Calculating Antenna Length for FM Broadcasting

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Using a properly tuned antenna is essential for micropower broadcasting on the FM band. An antenna that is not properly tuned will not pass along your transmitter's power as efficiently as it could - and this leads to a general degradation of signal coverage.

Fortunately, calculating the precise length of your antenna is pretty easy to do if you follow these three steps. Get a calculator to help with the math:

1. To determine the wavelength of your signal in inches, divide 11811 by your transmitter's frequency in megahertz (MHz). 

2. Multiply the answer from #1 by the fraction of wavelength of your antenna's design (most antennas are 1/2 (.5) or 1/4 (.25)  wave; the popular Comet is a 5/8 (.625) wave antenna). 

3. The answer from #2 is the length of your antenna in inches. 

ALWAYS fine-tune your antenna using a properly-calibrated SWR meter for maximum antenna efficiency! A perfect SWR match is 1:1; in the real world, you should be satisfied with any SWR of 1.5:1 or less.