>I would make a small LC tank centered at 12Mhz across a scope input with an
>arial close to the xtal and use a scope output into a frequency meter
>although a good scope would measure the freq as well.

I would doubt the ability to read to 1Hz in 12MHz on a scope, unless it has
a really good digital readout, but the accuracy of the crystal in the scope
timebase is probably about the same as you are trying to measure.

A good frequency counter will probably trigger from a pickup coil such as
mentioned, but then it will need a proper ovened timebase which is regularly
referenced to a standard to get anything meaningful of the accuracy you are
looking for. Remember that you will really need a standard good for 0.1Hz in
12MHz to make your efforts worth while.

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