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Cecil Moore wrote:
"When the length of a dipole is much, much greater than the diameter of the wire, the antenna will scale appropriately. Yes. An assumption made to ease calculations is that the diameter of the radiator is vanishingly thin. Art`s antenna configuration is something of a mystery to me but I infer that it may be a dipole in which the two lengths of wire have been wound into coils and not extended to their maximum length. Further, my guess is that the dipole is resonant so that it readily accepts energy. Such antenna elements, I believe usually emit energy in the radial mode and resemble the continuously loaded vertical antenna as shown on page 6-28 in the 20th edition of the ARRL Antenna Book. Description of the resonant element includes: "The relationship between length of wire needed for resonance and a full quarter wave at the desired frequency depends on several factors. Some of these are wire size, diameter of the turns, and dielectric properties of the form material to name a few. Experience has indicated that a section of wire approximately one half wavelength long, wound on an insulating form with a linear pitch (equal spacing between turns) will come close to yielding a resonant quarter wavelength. Bill Orr says about the same thing on page 78 of "Vertical Antennas". Continuing from the Antenna Book: "Therefore, an antenna for use on 160 meters would require approximately 260 feet of wire spirally wound on the support." If Art has made a dipole of two such 1/4-wave elements, it should have about a full wavelength of wire which I believe is consistent with his miserly description. Performance of a full wave of coiled wire will be much less than the performance of the same wire stretched out into a straight line at the same height above earth. Best regards, Richard Harrison, KB5WZI |
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