An antenna that is tuned to a frequency will perform better than a untuned antenna. Here is a formula that will let you tune an antenna for perfect reception and transmission if needed. Take your receive frequency, lets say the middle of the FM band 100 Mhz and divide into 468 then divide it by 2, this will be a perfect 1/4 wave antenna. 468/100=4.68/2=2.32 feet or 27.84 inches.Cut in half if you are. Antenna size is specific to a frequency or frequency range its designed for. You want to keep the length a relative multiple or ratio of the bandwidth.