM, Bob kb8tq wrote: >> Hi >> >> Ok, so just to run the math: >> >> 5 MHz / 2.9 = 1.724 MHz >> >> If the Q at the fundamental is 500K (a wild guess) then 1.724 MHz / >> 500,000 = 3.4 Hz >> >> In a world where a synthesized sweeper *might* be stepping in 10Hz >> steps, that’s an >> easy one to miss. >> >> Bob >> >> >>> On Feb 26, 2020, at 11:40 PM, Bernd Neubig <[email protected]> wrote: >>> >>> Hi Gerhard, >>> I am rather sure that it is a 5 MHz 3rd overtone crystal. >>> the resistance should be in the 80 to 110 Ohm range and Q about 1.5 >>> million. You can see the resonance without ringing in a span of 100 >>> Hz or smaller with a sweep time of 10 sec minimum. >>> See attached the response of a 5 MHz SC3 crystal in HC-40/U package. >>> Indeed the 5.45 MHz is the B-mode which has a temperature >>> coefficient of -30 ppm/K >>> Because the crystal blank has a plano-convex shape. The overtones >>> are quite far away from 3 times or 5 times the fundamental mode. 3rd >>> overtone is about (rough guess) 2.9 time of fundamental mode. >>> To find them you must really carefully sweep around a few 10 to 100 >>> kHz span with slow sweep time a narrow bandwidth >>> >>> Regards >>> Bernd >>> DK1AG >>> >>> -----Ursprüngliche Nachricht----- >>> Von: time-nuts [mailto:[email protected]] Im Auftrag >>> von Gerhard Hoffmann via time-nuts >>> Gesendet: Mittwoch, 26. Februar 2020 01:42 >>> >>> 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. >>> >>> >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] To unsubscribe, >>> go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >>> <5MC5735H.jpg>_______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there.
--  <https://www.lloyd.aero> Brian Lloyd 706 Flightline Spring Branch, TX 78070 [email protected] <mailto://[email protected]> +1.210.802.8359 _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
