NEC4 engine can accommodate on the ground or buried radials in
modeling and
calculating vertical antenna parameters and performance.

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

How many weeks of user training does NEC4 require?

Hour many hours of work and imagination are required to enter input
data?

What is the purchase price of the latest version?

Is it legally available to non-USA citizens?
----
Reg, G4FGQ.

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

What! - after 2 days - no reply?

The silence is deafening!
----
Reg, G4FGQ

Hi Tom,

I understand there are measurement issues (and certainly assumption issues
for Rrad). Isn't is fairly certain that increasing the number of radials (of
proper length) until the feedpoint R (at resonance, at the antenna) no
longer drops, is a reasonable approximation of "high efficiency"? The only
issue I see, is determining the target Rrad to compare it to when trying to
"estimate" efficiency.

Are you saying (for example), that the feedpoint R of a 1/4 w vertical
against perfect ground cannot be reliably estimated at 37 ohms? If it can,
then isn't 37/R a measure of efficiency?

Again, I'm thinking of the efficiency of the ground system... I have no way
to look at field strength.

Is it really possible to reduce ground losses to the absolute minimum and
not have a corresponding increase in field strength?

This is starting to turn into "black magic" for me. I can understand
questioning a particular "number" for efficiency based on the simplistic
Rrad/R formula. If the implications go further...indicating there is no
meaning to Rrad/R, then I'm lost.

Perhaps the issue is that it's known how to maximize efficiency, it's just
completely unknown what that efficiency really is, and there is no simple
way to measure it. If that's what your saying, then I understand.

That position does seem to muddy up the "how many radials and of what
length" efficiency info presented in ON4UN's book and referenced in other
texts. They all seem to acccept some sort of accuracy for the Rrad/R formula
with 1/4 w verticals. If I understand you correctly, the formula is rejected
outright as hopelessly simplistic, and of no particular value.

Do I have it now? If so, I'll refrain from using it in the future.

Thanks for the comments.
73,

....hasan, N0AN


wrote in message
ups.com...

hasan schiers wrote:
Not vouching for "degree of accuracy", but here's how I estimate
efficiency:

(Known Rrad/Measured R at X=0) at the feedpoint.

If my Inverted L has a predicted Rrad of 25.9 ohms and I measure the R at
resonance as 29 ohms, the 3.1 ohms is return loss. This would indicate an
approximate efficiency of 89%.

Hi Hasan,

Roy Lewallen and I just measured some ground systems. Actual
measurements using good instruments, not guesses or models.

In one case we had an antenna with four elevated radials that within
measurement error (using lab type gear) had equal signal strength level
as the very same vertical element over 16 buried radials. As I recall
the buried radials had over 60 ohms of base impedance, the six foot
high elevated radials was down around 40 ohms or less.

Over the years I have measured many antenna with very low base
impedance and terrible efficiency, I have measured verticals where
changing the ground system did not change impedance but improved field
strength, and it is very easy to find cases where changes in a ground
system can have MORE efficiency with higher feed impedance without
changing anything but the ground system.

Over simplification of a complex system will often not produce reliable
results. Just look at the results of Reg's progam where it predicts
highest efficiency with very short radials. We all know that doesn't
happen, but the oversimplified program says it does.

73 Tom

"Reg Edwards" wrote in message
...

NEC4 engine can accommodate on the ground or buried radials in
modeling and
calculating vertical antenna parameters and performance.

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

How many weeks of user training does NEC4 require?

Hour many hours of work and imagination are required to enter input
data?

What is the purchase price of the latest version?

Is it legally available to non-USA citizens?
----
Reg, G4FGQ.

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

What! - after 2 days - no reply?

The silence is deafening!
----
Reg, G4FGQ

NEC 4 can be easily used in a few hours with some reading. To
really understand the program would probably require
the equivalent a 3rd year university semester. The program can,
however model an infinite number of antenna designs.

Inputting data is relatively trivial. NEC 4.1 is free, but does require
the purchase of a license from the Lawrence Livermore
National Laboratory. The cost of a license for non-commercial
use is $500.00, and is available to those living outside the USA.
For US residents the license is $300.

For much easier data entry, and error checking etc., GNEC, from
Nittany Scientific makes life a lot simpler -- cost $795.

Frank

I understand there are measurement issues (and certainly assumption
issues
for Rrad). Isn't is fairly certain that increasing the number of radials
(of proper length) until the feedpoint R (at resonance, at the antenna)
no longer drops, is a reasonable approximation of "high efficiency"? The
only issue I see, is determining the target Rrad to compare it to when
trying to "estimate" efficiency.

Are you saying (for example), that the feedpoint R of a 1/4 w vertical
against perfect ground cannot be reliably estimated at 37 ohms? If it can,
then isn't 37/R a measure of efficiency?

Again, I'm thinking of the efficiency of the ground system... I have no
way to look at field strength.

Is it really possible to reduce ground losses to the absolute minimum and
not have a corresponding increase in field strength?

This is starting to turn into "black magic" for me. I can understand
questioning a particular "number" for efficiency based on the simplistic
Rrad/R formula. If the implications go further...indicating there is no
meaning to Rrad/R, then I'm lost.

Perhaps the issue is that it's known how to maximize efficiency, it's just
completely unknown what that efficiency really is, and there is no simple
way to measure it. If that's what your saying, then I understand.

That position does seem to muddy up the "how many radials and of what
length" efficiency info presented in ON4UN's book and referenced in other
texts. They all seem to acccept some sort of accuracy for the Rrad/R
formula with 1/4 w verticals. If I understand you correctly, the formula
is rejected outright as hopelessly simplistic, and of no particular value.

Do I have it now? If so, I'll refrain from using it in the future.

I had always assumed that a NEC model of a perfectly conducting
monopole above a perfect ground would provide the radiation
resistance. For example, considering your antenna of 18.3 m
at 3.62 MHz, the input impedance is 27.5 - j 64.7. The radiation
resistance would therefore be 27.5 ohms. This appears to be
fairly close to your estimate of 25.4 ohms.

Frank

Frank's wrote:
I had always assumed that a NEC model of a perfectly conducting
monopole above a perfect ground would provide the radiation
resistance. For example, considering your antenna of 18.3 m
at 3.62 MHz, the input impedance is 27.5 - j 64.7. The radiation
resistance would therefore be 27.5 ohms. This appears to be
fairly close to your estimate of 25.4 ohms.

If the field strength coordinates were the same for
a perfect antenna model and a real-world antenna
model, would the ratio of the areas under the curves
yield the simulated efficiency of the real-world model?
--
73, Cecil, http://www.qsl.net/w5dxp

"hasan schiers" wrote in message
...
Not vouching for "degree of accuracy", but here's how I estimate
efficiency:

(Known Rrad/Measured R at X=0) at the feedpoint.

If my Inverted L has a predicted Rrad of 25.9 ohms and I measure the
R at
resonance as 29 ohms, the 3.1 ohms is return loss. This would
indicate an
approximate efficiency of 89%.

It seems to me to be a fair approximation. When you have added as
many
radials as possible and watched the input R at the feedpoint (at
resonance)
drop asymptotically toward the predicted or "known" Rrad, your final
"R"
value is used in: Rrad/R. For a perfect ground Rrad = R

I use an MFJ-269 antenna analyzer for the measurements.

Have I gone astray? (aside from my starting value of Rrad, which I
took from
two sources: your rule of thumb formula for Inverted L's, and
ON4UN's Low
Band DX'ing Handbook). Both your formula and ON4UN agree as to the
value of
Rrad for my antenna.

I'll replay to other aspects of your response in another post.

73 and thanks for the new program. As you can tell, I've been
playing with
it. As you can also tell, the implications with respect to length of
radials
required for good efficiency are causing my brain to cramp.

...hasan, N0AN

"Reg Edwards" wrote in message
...

=========================================
Yes Hasan, good agreement. How did you determine
efficiency to THAT degree of accuracy?
=========================================

To Hassan et al,

In all my programs, where antennas are involved, accuracy of results
is usually better than than that needed for the purpose of the
program.

In the case of RADIAL_3 the obvious purpose of the program is to
assist with choosing an economic length and number of radials to be
used with a given test antenna height. It is also educational in that
after reading the introductory notes and using it, the user will have
a better understanding of how radials work.

To summarise, the program tells the user the maximum economic radial
length occurs when the attenuation along it is about 18 to 20dB at the
lowest frequency of use. But where his back yard is not big enough,
even shorter lengths can be quite satisfactory. At HF, where small
standing waves may occur with normal soils, radial lengths can
sometimes be judiciously adjusted to minimise loss.

To increase efficiency when the 20dB limit has been reached it is
necessary to increase the number of radials. And that is subject to
rapidly diminishing returns. As is easily and adequately demonstrated
by the program.

Prediction accuracy can be no better than that of the input data. And
nobody knows what the soil resistivity is in the near field, ie.,
under the antenna, to better than + or - 40 or 50 percent. That's why
NEC4 and the like (or B,L&E) can be no better at predicting results
than RADIAL_3. NEC4 may be highly accurate at predicting radiation
patterns in a hoped-for ideal environment but that is NOT the purpose
of RADIAL_3 which is essentially practical.

If I published the source code hardly anybody would be capable of
making any sense out of it. Some of you old-wives, who imagine you
know more about modelling and programming than I do, would attempt to
ridicule it, thus degrading its usefulness to the ordinary amateur
user. Mud-throwing always sticks.

In the meantime, WW3 is escalating with even greater rapidity!
----
Reg, G4FGQ

Hi Frank,

I think the general question became "can one use this Rrad value in
calculating efficiency". I'm waiting for Tom's response to my last posting.

On the other issue, radial length vs. usefulness, (I tried a diect mail to
you and it didn't make it cuz I forgot to take out the nospam part),

here is what I want to know from NEC-4:

Radial wire is #14 THHN inslulated wire. I approximated it at 2mm. The
antenna wire is 4 mm. For these purposes, you can probably forget that the
wire is insulated.

Now...looking at radial length (assuming 26 radials), and given the
constants I previously provided, how long does a radial in this
configuration have to be, before it is no longer valuable to increase its
length. Tom says he measured significant current in a radial well beyond
where Reg's program says the current had diminished to insignifcant levels.

I would be MOST interested if you can confirm Tom's measurements. If NEC-4
says there is substantial radial current where Reg's program says there
isn't, then that is an important contradiction, putting Reg's model into
question. I'm giving more credibility to NEC-4 (properly used) than I am to
Reg's own design. If, however, we have two sources (one measurement based:
Tom, one model based: NEC-4), that say Reg's theory that radials quickly
approach maximum effectiveness over a MUCH shorter run than has been
previously understood (in moderate to very good soils), that contradict
Reg's algorithim.

Having only looked at conclusions from BL&E, I can't say what their
measurements indicated in terms of radial current vs. length. Ian has
suggested that they did measure the radial current vs length and they concur
with Tom. So, if BL&E and Tom (both empirical), as well as NEC-4 (model
based), all say that important levels of current are present in radials well
beyond where Reg's program predicts, then there's only one conclusion left.
(Unless I'm missing something).

This, to me, is much more interesting stuff than a month long peeing contest
over precipitation static.(which may be rearing its ugly head yet again in
the "double bazooka" thread. God help us!

73, and thanks for your comments and efforts to help me understand what is
going on.

....hasan, N0AN
"Frank's" wrote in message
news:ZO5wg.115459$A8.61548@clgrps12...
I understand there are measurement issues (and certainly assumption
issues
for Rrad). Isn't is fairly certain that increasing the number of radials
(of proper length) until the feedpoint R (at resonance, at the antenna)
no longer drops, is a reasonable approximation of "high efficiency"? The
only issue I see, is determining the target Rrad to compare it to when
trying to "estimate" efficiency.

Are you saying (for example), that the feedpoint R of a 1/4 w vertical
against perfect ground cannot be reliably estimated at 37 ohms? If it
can, then isn't 37/R a measure of efficiency?

Again, I'm thinking of the efficiency of the ground system... I have no
way to look at field strength.

Is it really possible to reduce ground losses to the absolute minimum and
not have a corresponding increase in field strength?

This is starting to turn into "black magic" for me. I can understand
questioning a particular "number" for efficiency based on the simplistic
Rrad/R formula. If the implications go further...indicating there is no
meaning to Rrad/R, then I'm lost.

Perhaps the issue is that it's known how to maximize efficiency, it's
just completely unknown what that efficiency really is, and there is no
simple way to measure it. If that's what your saying, then I understand.

That position does seem to muddy up the "how many radials and of what
length" efficiency info presented in ON4UN's book and referenced in other
texts. They all seem to acccept some sort of accuracy for the Rrad/R
formula with 1/4 w verticals. If I understand you correctly, the formula
is rejected outright as hopelessly simplistic, and of no particular
value.

Do I have it now? If so, I'll refrain from using it in the future.

I had always assumed that a NEC model of a perfectly conducting
monopole above a perfect ground would provide the radiation
resistance. For example, considering your antenna of 18.3 m
at 3.62 MHz, the input impedance is 27.5 - j 64.7. The radiation
resistance would therefore be 27.5 ohms. This appears to be
fairly close to your estimate of 25.4 ohms.

Frank

NEC 4 can be easily used in a few hours with some reading. To
really understand the program would probably require
the equivalent a 3rd year university semester. The program can,
however model an infinite number of antenna designs.

Inputting data is relatively trivial. NEC 4.1 is free, but does
require
the purchase of a license from the Lawrence Livermore
National Laboratory. The cost of a license for non-commercial
use is $500.00, and is available to those living outside the USA.
For US residents the license is $300.

For much easier data entry, and error checking etc., GNEC, from
Nittany Scientific makes life a lot simpler -- cost $795.

Frank
======================================

Thank you very much Frank.
----
Reg, G4FGQ

"Reg Edwards" wrote in message
...

In the case of RADIAL_3 the obvious purpose of the program is to
assist with choosing an economic length and number of radials to be
used with a given test antenna height. It is also educational in that
after reading the introductory notes and using it, the user will have
a better understanding of how radials work.


I understand that Reg, but somewhere in all this an important consideration
is being lost. The issue isn't +/- some questionable percentage of accuracy,
it is the underlying assumption in the model you are using to arrive at the
"much shorter than everyone else's radial length". You have to admit,
predicting 90% efficiency with 5 metre long radials (26 in my example) is
stunning...given BL&E, Tom's measurements, and the yet to be run NEC-4
analysis. We aren't talking small differences here, we are talking NIGHT and
DAY in terms of length.

It really is this simple: Your program predicts neglible current at
distances greater than 5 metres in the example being discussed. Your program
says that any further lengthing is borderline useless. Tom's measurements
completely disagree. BL&E, I am told (I haven't read that section) also
completely disagree. I'm waiting to see what NEC-4 says.

They key is this: are their ANY soil conditions wherein your model of 5
metre long radials (26 of them) will agree with the existing experimental
data, or NEC-4 modeled data? If not, then the "radial as transmission line"
model fails, and should not be used. If one doesn't get the 20 to 25 dB of
attenuation within the radial length limits your program predicts, then the
program is in error and will lead to false conclusions...not just
"inaccuracies", outright major errors. I would love to put in 66 radials 5
metres long and know that they work every bit as well as 66 radials 18
metres long. It would save a lot of money in copper and extra lawn staples.
If, on the other hand, your model is wrong, then a lot of work has been done
for next to nothing. If the purpose of the program is to help in this
process, the program must be trustworthy in its MAJOR assertions.

================================================== =====
We need to know: does the predicted attenuation of current along a radial
wire happen as quickly as you predict? This can be measured. This can be
modeled. That's what makes this fun. Let's find out. Let's see what agrees
with what and what doesn't. Then we can conjecture as to why, and which
approach is to be "believed".
================================================== ======

I'm not denigrating your work. I have all your programs and play with many.
I have found several to be wonderfully useful. However, when something is
called into question, I'm just not religious in scientific matters. Even the
Qur'an says, "Bring your proof, if ye are truthful." (sorry, I couldn't
resist)

73,

....hasan, N0AN

On Fri, 21 Jul 2006 16:24:49 +0100, "Reg Edwards"
wrote:

If I published the source code hardly anybody would be capable of
making any sense out of it.

Hi Reggie,

This posted foolishness was too hard to pass up. It is a superlative
example of the scope of your trolling skills when you troll yourself.
Imagine, writing code so poorly to blame the readers' comprehension
when you yourself are the source of that shoddy effort? This is
classic playing both sides against the middle.

I have to ask, is it written in sonnet form in middle English?

This blighted artwork of yours must come from the bottom of a bottle
in comparison to other code you've written. Of course, lacking that
source, we must accept your own dismal appraisal.

Some of you old-wives, who imagine you
know more about modelling and programming than I do,

And this from someone who claims wholesale ignorance with modeling and
has just admitted to the worst of programming skills. ;-)

would attempt to
ridicule it, thus degrading its usefulness to the ordinary amateur
user.

Reggie, your ridicule has already surpassed all imagined critics.

Mud-throwing always sticks.

Wash your hands before opening that next bottle.

73's
Richard Clark, KB7QHC