Take your plane and set it on the ground and back away until gets too small to be able to fly. Then measure the distance. I'll be it is a lot close than you think. Range isn't a problem with today's transmitters. However, some receivers don't have the gain to be able to receive the signal. Mostly the park flier variety. Be careful trying to use them for glow flying. We had a couple of planes crash because the pilot was using park flier receivers. I crashed one of his planes when he asked me to trim it for him. He didn't say what was in it. I flew it to the end of our property approx. 400ft and it dove into the ground. He looked at me, and said " Last week my trainer did the same thing at the other end of the field!!" That is when he told he was using park flier receivers in the planes.