How would I tell the difference between the Futaba R127DF FM 72MHz Low and the Futaba R127DF FM 72MHz High.

I'm trying to rule this factor out on one of my planes I'm having radio interference on my Futaba R127DF FM 72MHz Low on channel 34. All my planes are on 34 and no other bird is having this problem. The reciever and crystal are both new and never been flown. I realize that does not rule out that there is a problem.

I wondered if there was a way to tell the difference between high or low?

Thanks, Ken