If by "efficiency" we mean the power radiated by the dipole as EM energy
compared to the power applied, what you say simply isn't true.
If we apply 100W to a 70ft dipole made of #14 copper on 80m, about 95W
gets radiated and 5W gets dissipated as I^2R losses in the copper - 95%
efficient! The problem with a 70ft dipole is not its efficiency - that
is very high - it's finding a way of "forcing" 100W into the highly
reactive feedpoint impedance without major losses in the matching
network and/or feedline.
In other words "system" efficiency is likely to be low, but the dipole
efficiency certainly isn't.
On 17/01/2012 18:31, Ken wrote:
> Shortening a half wave dipole, without end loading, significantly
> reduces it's efficiency. A 70' dipole used on 80m without end loading
> is much less efficient of a radiator than the same antenna with end
> loading. And the simplest way to end load such an antenna is to add
> about 30' of wire on each end ;-) Ken WA8JXM
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