Performance of a non-rotating direction-finder for automatic radio tracking

The expense of gathering location data on birds and other wildlife using traditional techniques often discourages observers from obtaining frequent samples. To automate the direction-finding (DF) task important in radiolocation, a prototype system based on a circular array of antennas with no moving parts is described. It can operate continuously and rapidly, recording bearings on multiple radio transmitters. Using fewer than 10 pulses of a radio transmitter, DF stations report bearings. Static DF accuracy in open country was comparable to reported accuracy of manual methods in various habitats; performance in worst-case, real-life tests with small transmitters on wild passerines in secondary growth was poorer. In static tests, habitat features near the transmitter proved to be important in measurements using ''dither.'' Such low-maintenance devices have advantages, especially for continuous recordings, for simultaneous localization of many subjects, and when access to a site is difficult.