I don't know if there is such a thing or not, however, I do remember reading something (here) a few months back, that someone thought the UHF PRO remotes had 2 channels - A & B, and one of them was weaker than the other.
On the 6.3, you change from A to B from inside the battery compartment.
Otherwise... You can relocate your UHF antenna from the back of the receiver, to elsewhere, using a coaxal cable. Even to another room.