Eznec

Elevated radial systems A number of people have showed an interest in modeling systems of radial wires placed at very low heights above ground. A system of very low wires can be used to simulate the performance of buried radials. Extensive experiments were done comparing various modeling codes, resulting in the following guidelines: 1. The minimum recommended height for modeling ground radial systems is 1E-4 (0.0001) wavelength, or the diameter of the vertical wire, whichever is greater.

2. No special techniques are required if the radials are at a height of at least 0.001 wavelength and at least the diameter of the vertical wire. Ordinary segmentation can be used. Even stepped diameters don't require special attention in this situation. This height is recommended for simulating buried radials or radials placed on the surface of the ground.

3. If the radials are between 0.001 and 0.0001 wavelength high, segment length tapering should be used (see p. 48).

The minimum segment length should be made equal to the height of the radial system. The default maximum is adequate. When prompted for the minimum, maximum segment lengths in the tapering process, enter '#,' where # is the height of the radial system above ground in current units.

When placed on such a short wire, the source must be surrounded by equal-length segments. After tapering, combine the source wire and the one above into a single wire with 3 segments, then move the source to the center of this wire. If, for example, the original vertical wire was wire 1, with end 1 at the bottom (as in example file ELEVRAD1.EZ), first taper all wires. Then select end 2 of wire 1 and enter 'W2E2' to make its coordinates the same as end 2 of wire 2. Change the number of segments of wire 1 to 3. Then delete wire 2. Finally, move the source to the center of wire 1. The result should look like ELEVRAD2.EZ. I don't know of any good experimental measurements of the skywave field strength from verticals with elevated radial systems. There are a few ground-wave measurements. According to EZNEC and a more advanced code (NEC-4, which can't be incorporated into EZNEC due to use restrictions), the sky wave 31