ORIGINAL: Redrum
If I have a Rx originally on ch 28 and want to switch it to a different channel can I just swap crystals or does the RX need to be re-tuned with the new one?
That depends upon the brand. If it is a Futaba, they are tuned HI and LO. If it is a Hitec it doesn't matter, all of their RXs are tuned to midlevel.
NOTE: IMHO, this fact alone makes it important to me to not to switch brands of Xtals between RXs.