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Old February 16th 10, 06:05 PM posted to rec.radio.amateur.antenna
Cecil Moore Cecil Moore is offline
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First recorded activity by RadioBanter: Aug 2006
Posts: 572
Default Zepp antenna the ultimate OCF?

On Feb 15, 3:25*pm, Michael Coslo wrote:
Is this the ultimate waaayyy off center dipole? I'm assuming the
feedline radiates a LOT.


Historically, a Zepp has been defined as a 1/2WL wire end-fed with
1/4WL of parallel feedline, a single-band antenna. MFJ sells such HF
antennas modified for 50 ohm feed. The 1/2WL end-fed wire has a very
high feedpoint impedance thus minimizing the current at the feedpoint
and minimizing the absolute magnitude of imbalance (but not the
percentage of imbalance). For instance, the current for 100 watts into
a 5000 ohm feedpoint impedance is 141 ma., a magnitude less than the
1.41 amps into 50 ohms for the same 100 watts. Seems to me, the low
current at the feedpoint, which can be considered to be common-mode,
ensures a current minimum for both differential and common-mode
standing waves.

P.S. A Double Zepp is the same thing as a 1WL center-fed dipole.
--
73, Cecil, w5dxp.com