Evaluation methods for helical and spiral VHF/UHF satellite antennas

A helix antenna and a cavity-backed spiral antenna are built and tested for use in the 240-320 MHz satellite frequency band. Two methods are examined for quickly and inexpensively verifying the performance of these antennas. First, an outdoor pattern measurement is performed that makes use of the fundamental properties of directivity to avoid the need for an anechoic chamber and a calibrated reference antenna. Second, the antennas are used directly to make a series of measurements of the power received from a satellite to verify performance.