Radio systems for sale
Most of the systems for sale do not have the channel number, and a lot of them come without crystals, I always assumed that you could change crystals in receivers as long as the new number was close to the original (low or high frequencies), but changing the crystal in the transmiter, crystals are not even listed for sale unless you use the same crystal for both transmiter and receiver.
If I were to buy a transmiter without crystal I would have to send it to the to the dealer to put the right crystal and perhaps tune it, I would not chance to use it on an airplane.
Perhaps I am being too careful, plase advise.