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Old September 4th 09, 06:27 PM posted to rec.radio.amateur.antenna
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Default ART vs. W8JI

On Sep 4, 8:54*am, Cecil Moore wrote:
Richard Fry wrote:
If the power applied to the full wave dipole was 1.6 dB less than
applied to the 1/2-wave dipole, then their measured peak fields would
be identical. *But that is not a power reduction of one half (3 dB),


Increase the length of the one wavelength dipole to a
1.25WL EDZ and the maximum gain indeed does increase by
~3dB over a 1/2WL dipole. Consider that the highest gain
for a single-wire antenna with a figure-8 radiation pattern
occurs with a feedpoint impedance of ~175-j1000 ohms, i.e.
the antenna wire, by itself, is *non-resonant*. A parasitic
element 1.25WL long would have a negligible effect on an
antenna system. :-0

Consider that if one disconnects the feedline from a 1/2WL
center-fed dipole, the two remaining 1/4WL wires separated
by an insulator are *non-resonant*. Breaking guy wires into
1/4WL separated by insulators is one way of avoiding
resonance. :-)
--
73, Cecil, IEEE, OOTC, *http://www.w5dxp.com


Cecil you misunderstood what I was saying .
When you use a fractional WL then some of the wire cannot radiate,
thus the impedance is reduced from that of a full WL. Power is still
I sqd R Cos phi. where there is a varience. with the R in this case of
a approx 1/2. Gain is not involved, only energy dissipated.
Regards
 
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