Vertical transmission from catenaries

Rhombic or delta antennas are frequently used, e.g. for ionospheric sounding, because of their large gains. Normally, in such antennas, the suspended wire forms a catenary that substantially changes the transmitted electric field. It is therefore important to investigate the vertical transmission from catenaries in order to obtain a better antenna design, suitable for real conditions. We analyze the performance of resistance-terminated traveling-wave aerials, with real shapes and heights. Analytical formulas for the electric field transmission in vertical direction are deduced for such aerials with one and two catenaries. A perfect, flat ground for the reflection is assumed, and the attenuation along the wire is neglected. It is shown that aerial catenaries produce shallower gaps in the electric field intensity compared to straight-wire constructions. Representative calculations are presented for the ionosonde transmit antenna at the RMI Geophysical Centre in Dourbes, Belgium.