ORIGINAL: mike.p
let me ask a dumb question. the crystals frequency are catorgized by channels ? if so why not just go by the frequency.
Many years ago "Someone" decided that 'Channel 11' is easier to deal with than '72.010' but I do not know why.
As already written, you are not supposed to change transmitter crystals in the US. It costs $20 to $40 to get it done at a service center which is probably not cost effective for either of the units you have.
Receiver crystals can be changed by the end user. The Hobbico and Hitec receivers I linked yesterday can have any crystal (72.010 through 72.990) (channel 11-60) installed with no tuning issues. The Hobbico receiver uses Futaba crystals, which cost twice as much as Hitec crystals.