bhanley

Albert S - using different manufacturers crystals is a minor part of the issue. The main point is that to be legal you have to send the transmitter back to the manufacturer to be retuned each time you change. Also, it turns out that there are a variety of reasons why you might want to freely (and often) change crystals, eg, have different planes on different freq, or use it as a way to handle crowding on a particular freq at your field, etc, etc... Note that as indicated above you can legally swap complete RF modules such as are used on the higher end JR radios. These are, of course, much more expensive than a simple set of crystals.
Bruce