[Boatanchors] Testing a crystal

[Gary Peterson]

This reminds me of something I read in Hints & Kinks in a 1930s QST.

The piece said that a crystal could be tested by placing its pins in series between a random length antenna and the antenna terminal of a receiver.  When the receiver is tuned to the resonant frequency of the crystal, there is an obvious change in the sound of the random noise coming out of the speaker.

I mentioned this to a friend at coffee one evening.  He was skeptical.  We went to his QTH and he brought out a box full of crystals and some clip leads.  By golly, it worked.  The noise sounds just like what happens when you kick in a crystal filter in the IF of a receiver.  This seems to be a stress-free method of measuring the approximate frequency of a crystal.  Obviously, its exact frequency will depend on circuit parameters.

Gary, K0CX  

“Note that the Q of the crystal is so high that you will not be able to
'land' exactly
on it unless you are using a digital signal generator (and you may have to
watch
the scope trace very closely to see the blip).
ian K3IMW”