Re: Crystals
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Chuck, I'm still looking for the HC-49S data that I have, but I did find some data from a batch of 8MHz HC-49U crystals that I have. I used the method outlined in Jim?K8IQY's excellent paper on crystal characterization. I built the impedance-reducing circuit to measure, and used an HP8640B as the signal source, Philips PM6665 counter and an HP400EL RMS voltmeter for measurements. I created a spreadsheet to do the math that followed Jim's procedure. The first 4 columns are measured, with the following 4 calculated. Out of curiosity, I added an entry for the crystal's frequency in the G3UUR oscillator test fixture (labeled Fosc). The last column is the difference between the resonant?frequency measured with the signal generator and the G3UUR oscillator. I expected to see a fairly?consistent difference between the two methods, but I did not. You can see that in the last number in the?spreadsheet. I think an advantage over the oscillator method is the crystal under test is only seeing very low power (-20dbm to -30dbm) which prevents heating. The crystal frequency in the G3UUR oscillator drifts quite a bit, although it does seem to stabilize over 5-10 minutes. I can't remember exactly, but I believe I waited the same amount of time with each crystal in that fixture before taking the reading. Maybe I have a problem with my G3UUR fixture? Hopefully this is readable. 73 Mike M.? KU4QO On Thu, Mar 13, 2025 at 1:03?PM chuck adams via <chuck.adams.phd=[email protected]> wrote: What is SSB?? :-) |