Antenna elements for improved shipboard HF direction-finding

The situation of shipboard DF antennas is briefly analysed. It is shown that DF errors are worst within the HF range, and then especially to port and starboard. It is shown that this region can be covered by a parallel loop arrangement which must be kept `blind¿¿ to the main reradiating structures in addition to the conventional crossed loop DF. Theoretical considerations prove that all structures in a ship´s symmetry plane and an idealised ship´s hull no longer create bearing errors. Unsymmetrically placed components, which continue to affect the parallel loop, turn out to produce merely a very smooth error curve, which can easily be compensated by computer-stored correction tables during the evaluation process. Polarisation errors, which appear when direction-finding with a crossed loop, are shown to be at a much lower level when using a parallel loop.