The motional inductance (Lm) and motional capacitance (Cm) of radio frequency crystals are of importance when designing crystal filters for narrowing bandwidth of a device (usually a radio).
I soldered a circuit together and used a test setup invented by a HAM (Hobby Amateur Radio) guy. The math looked scary but you just plunk in your numbers.
You test 50 or so crystals and then group the 10 most similar ones and use them.
Cs = size of the capacitor in the circuit.
Co = measure the capacitance of the crystal with a meter.
^f = the delta (change) between measuring the crystal with and without the capacitor switched on in the circuit. Subtract one frequency from the other.
F = the first capacitor off in the circuit measurement.
