I've stayed out of this thread because I post too much.
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Anyway I tried several of these modules and found them to be useless for any thing resembling precision.
I had 3, one in each color, and all drifted...drifted really bad. I tried a insulated case with a clear lexan window, tightly regulated power supply.
Before spending too much effort, get a known frequency reference, 100MHz is gooed, connect it and monitor the displayed frequency for an hour or so.
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I used a local FM station on 98.1 MHz as my reference.
I used a dipole, a narrow pass RF filter, two ganged FM boosters, with another narrow pass filter between them and a home made high gain amp, with another narrow pass RF filter between the output of the last booster and final amp. I had ~1 V 98.1 MHz signal, a spectrum analyzer showed the FM stations nearby in frequency were way down.
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Another option might be a 10 MHz disciplined oscillator, extract the 10th harmonic with a filter and amp.
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I ended up going with a Jackson Harbor pre-scaler kit
And a Tektronix CF250 100 MHz frequency counter a friend gave me.
My combo counts to 1500 MHz with the expected last digit bobble.
It is a lot larger but extremely accurate after replacing the 3.58MHz reference with a reference derived from a GPS disciplined oscillator.
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I ended up junking all three counters and only saved the brass hardware. An expensive lesson.
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Another poster suggested replacing the stock oscillator on the frequency counter module with a precision unit. That would probably work.
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