Winding the Rx antenna is an old aeromodelling trick, but results are sort of unpredictable because of the many factors involved (servo installation, wiring, etc..)
Here you'll find a well documented article about lenghtening/shortening Rx antennae:
http://www.rc-cam.com/ant_exp.htm
Anyway this should become critic only in airplane rc, in our tanks we hardly need more than an effective 20-30m range (around 60'-90') and you can easily reach this range with virtually any lenght and type of Rx antenna

Cheers