I have a Bud Radio FCC 90 Crystal Calibrator that came to me with a 200 KHz FT-241 crystal. I loosely coupled it to a counter and it registered 199.9 KHz.

This got me thinking a bit so I brought out a handful of FT-241 BC-604 crystals and found they all oscillated at their calculated frequencies, even at ~500 KHz. No joy with an 80 meter FT-243 however.

So beyond it's designed use as a 100KHz calibrator, the FCC 90 does the job as a LF crystal checker.

Dave N9ZC

On Sat, Jul 30, 2022, 8:44 AM CL in NC via Milsurplus <milsurplus@mailman.qth.net> wrote:

I must have missed the question about the crystal checker. I bought the X-Checker a couple years ago, and it seems to have disappeared from sale now. It works quite well and not expensive. But, when I went looking for it to send the link, it is longer there, it did bring up a lot of crystal checker circuits for home brewing, simple to complex. I have 3 of those metal crystal storage boxes that plugged into the FM tank radio, forgot the nomenclature, and out of all those crystals, only a few worked. The early FT241's were exceptionally fragile. Anybody need those boxes full of dead rocks to fill a hole in their transmitter?

Charlie, W4MEC in NC
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