Hi You don’t necessarily need to convert to a 12.5 ohm system. A lot depends on just what your objectives are.
It a bit like needing a fancy Fluke Hart Chub thermometer if you are only after a couple of degree accuracy. The tools vary depending on the job. Bob > On Mar 1, 2021, at 3:23 PM, EB4APL <eb4...@gmail.com> wrote: > > My response got lost in the Internet, so I repeat the info. > > If you have access to a Network Analyzer, either Scalar or Vector, you can > measure the crystal parameters. You need a test fixture (it could be > homemade) to convert the 50 Ohm analyzer impedance to 12.5 Ohm and you very > slowly sweep the crystal to obtain its serial resonance (frequency and > attenuation) the and the -3dB points frequencies. From these measurements > there are simple formulas to obtain the motional resistance, inductance and > capacitance, and the crystal Q. > > Some professional Network Analyzers seems not to be very adequate to do this > because they cannot sweep slowly enough, but some low cost hobby type > analyzers have a mode for measuring crystals with these calculations > integrated. One example being the Poor Ham Scalar Network Analyzer which has > a function for specifically measuring crystals using a step rate of 1 Hz and > the nanoVNA, that can measure the resonance point and you do the > calculations. A program with the measurements and calculations integrated is > under development at this time. > > This an example of the PHSNA output: > > Crystal Id: 8 Mhz #3 > Peak Frec. (Hz): 7996356 > Bandwidth (Hz): 354,5 > Rs (Ohm): 24,3 > Lm (mH): 22,13353409 > Cm (pF): 0,01789803 > Q: 45763 > > Regards, > > Ignacio EB4APL > > > El 01/03/2021 a las 0:35, Dan Kemppainen escribió: >> Hi All, >> >> I've picked up a couple of old crystals. Mostly because they look neat. They >> are 1Mhz, in a glass tube. The quartz is ~25mm dia, at about 1 mm thick. Was >> able to get them to oscillate using a Colpitts circuit. They will oscillate >> at 2.851Mhz (probably some strange mode) if given the chance. >> >> I've been scouring my reference books here, and haven't had much luck >> finding any details on how one would even guess at the parameters of a >> quartz like this. >> >> There area few numbers on them, 33 stamped on the side, 1000 (KHz???) on the >> top, 87 on the top, and hand written 501 (probably a SN). Digging on line, >> I'd guess an AT cut based on thickness. I'm guessing the 33 is capacitance >> in pF. 87, might be year. >> >> If any of you have any suggestions on where to find information on how to >> get something like this to oscillate properly, guess at correct parameters, >> or even measure any of the parameters I would really appreciate it. >> >> I'm sure these are really nothing special, but it would be neat to give them >> a fighting chance to show what they can or can't do without breaking them! >> >> Thanks, >> Dan > > -- > El software de antivirus Avast ha analizado este correo electrónico en busca > de virus. > https://www.avast.com/antivirus > > > _______________________________________________ > 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.
