On reflection, building a jig to measure the crystal transmission as a function of frequency may be much easier than attempting to build an oscillator for an unknown crystal. However a suitable signal generator and detector are required. Once the crystal parameters are known its much easier to design a suitable oscillator circuit. Measuring the location of spurious resonances may also be useful.
Bruce On Saturday, 4 June 2016 9:52 PM, Bruce Griffiths <bruce.griffi...@xtra..co.nz> wrote: Some idea of the crystal equivalent circuit at the oscillation frequency would help considerably. Usually lower frequency crystals have a considerably higher series resistance than those operated at 1MHz or above. At frequencies below 100kHz or so a Meacham bridge using something likke a wideband FET opamp may be feasible. Bruce On Saturday, 4 June 2016 9:01 PM, Mike Cook <michael.c...@sfr.fr> wrote: Hi, I have a number of crystals either in glass, bakelite, ceramic or metal housings that I would like to get resonating . They are of three basic types. Square, or rectangular flat Round flat Bar square section Sizes range from 2-10cm or more in the longest face. Some have frequency markings. ranging from IKHz 5MHz. Others have none. Some are of Military origin, probably radios and as they have markings I can probably find a schematic from the radios to see how to proceed. There may be dedicated testers still around. I am not so interested in this bunch at the moment. Others have no known origin so I have no idea what oscillator circuits were used with them. In terms of vintage, I would guess pre 1940 to late 50s I have built a little Pierce circuit an tried a few. Some of the later 1-5MHz crystals will oscillate but there are a lot of parasitic signals as well as the supposed fundamental. I cannot make any of the low frequency / big crystals to react. So my question: If you had a crystal with unknown frequency and drive requirements that you wanted to investigate. How would you go about it? If I can get them going I will share the Adevs. I don’t have a spectrum analyser so I can’t do phase noise. Regards "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.