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Reg Edwards wrote:
. . . The attenuation due to skin effect and wire inductance along lossy radial wires is rather high. There's negligible current flowing in them at distances greater than 1/4-wavelength at their own velocity. The wires may just as well not be there. . . . I'm afraid your oversimplified model of how radials work has once again led you astray. B, L, & E's measurements show the following: For an 88 degree high vertical, where n is the number of radials, the following fraction of the current at the center is flowing in the radial 1/4 wavelength (at a velocity factor of 0.2, the approximate VF in the radial's environment), from Fig. 42 of their paper: n Fraction 15 0.67 30 0.68 60 0.90 113 ~ 1.0 1/4 *free space* wavelength from the center: n Fraction 15 0.19 30 0.14 60 0.26 [This is a minimum; it rises then drops further out] 113 0.61 " " Note that the results are quite different when the radiator is only 22 degrees high (Fig. 43) -- the resonant effects apparent on the 60 and 113 radial measurements are absent, and the currents decay monotonically. There isn't nearly as much difference between 15 and 113 radials. But with 15 radials, the current 1/4 in-ground wavelength from the center is still about 67% of the current at the center. Again I see evidence that your analysis overlooks the interaction among radials. There's less interaction when there are only a few, but even with 15 your analysis has led you badly astray. And does it account for the considerable differences with different radiator heights? But I've pointed this out to you before yet you keep promoting this myth, so I guess you just don't want to be confused by the facts. If B. L & E, made any errors, they made sure they erred on the safe side regarding numbers. One of their key results is that ". . .the ground system consisting of only 15 radial wires need not be more than 0.1 [free space] wave length long, while the system consisting of 113 radials is still effective out to 0.5 [free space] wave length." Their results agree reasonably well with NEC-4 modeling. But I'm sure glad we've got you to set us straight about how well they did and how they could have improved their methods. You've surely got a clearer perspective, not having been prejudiced by actually reading their paper. Oops, here I am nitpicking again -- pointing out that .67 doesn't equal zero. Roy Lewallen, W7EL Certified Reg's Old Wife and Nit-Picker |
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