RE: Illegal radios?
That's right. Here in the U.S. our governmental department that regulates the airwaves has deemed it illegal to swap frequencies in the transmitter. We can swap them in the receivers. We share the same bandwith that other consumer devices are on as well as some commercial frequencies. The channels we use are seperated by 20khz, I believe, so there isn't much room for error. If someone swaps out a transmitter crystal and doesn't have the xmtr retuned, it could interfere with other transmitters at the field or some of the other nearby users of the same band.
Jesse