Topband: I need help proofing an Inverted L model I made please. 40’ x 143’, four 100’ radials, #14 wire.

WI6X wi6x.73 at gmail.com
Thu Dec 10 10:54:17 EST 2020


> 
> To model radials, we must use Real High Accuracy Ground, with NO connection to Ground. Read the EZNEC manual

Yes! That is what I need to change. Thank you!

Solution:
I was connecting the radials to ground using EZNEC. I need to create the radials just above ground.

Page 90 of the User Manual. 
"Buried radials can be directly modeled only with EZNEC Pro/4 using an NEC-4 calculating engine (see Buried Wires). With EZNEC, EZNEC+, and EZNEC Pro/2 they have to be simulated.”

Buried radials with EZNEC have to be simulated. “...model buried radials by substituting radials just above the ground surface. This does a moderately good job of predicting the ground system efficiency as well as whatever pattern modification results from the radial system. With this approach, the High Accuracy Real ground type must be used. See Connecting to High Accuracy Ground for more information.”

Page 127 of the User Manual
"With program types other than EZNEC Pro/4 the best way to approximate a buried radial system is by creating horizontal radials just above the ground, and make the "ground" connection to the radials. A height of between about 1/100 and 1/1000 of a wavelength is suitable, but in any case no less than several wire diameters. If a low impedance connection is required, make the radials about a quarter wavelength or odd multiples long, and avoid lengths approaching a half wavelength or multiples. These aren't free space wavelengths, however, but wavelengths for a wire at the radial height. A half wavelength for a wire very close to the ground will be less than in free space, though. You can determine the wavelength by modeling a dipole at the height of the radials and adjusting its length until it's resonant. Be sure you're seeing the lowest (series) resonance, which for very low wires will occur with a dipole length somewhat less than a free space half wavelength. The best radial length will be about half the resonant dipole length. 
Radials can easily be constructed using EZNEC's automated radial creation feature. Above ground radials will show resonant effects more sharply than buried radials, but will provide a reasonable approximation of a buried radial system."



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