AM broadcast antennas with elevated radials: varying the number of radials and their height above ground

Previous computer-modeling studies indicated that four elevated radials may be used in conjunction with an elevated vertical monopole (tower) to produce radiated field strength which is equivalent to that emitted by a similar monopole using 120 buried radials. Inquiries have been received concerning the effect of increasing the number of elevated radials, and/or changing the height of the radials above ground. Analysis shows that there seems to be an optimum number of elevated radials for each height and soil type. Surprisingly, the continued addition of more and more elevated radials eventually produces a reduction in performance. The computer code used for this work was NEC, a “method of moments” program developed at Lawrence Livermore National Laboratory