How do the piezoelectric crystals work with copper antennas in CB radios?
In: Physics
Piezoelectric crystals work two ways. You can apply mechanical stress, and they will create a voltage. Or you can apply a voltage, and they will mechanically deform.
A crystal in an oscillator circuit uses the latter of these. If you carefully make the crystal, it will have a frequency that it “wants” to resonate at. So if you have a 15.315 MHz crystal, for example, you put it in an unstable circuit. It will quickly (if the circuit is designed right) make the whole circuit oscillate at the crystal’s natural frequency of 15.315 MHz.
This doesn’t really have much to directly do with the antenna in a radio. The crystal provides a fairly stable reference frequency that the radio circuits can then use for tuning.
IIRC, some old-fashioned CB radios will use multiple crystals to tune in specific frequencies more directly, but that would be an unusual thing to do these days.
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