Why A "rubber duck" is a physically shortened antenna, usually a helically wound coil, that is electrically loaded to look resonant to the radio. Shortening an antenna lowers its radiation resistance and raises losses, so much of the transmitter power is dissipated as heat in the loading coil and matching rather than radiated. A full-size quarter-wave whip radiates a much larger fraction of the power fed to it, so it both transmits and receives better.