Radiating Efficiency
 

"Frank's" wrote
W7EL tells us that EZNEC doesn't display the surface
wave which obviously contains power. Would that affect
the efficiency using the integration technique?
======================================

The surface or ground wave is the most important fraction of total
radiated power. The correct radiation pattern of a vertical antenna
shows maximum radiation along the ground. Angle of maximum radiation =
0 degrees.

When deducing efficiency, to omit power radiated along the ground from
the hemispherical integration will result in serious error.

( Efficiency by NEC4 ) / ( Efficiency by formula ) = 0.38

I can imagine other losses in addition to loss in the radials but to
have the other losses several times greater is a bit much. Where are
these large losses? Are they in the soil surface - the only other
candidate?
----
Reg.

Radiating Efficiency
 

This thread is getting interesting...

Reg, your point that the resonant radial effects are more pronounced at
higher frequencies makes me think that a small experiment might be in
order.

A 21MHz or so ground mounted monopole with a small radial field would
be a minimal investment in materials to do a BLE style empirical
investigation, at least compared to that at 3MHz. It wouldn't be a
minimal investment in time but might be an interesting experiment.

Given that it would be an epic challenge to measure field strength at a
grid of points on a hemisphere surrounding the monopole, I imagine a
single point field strength measurement would be an acceptable metric?
Thoughts on doing the measurement? I guess BLE would be a good guide
for the empiricist.

Dan

Radiating Efficiency
 

"Reg Edwards" wrote in message
...

"Frank's" wrote
W7EL tells us that EZNEC doesn't display the surface
wave which obviously contains power. Would that affect
the efficiency using the integration technique?
======================================

The surface or ground wave is the most important fraction of total
radiated power. The correct radiation pattern of a vertical antenna
shows maximum radiation along the ground. Angle of maximum radiation =
0 degrees.

When deducing efficiency, to omit power radiated along the ground from
the hemispherical integration will result in serious error.

( Efficiency by NEC4 ) / ( Efficiency by formula ) = 0.38

I can imagine other losses in addition to loss in the radials but to
have the other losses several times greater is a bit much. Where are
these large losses? Are they in the soil surface - the only other
candidate?
----
Reg.

Correct Reg, I had thought the modified RP card
considered ground wave, but it does not. I am working
on a combined integration including the surface wave,
which should provide a more accurate indication of
the overall efficiency. I will also attempt the
analysis of various lengths of radial wires.

Frank

Radiating Efficiency
 

Dan wrote -
A 21MHz or so ground mounted monopole with a small radial field
would
be a minimal investment in materials to do a BLE style empirical
investigation, at least compared to that at 3MHz. It wouldn't be a
minimal investment in time but might be an interesting experiment.

Given that it would be an epic challenge to measure field strength
at a
grid of points on a hemisphere surrounding the monopole, I imagine a
single point field strength measurement would be an acceptable
metric?
Thoughts on doing the measurement? I guess BLE would be a good
guide
for the empiricist.

========================================
The results of such experiments would probably generate far less
interest than BLE's original work and would not be of great use. But
somebody might possibly create a reputation out of it.

To repeat BLE's experiments at HF, and to be of use, would require
measurements to be made over a wide range of frequencies, over various
lengths of radials, over various numbers of radials, over a range of
soil resistivities and over a range of soil permittivities.

Complexity and cost would be enormous. Financial returns would be
relatively small. Who would invest in such a project? How many people
wishing to erect a 28 MHz vertical over a set of radials need more
knowledge than what already exists. Even CB-ers could do it!

It would be far more economic, with a guessed understanding of how
radials work, to write and dedicate a computer program to do the job.
With a little more tidying-up, program Radial_3 would do. And it's
FREE to USA citizens. No licence required! ;o)
----
Reg.

Radiating Efficiency
 

The surface or ground wave is the most important fraction of total
radiated power. The correct radiation pattern of a vertical antenna
shows maximum radiation along the ground. Angle of maximum radiation =
0 degrees.

When deducing efficiency, to omit power radiated along the ground from
the hemispherical integration will result in serious error.

( Efficiency by NEC4 ) / ( Efficiency by formula ) = 0.38

I can imagine other losses in addition to loss in the radials but to
have the other losses several times greater is a bit much. Where are
these large losses? Are they in the soil surface - the only other
candidate?
----
Reg.

Correct Reg, I had thought the modified RP card
considered ground wave, but it does not. I am working
on a combined integration including the surface wave,
which should provide a more accurate indication of
the overall efficiency. I will also attempt the
analysis of various lengths of radial wires.

Frank

Reg, with the antenna we have established as our test model:
All wires #14, monopole 9 m, 36 X 10m radials 25 mm below
ground. Ground parameters Er = 16, resistivity 150 ohm-m.
I have calculated the radiation efficiency including the surface
wave. What is interesting is that the surface wave contributes
very little at elevation angles over 10 degrees.

For 100 W input the total radiated power, not considering
the surface wave, is 31 W. When the surface wave is
included the total radiated power is 36 W.

Frank

Radiating Efficiency
 

"Frank's" wrote
Reg, with the antenna we have established as our test model:
All wires #14, monopole 9 m, 36 X 10m radials 25 mm below
ground. Ground parameters Er = 16, resistivity 150 ohm-m.
I have calculated the radiation efficiency including the surface
wave. What is interesting is that the surface wave contributes
very little at elevation angles over 10 degrees.

For 100 W input the total radiated power, not considering
the surface wave, is 31 W. When the surface wave is
included the total radiated power is 36 W.

==========================================
Frank,

So the missing 64 watts, if not dissipated in the radials must be
dissipated in the soil under the antenna.

To prove something, what is the efficiency when the ground is sea
water. Resistivity = 0.22 ohm-metres and permittivity = 80.

PLEASE CONFIRM THE NUMBER OF RADIALS.

I thought you were unable to model 36 radials. Were you using only 1
radial? With only 1 radial my program makes efficiency = 28 percent.
Which would be satisfactory agreement with your 36 % )

Or did you substitute the radial system with a lumped resistance of 5
ohms which I suggested could be used when estimating efficiency?
----
Reg.

Radiating Efficiency
 

Frank's wrote:
The surface or ground wave is the most important fraction of total
radiated power. The correct radiation pattern of a vertical antenna
shows maximum radiation along the ground. Angle of maximum radiation =
0 degrees.

When deducing efficiency, to omit power radiated along the ground from
the hemispherical integration will result in serious error.

( Efficiency by NEC4 ) / ( Efficiency by formula ) = 0.38

I can imagine other losses in addition to loss in the radials but to
have the other losses several times greater is a bit much. Where are
these large losses? Are they in the soil surface - the only other
candidate?
----
Reg.

Correct Reg, I had thought the modified RP card
considered ground wave, but it does not. I am working
on a combined integration including the surface wave,
which should provide a more accurate indication of
the overall efficiency. I will also attempt the
analysis of various lengths of radial wires.

Frank


Reg, with the antenna we have established as our test model:
All wires #14, monopole 9 m, 36 X 10m radials 25 mm below
ground. Ground parameters Er = 16, resistivity 150 ohm-m.
I have calculated the radiation efficiency including the surface
wave. What is interesting is that the surface wave contributes
very little at elevation angles over 10 degrees.

For 100 W input the total radiated power, not considering
the surface wave, is 31 W. When the surface wave is
included the total radiated power is 36 W.

Frank



Good. Now all you have to do is verify your calculations
experimentally.
73,
Tom Donaly, KA6RUH

Radiating Efficiency
 

Reg, with the antenna we have established as our test model:
All wires #14, monopole 9 m, 36 X 10m radials 25 mm below
ground. Ground parameters Er = 16, resistivity 150 ohm-m.
I have calculated the radiation efficiency including the surface
wave. What is interesting is that the surface wave contributes
very little at elevation angles over 10 degrees.

For 100 W input the total radiated power, not considering
the surface wave, is 31 W. When the surface wave is
included the total radiated power is 36 W.

Frank

Good. Now all you have to do is verify your calculations
experimentally.
73,
Tom Donaly, KA6RUH

You got that right. I need a serious VNA so bad, I can taste it!

73,

Frank

Radiating Efficiency
 

Tom Donaly wrote:
Frank's wrote:
The surface or ground wave is the most important fraction of total
radiated power. The correct radiation pattern of a vertical antenna
shows maximum radiation along the ground. Angle of maximum radiation =
0 degrees.

When deducing efficiency, to omit power radiated along the ground from
the hemispherical integration will result in serious error.

( Efficiency by NEC4 ) / ( Efficiency by formula ) = 0.38

I can imagine other losses in addition to loss in the radials but to
have the other losses several times greater is a bit much. Where are
these large losses? Are they in the soil surface - the only other
candidate?
----
Reg.

Correct Reg, I had thought the modified RP card
considered ground wave, but it does not. I am working
on a combined integration including the surface wave,
which should provide a more accurate indication of
the overall efficiency. I will also attempt the
analysis of various lengths of radial wires.

Frank


Reg, with the antenna we have established as our test model:
All wires #14, monopole 9 m, 36 X 10m radials 25 mm below
ground. Ground parameters Er = 16, resistivity 150 ohm-m.
I have calculated the radiation efficiency including the surface
wave. What is interesting is that the surface wave contributes
very little at elevation angles over 10 degrees.

For 100 W input the total radiated power, not considering
the surface wave, is 31 W. When the surface wave is
included the total radiated power is 36 W.

Frank



Good. Now all you have to do is verify your calculations
experimentally.
73,
Tom Donaly, KA6RUH

That's right. Without verification by direct measurements any program
like this is guesswork.

73 Tom

Radiating Efficiency
 

"Reg Edwards" wrote in message
...

"Frank's" wrote
Reg, with the antenna we have established as our test model:
All wires #14, monopole 9 m, 36 X 10m radials 25 mm below
ground. Ground parameters Er = 16, resistivity 150 ohm-m.
I have calculated the radiation efficiency including the surface
wave. What is interesting is that the surface wave contributes
very little at elevation angles over 10 degrees.

For 100 W input the total radiated power, not considering
the surface wave, is 31 W. When the surface wave is
included the total radiated power is 36 W.

==========================================
Frank,

So the missing 64 watts, if not dissipated in the radials must be
dissipated in the soil under the antenna.

To prove something, what is the efficiency when the ground is sea
water. Resistivity = 0.22 ohm-metres and permittivity = 80.

PLEASE CONFIRM THE NUMBER OF RADIALS.

I thought you were unable to model 36 radials. Were you using only 1
radial? With only 1 radial my program makes efficiency = 28 percent.
Which would be satisfactory agreement with your 36 % )

Or did you substitute the radial system with a lumped resistance of 5
ohms which I suggested could be used when estimating efficiency?


Reg,

The antenna has thirty-six 10 m radials, 25 mm below ground. The input
impedance at 8.07 MHz is 36.3 - j 2.0. I used 0.2 ohm-m for sea water
resistivity as it seems to the accepted standard. The radiation efficiency,
not including the surface wave, is 93.6 %. I can add the surface wave
if you are interested, but it is a little tedious to convert the far field
surface wave, in cylindrical coordinates, to normalized spherical
coordinates; which is the form NEC produces for the sky-wave
components.

Frank