Anyone know?

[BrianG]

Extending an antenna might help, but most antennas are tuned to a specific frequency bandwidth. If you "detune" the antenna too much by lengthening it or shortening too much, you could actually reduce the range. If you want to extend it, I'd extend it no more than 10% of it's current length. If that's too short, you can double it. Lengths in between will probably be detrimental.