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I originally wrote:
Consider using an UNBALANCED, open-wire line. It would consist of three wires fairly close together with uniform spacing between them. The center wire is "hot" and the outer two are "ground". Cecil, W5DXP asks: Hi Jim, what would be the range of Z0's possible with this configuration? Jasik has a formula for this type of line: Zo = (207/sqrt(epsilon))*(log(1.59*(Dist/dia))) where Zo is in ohms, epsilon is relative dielectric constant of surroundings (=1.0 in this case), sqrt is the square root function, log is the base-10 logarithm function, Dist is the distance between the center wire and one of the outside wires and dia is the diameter of the wires used, Dist and dia being in the same units. Setting dia=0.116 inches (#10 AWG stranded wire) and varying Dist gives: Dist = 1.0 inch ............ Zo = 235 ohms Dist = 2.0 inches .......... Zo = 297 ohms Dist = 4 inches .......... Zo = 360 ohms Dist = 10 inches .......... Zo = 442 ohms The trade-off would be between the desireable high impedance from wide spacing and leakage suppression from close spacing. Dist=4 inches looks about right. Although I haven't tried it, my guess is that common electric- fence hardware would be adequate for supports and insulation, but the conductors should be copper (and #10 gauge). Stacking the conductors vertically should simplify the mechanical aspects and possibly partially suppress sky-wave leakage from the line. Jim, K7JEB Glendale, AZ |
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