I don't know for sure but I believe that flying in an area with RF interference reduces distance more than you would think. Everything stock, flying at 390', I have gone to 4200', 4400' and 4800'. With the booster, out to >7400' (although that was at 550'). This is with low humidity and little or no interference. I am careful about how I aim the antennas of course, and always start with the repeater fully charged. On the 7400' flight I was powering the repeater from a usb power pack. I haven't worried about the TX batteries much. Using eneloops and I charge them every 20 or 30 flights.