The Double Zepp (Doublet) antenna is a classical antenna in our series of HS4 Legendary Multiband Wire Antennas. It covers 7 bands, 10-12-15-17-20-40-80m. Unlike typical antennas, this is a non-resonant antenna. The performance characteristics are quite outstanding. The antenna consists of symmetrical horizontal radiating elements being driven via an open wire ladder line or a slotted line. Such transmission lines not only ensure very low transmission line (TL) losses but also its pre-determined and well defined length is crucial as it plays a vital role in determining the SWR by acting as a frequency dependant TL transformer. However, the principle of a Double Zepp also utilizes various other complex methods of taming the SWR to workable limits.
This antenna needs to be driven trough an antenna tuner and also needs a broadband impedance transforming Balun. The overall gain on all bands is good with adequate low angle radiation for great DX. This antenna is deployed at a height of 12m (40 ft.) above average quality ground and the design accounts for ground absorption losses, antenna wire insulation dielectric losses, other structural losses, etc.
The most important aspect to keep in mind is that the radiation lobe patters vary from band to band and may not have maximum radiation in the forward direction of orientation on all bands. On some bands one might find that there could be a null in the forward direction but a nominal swing of the antenna away from this null will bring up the gain. The owner of this antenna will need to find the optimum direction of the radiation lobe on each band either by experimentation during the process of familiarizing the antenna characteristics or may refer to the exhaustive set of specifications with graphics and gain map given below... Happy DXing!