"Frank" wrote in news:f71Hh.16901$lY6.7593
@edtnps90:


"Wayne" wrote in message
news:5cXGh.391$iD4.256@trnddc06...
When the subject of antenna efficiency comes up, it often involves a
discussion of ground losses on verticals. What about, for example, a
dipole? Could one calculate "power out/power in" by measuring the
VSWR
and declaring that everything not reflected was transmitted? It would
seem more accurate to actually measure power out and power in, but
that
introduces inaccuracies by having to calibrate the setup. Thoughts?

As an example consider a horizontal 75 m dipole, constructed of
#14 AWG copper, at various heights above an average ground.
The radiation efficiency, according to NEC, is shown below:

height 10 ft, efficiency 14%;
height 30 ft, efficiency 54%,
height 90 ft efficiency 82%

The above results do not include the ground wave, which
can be considered lost power. Ground absorption also increases
with proximity to the ground.

Frank,

What is the figure for free space? I suspect closer to 99%. If that is
the case, don't your figures include loss (or absorbption) in rays
reflected by the ground?

Owen