Radiating Efficiency
 

Frank, the reason I asked what the efficiency is when using sea water
was to prove your own efficiency calculations.

With sea water the efficiency should be very near to 100 percent. You
get 93% WITHOUT taking the surface wave into account. To make youself
happy you could include the surface wave.

Program Radial_3, with sea water, makes efficiency 98 percent which
I'm confident is near enough correct. Most of the loss is in the HF
resistance of the 14-gauge antenna wire.

================================================== ======

It's beginning to look as though the oft-quoted formula -

Efficiency = Rrad / ( Rrad + Rloss )

is very much in error. This formula is quoted in all the ARRL books
and other learned magazines. I will correct my program to agree
better with NEC4 even though the absolute value of efficiency is not
important and is used only as an indication to maximise effectiveness
of the radial system.

I await your experiments to determine the impedance Zo of ONE radial
wire and the approximate distance at which it occurs.

You can do N = 36 radials at a later date.
Thank you very much.
----
Reg.

Radiating Efficiency
 

On Thu, 27 Jul 2006 19:01:14 +0100, "Reg Edwards"
wrote:

It's beginning to look as though the oft-quoted formula -

Efficiency = Rrad / ( Rrad + Rloss )

is very much in error.

Hi Reggie,

In fact the entire enquiry has justified it. How do you come to the
opposite conclusion?

73's
Richard Clark, KB7QHC

Radiating Efficiency
 

"Reg Edwards" wrote in message
...
Frank, the reason I asked what the efficiency is when using sea water
was to prove your own efficiency calculations.

With sea water the efficiency should be very near to 100 percent. You
get 93% WITHOUT taking the surface wave into account. To make youself
happy you could include the surface wave.

Program Radial_3, with sea water, makes efficiency 98 percent which
I'm confident is near enough correct. Most of the loss is in the HF
resistance of the 14-gauge antenna wire.

================================================== ======

It's beginning to look as though the oft-quoted formula -

Efficiency = Rrad / ( Rrad + Rloss )

is very much in error. This formula is quoted in all the ARRL books
and other learned magazines. I will correct my program to agree
better with NEC4 even though the absolute value of efficiency is not
important and is used only as an indication to maximise effectiveness
of the radial system.

I await your experiments to determine the impedance Zo of ONE radial
wire and the approximate distance at which it occurs.

You can do N = 36 radials at a later date.
Thank you very much.

Reg,

The efficiency, including the surface wave, is 96%. There is also
a 2% copper loss. With perfect conductors the efficiency
would then be 98%. All figures from 100 W input.

I have not forgotten the single radial computation.

Frank

Radiating Efficiency
 

Frank,

The efficiency formula is incomplete rather than being in error.

In the case of radial systems it could be something like -

Efficiency = Rr / ( Rr + Rradials + Rsoilsurface ) .

When soil resistivity becomes very small, efficiency approaches 100
percent and the error when compared with NEC4 reduces to zero. The
error is therefore a function of soil resistivity.
----
Reg.

Radiating Efficiency
 

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

When 2 + 3 + 1 = 6 inches, do you always have to verify it with a
wooden ruler? ;o)
----
Reg.

Radiating Efficiency
 

"Reg Edwards" wrote in message
...
Frank,

The efficiency formula is incomplete rather than being in error.

In the case of radial systems it could be something like -

Efficiency = Rr / ( Rr + Rradials + Rsoilsurface ) .

When soil resistivity becomes very small, efficiency approaches 100
percent and the error when compared with NEC4 reduces to zero. The
error is therefore a function of soil resistivity.
----
Reg.

Sounds reasonable Reg.

Frank

Radiating Efficiency
 

Reg Edwards wrote:
Frank,

The efficiency formula is incomplete rather than being in error.

In the case of radial systems it could be something like -

Efficiency = Rr / ( Rr + Rradials + Rsoilsurface ) .

When soil resistivity becomes very small, efficiency approaches 100
percent and the error when compared with NEC4 reduces to zero. The
error is therefore a function of soil resistivity.
----
Reg.



So, Rloss = Rradials + Rsoilsurface.

The components of Rloss change depending on the antenna being studied.

But, Efficiency is still % = (Rr/(Rr + Rloss))*100

/s/ DD

Radiating Efficiency
 

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

========================================

When 2 + 3 + 1 = 6 inches, do you always have to verify it with a
wooden ruler? ;o)
----
Reg.



2 + 3 + 1 doesn't ever equal 6 inches. 2 inches + 3 inches + 1 inch
does, however, and if you build something that is
2 inches + 3 inches + 1 inch, you'll most likely verify it with
a ruler just to see how close you got.
73,
Tom Donaly, KA6RUH

Radiating Efficiency
 

I await your experiments to determine the impedance Zo of ONE radial
wire and the approximate distance at which it occurs.

You can do N = 36 radials at a later date.
Thank you very much.

Reg, I started to do an analysis of a single radial monopole.
Beginning with a 1 meter length radial I compared the results
with "radial_3". There is such a huge discrepancy between
the programs I wondered if I had made an error someplace.

Just to confirm the antenna dimensions: 9 m monopole,
with a 1 m radial, 25 mm below ground. All wires # 14 AWG,
and the test frequency 8.07 MHz. Ground Er = 16,
resistivity 150 ohm-meters.

"radial_3":
Antenna input Z = 34.21 - j 26.2, and;
radial input Z = 82.7 - j 62.3.

"NEC 4.1":
antenna input Z = 137.8 - j 81.8, and;
radial input Z = 101.4 - j 79.1.

Interesting to note that the input impedance determined
by radial_3 is very close to an ideal monopole above
a perfectly conducting ground.

Frank

Radiating Efficiency
 

Frank, I am not interested is what happens at very short lengths or
what Radial_3 makes of it.

To determine Zo, start around 10 metres.

If very little happens to input impedance between 10 and and 15 metres
then you already have Zo = Zin = Ro + jXo.

Neither am I interested in efficiency or antenna input impedance..
The problem of Efficiency has already been sorted out.

All I wish to know is Zin = Zo of a single radial, at various lengths
greater than about 10 metres, of diameter = 1.64mm, depth = 25mm,
ground resistivity = 150 ohm-metres, permittivity = 16, at a frequency
of about 8.07 MHz.

That is the input impedance of one radial when the attenuation is
about 20dB or greater.

To summarise, I wish to know Zo = Ro + jXo for one radial.
----
Reg.