Jimmie D reported Roy Lewallen to write:
"There is no direct way to measure the total power being radiated other
than sampling the field at many points in all directions and
integrating."

That sounds right to me. An approximation is sometimes made by taking 36
samples of field strength in volts per meter at 10-fegrees of azimuth
intervals at the same distance from the central antenna system. Each of
these sample values is squared and the sum of these squared samples is
divided by 36, the number of samples, to get their average. The square
poot of this quotient is then the average field strength at that
distance from the antenna. A true average signal strength should be the
same as the value an isotropic antenna would radiate at a given
distance.

Knowing the field strength, one could calculate the watts per square
meter of the envelope of radiation at a given distance and total the
watts per square meter of all the squares to get the total power being
radiated.

Since 1960, I`ve used the Bird wattmeter satisfactorily to get the total
power being delivered by the transmitter and radiated by the antenna. It
should be the same if the transmission line and antenna have low losses.
It is simply the difference between the forward power indication and the
reverse power indication. Many lines and antennas have very high
efficiencies.

Best regards, Richard Harrison, KB5WZI

(Richard Harrison) wrote in news:10571-
:

Jimmie D reported Roy Lewallen to write:
"There is no direct way to measure the total power being radiated other
than sampling the field at many points in all directions and
integrating."

That sounds right to me. An approximation is sometimes made by taking
36
samples of field strength in volts per meter at 10-fegrees of azimuth
intervals at the same distance from the central antenna system. Each of
these sample values is squared and the sum of these squared samples is
divided by 36, the number of samples, to get their average. The square
poot of this quotient is then the average field strength at that
distance from the antenna. A true average signal strength should be the
same as the value an isotropic antenna would radiate at a given
distance.

Is that true?

Firstly you seem to assume that your 36 samples around the azimut circle
adequately fulfill Roy's "sampling the field at many points in all
directions", surely he mean't all elevation angles as well as all azimuth
angles.

Secondly, your suggestion that the average field strength (presumably for
a 100% efficient antenna) at zero elevation is the same as for an
isotropic antenna at the same distance seems to preclude the antenna
having directivity in the elevation dimension.

Owen

"Wayne" wrote in
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

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, see http://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

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

art wrote:

. . .

Except what is the definition of efficiency? Radiation resistance,
effective use of the radiation, cancellation of radiation?????

The definition of efficiency with respect to antennas is very well
defined, understood, and agreed upon in all the amateur and professional
literature. Virtually every text and professional paper uses an
identical definition, and that is: the fraction of the power applied to
an antenna which is radiated. I know that Art often uses the term to
mean several other different things which I don't believe he's ever
clarified (at least not that I could understand), so some caution should
be used in making assumptions about its meaning when used in this newsgroup.

. . .

Roy Lewallen, W7EL

On 5 Mar, 14:47, Roy Lewallen wrote:
art wrote:

. . .

Except what is the definition of efficiency? Radiation resistance,
effective use of the radiation, cancellation of radiation?????

The definition of efficiency with respect to antennas is very well
defined, understood, and agreed upon in all the amateur and professional
literature. Virtually every text and professional paper uses an
identical definition, and that is: the fraction of the power applied to
an antenna which is radiated. I know that Art often uses the term to
mean several other different things which I don't believe he's ever
clarified (at least not that I could understand), so some caution should
be used in making assumptions about its meaning when used in this newsgroup.

. . .

Roy Lewallen, W7EL

Exactly, whose definition, whose limitations, by what authority?
The term efficiency is universal in its intent and is measered by the
terms imposed. You did not pose any limitations of any kind. The word
efficiency is not identified with potato's in one part of science and
carrots in another part of science. It has true meaning in all
sciences relative to the context that is used. The number of books you
have is not a deciding factor tho it probably had a hand in you
ASSUMPTIONS
Art

"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.

Regards,

Frank

"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

"Owen Duffy" wrote in message
...
"Frank" wrote in news:f71Hh.16901$lY6.7593
........
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

Correct Owen. NEC shows 97.3% for free space, and 100 %,
as expected, with perfect conductors. Certainly the loss does
include absorption of the reflected rays. As mentioned before, in
previous threads, it is very tedious to determine what percentage
of the "Loss" is due to ground wave radiation. One of these
days I will write the code necessary to compute the actual
TRP including ground wave.

Frank

Frank wrote:

Correct Owen. NEC shows 97.3% for free space, and 100 %,
as expected, with perfect conductors. Certainly the loss does
include absorption of the reflected rays. As mentioned before, in
previous threads, it is very tedious to determine what percentage
of the "Loss" is due to ground wave radiation. One of these
days I will write the code necessary to compute the actual
TRP including ground wave.

That capability is already built into NEC, as the average gain calculation.

Roy Lewallen, W7EL