I have made a shield out of Aluminum foil and 1/8" plywood.

Glue the foil to the plywood and mount it so any interferance, raido waves, do not have a line of sight
from the battery and the Rx.

Also 4.8 volts gives off less RF than 6.0 volts.

This has worked for me, but you will have to try it to see if it works for you.