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Old November 13th 07, 04:28 AM posted to rec.radio.amateur.antenna
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First recorded activity by RadioBanter: Jul 2006
Posts: 588
Default question about wire antenna and tuner

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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