On 5 Mar, 12:58, Owen Duffy wrote:
"Wayne" wrote innews: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

The reason for focus on ground loss on (HF) verticals is that, unless you
have taken extreme measures with a ground system, ground loss dwarfs
other losses and in that case dominates considerations of efficiency.
Next would come loading coils.

dipole? Could one calculate "power out/power in" by measuring the

Half wave dipoles made from practical materials are usually very high
efficiency, losses commonly range in the area of 1% to ~3%. Loading coils
are a significant loss element in loaded dipoles. Some folk (eg ARRL)
have a mind that linear loading (folding the conductors back on
themselves) is lossless, but my analysis of the Cobra shows that is not
the case, seehttp://www.vk1od.net/cobra/index.htm. Even other lengths
of unloaded dipoles may be very efficient, but the feedpoint impedance
may drive huge losses on the feedline and so whilst the radiator is
efficient, the antenna system may be inefficient.

Components of an antenna system interact with each other in a complex
way, and it is important to analyse the entire antenna system (radiator,
earth, transmission line, balun, ATU etc) to obtain a correct
understanding of how the system works overall.

VSWR and declaring that everything not reflected was transmitted? It

Roy has already explained to you that you have some misconceptions about
VSWR, "forward power", and "reflected power".

There has been another raging discussion here about what happens to the
"reflected power", it isn't necessarily, and isn't usually lost (ie
dissipated as heat), but as I have stated above the feedpoint impedance
may drive huge losses on the feedline, it may also reduce the power
available from the transmitter and may reduce the transmitter efficiency.

would seem more accurate to actually measure power out and power in,
but that introduces inaccuracies by having to calibrate the setup.
Thoughts?

In terms of efficiency on the larger scale, a significant of power is
lost in the process of reflecting some rays from real ground.

Owen

Oh my !!!!!!

My dipole has a 1:1 swr. Neigbour next door puts a fence around his
lot.
My SWR goes to 3:1. No problem, swr has no connection to efficiency
somebody said so everything is O.K.
Except what is the definition of efficiency? Radiation resistance,
effective use of the radiation, cancellation of radiation?????
You better get that bit straightened out before you enlarge and
expouse
other statements which may cancel the legitamacy of your response.
Another point to ponder on the other side. At what point can we
separate the formation of radiation, at the radiation surface, the
beginning of the near field the exit from the near field? If you are
going to talk efficiency
then you must have a closed border around which equilibrium is
determined
which brings us back to Gauss. Pretty neat!!
Art
Art