[TowerTalk] Dipole fed with balanced line?
Steve Hunt
steve at karinya.net
Tue Jan 17 10:51:59 PST 2012
Ken,
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.
73,
Steve G3TXQ
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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