I just finished my matching of qty 100 4.9152 MHz CTS crystals purchased from Mouser. I measured the entire set compared to a 48 hour warmed 5328A counter timebase (1 Hz resolution on the digits) and pulled sets for all 6 crystals for the Norcal 40A, making sure I optimized the selection so that the 4 filter crystals were as close as possible. I had a final 16 sets of crystals where the filter crystals were all well within the desired 10Hz spread.
Keeping in mind that the timebase drifts over time, I matched the crystals once, then sorted them all in frequency order. I then rematched them the next day - The goal was to measure crystals closer in frequency in a shorter period of time to minimize effects on drift. The resorted list did not vary much from the original day.
I ended up with the four crystals for the filter as follows:
2 sets - within 3 Hz
6 sets - within 2 Hz
2 sets - within 1 Hz
6 sets - with same value, i.e., 0 Hz difference
I know there are more variables that impact accuracy, but I suspect I got all these sets within 10Hz.
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72 - John - N0HJ
