Frequency modules can be changed by the end user because they are tuned to the specific frequency by the factory. It is also possible to have them changed to a different frequency by a service center. Retuning is less money than buying a new one.

Since these are older radios, my suggestion is to box them up and send them in for service. If you want them to be changed to channel 50 while they are there, the cost would be low. I sent two transmitters and a receiver to [link=http://www.radiosouthrc.com/]Radio South[/link] this winter to have them checked and retuned. The total, including return shipping, was a little over $60.

If the receivers are not new, I'd send them in too. In addition to checking, and adjusting, how well they are receiving, they can do a vibration test to insure they are ok.