ORIGINAL: wings

Ok, that kind of makes sense, except for the rx being tuned with a !QUOT!perfect!QUOT! crystal. As you said, everything has a tolerance, nothing is perfect.

I kind of understand what you saying, but I am still unclear about the !QUOT!tuning!QUOT!. And I am unclear about how changing a crystal can cause such a problem. Do you actually harm the crystal when changing it,

NO

or is it a calibration thing?

YES

Is tuning actually tweaking the tx with the crystal to get the correct frequency?

YES

If this is the case, how is it !QUOT!tuned!QUOT!? Do they adjust a potentiometer or something?

Usually a small variable capacitor in the oscillator circuit fine-tunes the oscillator to frequency

Wings