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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 |
#2
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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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