Broadband trapped multiple-wire antennas

A vertical monopole consisting of 13 wires and 39 trap circuits, as a 10:1 scale model of an antenna for the 2- to 30-MHz band was built and tested. In the range from 18 to 600 MHz, the measured VSWR referred to160 \Omegaexceeds 4:1 in only a few relatively narrow frequency ranges. The results agree well with a simple design theory, which is based on Schelkunoff's transmission-line equivalence. My belief is that refinement of this approach may lead to antennas that are efficient and reasonably well matched over three or four octaves.