In the July/August 2008 QEX magazine there is an article by VE5FP "Some Thoughts On Crystal Parameter Measurement" that may be of interest.
On Sat, Jun 4, 2016 at 11:01 PM, Bob Camp <kb...@n1k.org> wrote: > Hi > > There are two things you may be talking about: > > 1) The pressure springs on things like FT-243 holders, they are generic > springs. > > 2) The connection leads on plated blanks, they are indeed strange *and* > soldering to the blank is a big problem. > > I’m guessing you are in bucket number 2. > > Bob > > >> On Jun 4, 2016, at 1:41 PM, Mike Cook <michael.c...@sfr.fr> wrote: >> >> Thanks all for your advice, hints, tips and links. Lots to read , do and >> some hardware to check. I don’t have a frequency generator so I’ll have to >> go another route. >> >> Oh. One last Q. Has anyone tried repairing the « spring » wire electric >> connections on large quartz plates. In one large unit I have they had >> corroded and dropped the plate, luckily no damage. I have done one, but I >> have no Idea what the original wire composition was so have certainly >> induced some stray capacitance/resistance. It is possible that it was a >> filter rather than a frequency source as it was not in a vacuum. >> >> Have a good one. >> >>> Le 4 juin 2016 à 18:49, Bernd Neubig <bneu...@t-online.de> a écrit : >>> >>> >>> Tim Shoppa wrote: >>>> The Pierce logic-gate-biased-active oscillator is pretty reliable to start >>>> and will oscillate somewhere with most crystals from kHz to MHz. >>>> As you found out, it will often come up on one of many overtones. >>>> To reduce chance of coming at an overtone, a series resistor from logic >>>> gate output to the crystal is often enough. If not, a RC low-pass will cut >>>> down even further (although of course adding phase shift.) >>> >>> This is certainly the easiest and fastest way for a go/no-go test and to >>> find the approximate resonance frequency. >>> In the attached circuit diagram make CX1 and CX2 about 10 pF and RGK >>> several MegOhms. >>> The inverter gate should be preferably an unbuffered HCMOS or other fast >>> inverter. >>> For crystals in the MHz range you can replace RV by a short, for kHz >>> crystals make it a few kOhms. If testing small watch crystals @ 32768 kHz >>> or around, RV should be 100 kOhm at least. RV reduces the crystal drive >>> level (RF current) to an acceptable level to avoid overloading or even >>> damaging of the crystal. For low frequency crystals the RV-CX2 lowpass also >>> avoids start-up at the overtone. >>> It is recommended to add a second inverter gate at the output to isolate >>> your oscilloscope or counter input from the oscillator stage. Add some >330 >>> ohm in series to the output of the 2nd inverter, if you connect a coaxial >>> cable. Then terminate the coax at the oscilloscope or frequency counter end >>> with 50 Ohms, so the square wave form will be roughly maintained. >>> >>> In this circuit the crystal will not operate at its series resonance, but >>> at a load resonance with load capacitance of something between 8 pF and 10 >>> pF (depending on the inverter input and output capacitance plus the stray >>> capacitances of your test fixture). >>> If you want to operate the oscillator at a (low) overtone, such as 3rd (or >>> maybe 5th), you must add a series combination of 10 nF plus an inductor in >>> parallel to CX2. The 10 nF is to avoid DC short-circuiting of the output. >>> The inductor together with CX2 must have a resonance frequency mid between >>> fundamental mode and 3rd overtone (not at one of them). So the tuned >>> circuit acts like a capacitor at the 3rd OT and is inductive at fundamental >>> mode (thus the phase condition for oscillation is not fulfilled at the >>> fundamental mode) >>> Have fun >>> >>> Bernd >>> DK1AG >>> <Pierce_Logic_Gate.gif>_______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> "The power of accurate observation is commonly called cynicism by those who >> have not got it. » >> George Bernard Shaw >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
