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Art wrote:
"Let`s keep it simple. An antenna is just a pendulum with two energy storage tanks per cycle." Not too late for a truth squad to clean up the above, I hope. I infer from the above that Art implies an antenna to be a resonant circuit. Many are resonant because a resonant antenna has no net reactance to impede the signal. But, there is a non-resonant class of antennas. Antennas in this class often have radiating conductors terminated at their far ends in their characteristic resistances (Ro). Traveling waves, reaching Ro which have not yet been radiated are simply absorbed. There is no reflection and no standing waves. Up to 50% of the energy fed to the antenna may be wasted but usually it is somewhat less. 50% waste is a lot, but the directive gain of a typical rhombic may be 50 times according to Fig. 23-18 on page 882 of Terman`s 1955 opus. I`ve used ountless rhombics and attest that Terman got it right. Point is, there`s no pendulum up there, only simple wires carrying RF and they radiate like gangbusters! Best regards, Richard Harrison, KB5WZI |
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