I had a nasty problem once with the RFX. I unplugged every electronic device in the house, wireless access points, all computers, all cordless phones, plasmas even the refridgerators and dimming systems for the lighting. There was not change in the results. I swapped out the RFX and the Pronto twice with two different units, same problem. A radio buff advised me to take apart the RFX and compress the helical antenna so that the gap between the windings became narrower. I did this and the thing worked flawlessly. We still don't know what is causing the problem, but a tip fixed it.