I recently sent an email directly to Futaba with that exact question. Their response was that their receivers are "center" tuned. Which means that when you buy a low band receiver, it's tuned in the "center" of the available channels. So the best channel on the low side is either 22 or 23 and the high side would be 47 or 48. The further away from these you get, the more it affects range. Although for our purposes this is negligible.