Hangar 9 Piper J-3 Cub 40 ARF - Manual (Page 33)

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Before each flying session, range-check your radio.
This is accomplished by turning on your transmitter
with the antenna collapsed. Turn on the radio in your
airplane. With your airplane on the ground, you should
be able to walk 30 paces away from your airplane and
still have complete control of all functions. If not, don’t
attempt to fly! Have your radio equipment checked out
by the manufacturer.
Range Testing the Radio