VU2NSB OmniDX Antenna series is a very special set of monoband antennas that have been designed from the core keeping in mind the optimal radiation lobe pattern characteristics needed for good DX as well as medium range operation on HF bands. Unlike Yagis, Quads, etc, where the antennas structure determines the expected radiation patterns, we worked the other way round. We first determined the desired radiation pattern that was needed and then designed the antenna structure required to meet our objective.
VU2NSB OmniDX antenna consists of six vertically polarized co-phased collinear radiators with integral counterpoise mounted on a boom. Each radiator is driven with a unique proprietary phase shift paradigm using coaxial cable phasing harnesses. The feed-point of the array produces an impedance ideal for matching a 50 ohm coax transmission line with SWR below 1.5:1. The antenna also has excellent radiation efficiency with a forward gain of 14 dBi and Relative Directivity Factor (RDF) greater than 15dB.
The objective was to design an antenna that would have a good forward gain at low and medium radiation takeoff angles, yet provide an ability to listen all around in 360 degree azimuth plane. The main forward lobe is a flattened, front peaking, fish belly shaped lobe to achieve a broad azimuth view. It also has a significantly broadened back lobe including two rear slanting side lobes. Two more upturned side-lobes are produced for listening to short/medium distance stations in those directions.
To summarize, VU2NSB OmniDX antenna series are designed to allow very good DX in the forward direction, not by producing brute power gain but by optimizing the lobe patterns. At the same time, you will not miss out on the stations operating from other directions. The stations on the back side will never go unnoticed.