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20 kwi 2003 · Following is a series of dipole radiation pattern plots, produced by a popular antenna modeling program. The first plot below shows a dipole at an elevation of two wavelengths above a standard earth ground model. Note the multiple lobes at varying elevation angles above the horizontal.
28 kwi 2023 · A hilltop is often the best choice (and certainly the only choice for SOTA operation!) but sloping ground and drop-offs a wavelength or two distant from the antenna can lower your signal’s elevation pattern dramatically compared to flat ground.
THE HAND-HELD RADIO ANTENNA DILEMMA – 4 – •Adding appropriate lengths of radial material at the base of the antenna provides a ground plane for improved radiation pattern and counterpoise for known RF current return path. (C)2016 - NO1PC, JIM ASPINWALL
An end-fed half-wave (“EFHW”) antenna has a very high feedpoint impedance, often 1000 to 5000 ohms (depending on the diameter). The radiation pattern on the fundamental frequency (where the antenna is 1/2 wavelength) will be similar to the same wire fed in the center as a dipole (but this is not the case on harmonics).
Each electrical type has a specific radiating pattern to be considered when selecting a mobile antenna. For example, the signal radiating from a 1/4 wave antenna is directed more vertically, thus making it ideal in urban environments where buildings might obstruct the signal.
The vertically oriented STL antenna’s -of-8 doughnut shaped radiation pattern figure maximum is in the plane of the loop with -farfield nulls (for small loops) at right angles to the plane of the loop.
•Fed with ladderline and an antenna tuner, this will work all HF bands from its ½ wave frequency on up. •Not concerned with radiation pattern.
