Axiom Home Page Forums General Discussion Technical Questions FM Antenna

The length of the antenna serves to make it couple more readily with a specific electromagnetic frequency. Making an antenna longer will effectively "tune" it to a lower frequency, and thus lower its efficiency of selecting the FM band out of the air.

The ideal length of an antenna is for it to be a multiple of the wavelength which you are trying to receive. The wavelength can be found by dividing the speed of light by the frequency. The center of the FM band is 98 MHz, so C / 98 MHz ~= 3m.