If you start off viewing the crystal in series (S21) I believe that you'll be able to see some response far enough away from the resonance to make it easier to find.
Dana On Thu, Feb 27, 2020 at 9:39 AM Magnus Danielson <mag...@rubidium.se> wrote: > Hi, > > Even if my VNA steps in 1 Hz if I ask it kindly, it can be a bit > teadious work to find it. > > Cheers, > Magnus > > On 2020-02-27 14:35, 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 <bneu...@t-online.de> 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:time-nuts-boun...@lists.febo.com] 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 -- time-nuts@lists.febo.com 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 -- time-nuts@lists.febo.com > >> To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > >> and follow the instructions there. > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
