[Milsurplus] Crystal checker

[Hubert Miller]

>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 

Well, that's very interesting, Dave. I'm sure I have one of those things also but never thought of trying with another freq crystal. BTW, I was looking at some old I.C.C. literature on crystal testing circuits,
and in one particular LF tester, the only notable thing I could see different: the RF choke in the plate circuit was a lot larger !
-Hue Miller