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5

Near Vertical Incidence Skywave (NVIS) is already pretty well defined in both radius and antenna height by definition. The antenna achieves best performance no more than 1/4 wavelength above the ground, and typically reaches receivers 50km-650km (30-400 miles) away. It isn't going to help you out much with receivers 1000-2000km away. Unfortunately there ...


5

Knowing that 1/4λ verticals are known in VHF/UHF applications to have nearly isotropic patterns This is not a valid assertion. A UHF/VHF vertical antenna has > 0 dBi gain (more succinctly a directivity >1) so by definition it cannot have nearly an isotropic pattern. Its primary directivity is toward the horizon at about a 22 degree elevation (although ...


3

If you want NVIS (predominately high-angle radiation, for closer-in stations rather than DX), then you don't want a vertical. Instead, you want something like a horizontal dipole (or inverted-vee), or a horizontal loop. The antenna that that post described was a top-loaded vertical. Its top was connected to the mid-point of the horizontal wire. In that ...


1

If the installation site permits, a dipole antenna in a vertical "Vee" configuration has radiation patterns suitable for NVIS applications -- and can have useful low-angle radiation, as well. The graphic below shows its performance on the 40/80/160m bands for the conditions shown there. Directivity ("gain") is highest in the 40m band, and feedpoint Z is ...


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