Low-angle Elevation Gain of a 1/4-wave Vertical Monopole
 

Richard Clark wrote:
You have the cogent characteristics of my model, now demonstrate your
suggestion by showing its incorrect feature(s).

You gave no characteristics of the NEC construction and settings for
your model (cogent or otherwise), as I did for mine. You only stated
the results you say you got.

Even Roy Lewallen wrote that he will look into the correspondence of
my EZNEC solution with the FCC value for those conditions -- which Roy
probably wouldn't choose to do if there was good agreement between
them, or my "near field" model was obviously incorrect to him.

RF

Low-angle Elevation Gain of a 1/4-wave Vertical Monopole
 

On Thu, 27 Nov 2008 13:39:46 -0800 (PST), Richard Fry
wrote:

You gave no characteristics of the NEC construction and settings for
your model (cogent or otherwise), as I did for mine.

On Wed, 26 Nov 2008 11:41:04 -0800 (PST), Richard Fry wrote:

The near-field analysis of EZNEC for radiation in the horizontal plane
at a point 1 km from a 1/4-wave monopole having two ohms in series
with a Mininec r-f ground, while radiating 1 kW over an earth
conductivity of 8 mS/m is shown as 72 mV/m.

When I observe the operational characteristics of EZNEC (you report
you use it above) AND I observe that it does not offer a Near Field
analysis for Mininec r-f ground (as you report you use above) THEN I
have to wonder how you arrive at a figure of 72 mV/m (as you report
you obtained above). Other than version differences or updates in the
program that supercede mine, I rely on the advice found in the Help
manual provided:
Near field analysis is disabled when MININEC-type ground is selected.
...Use some other ground type for near field analysis.

Your failure to heed this advice seems consistent with your repeated
ignorance of EZNEC's capacity to perform Near Field Analysis. Also
consistent is the complete absence of radials in your model - the
hallmark (cogent) research of BL&E's "Ground Systems as a Factor in
Antenna Efficiency." This consistency propagates into your near field
report - where did you get
is shown as 72 mV/m.
from?

Did you achieve this valuation through a novel upgrade feature found
in EZNEC 5? If so, I bet the help entry still suggests that mininec
type ground is not preferred (and that you ignored that commentary
too). The differences in models to replicate BL&E results well
illustrates this for any version issue you may reveal.

73's
Richard Clark, KB7QHC

Low-angle Elevation Gain of a 1/4-wave Vertical Monopole
 

On Nov 27, 10:46*pm, Richard Clark wrote:

When I observe the operational characteristics of EZNEC (you report
you use it above) AND I observe that it does not offer a Near Field
analysis for Mininec r-f ground (as you report you use above) THEN I
have to wonder how you arrive at a figure of 72 mV/m (as you report
you obtained above). Other than version differences or updates in the
program that supercede mine, I rely on the advice found in the Help
manual provided:

Near field analysis is disabled when MININEC-type ground is selected.
...Use some other ground type for near field analysis.

Obviously, near-field analysis was not disabled by/in EZNEC for my
model definition. The surface-wave value of 72 mV/m at 1 km for 1 kW
of radiated power is shown in the screen clip I linked to in my first
post about this.

Also consistent is the complete absence of radials in your model - the
hallmark (cogent) research of BL&E's "Ground Systems as a Factor in
Antenna Efficiency."

The r-f loss of the radial system is accounted for in my model by the
two ohms of resistance inserted between the base of the monopole and
ground, as shown in my screen clip. This two ohms is approximately
the r-f loss of a set of 120 buried radials, each 1/4-wave in physical
length.

The peak gain of the elevation pattern in my model (see my screen
clip) is consistent with such a ground loss and the selected ground
conductivity, so this approach appears to be valid.

Hopefully Roy Lewallen will weigh in, as he has time, to comment on
the methods and results of our two analyses -- although probably Roy
will need more details about your model construction than you have so
far been willing to provide.

I will be content to let the chips fall where they may.

RF

Low-angle Elevation Gain of a 1/4-wave Vertical Monopole
 

On Fri, 28 Nov 2008 03:53:00 -0800 (PST), Richard Fry
wrote:

Near field analysis is disabled when MININEC-type ground is selected.
...Use some other ground type for near field analysis.

Obviously, near-field analysis was not disabled by/in EZNEC for my
model definition.

How very odd, when this comes as a distinct contradiction with your
explicit:
The near-field analysis of EZNEC for radiation in the horizontal plane
at a point 1 km from a 1/4-wave monopole having two ohms in series
with a Mininec r-f ground, while radiating 1 kW over an earth
conductivity of 8 mS/m is shown as 72 mV/m.
where the question remains at:
where did you get
is shown as 72 mV/m.
from?
It is evident your field quote is NOT from this specific Mininec r-f
ground model of yours above.

As you admit you had near-field analysis available above (you still do
not explain how in the context of a mini-nec ground per your stated
model's characteristics), and you do not describe any radial treatment
(cogent elements of the BL&E paper "Ground Systems as a Factor in
Antenna Efficiency"), and you do describe a 1/4 radiator (not found in
BL&E experimental data), then your call for suggestions on how to fix
your model's failure in the context of BL&E becomes an obscure moving
target. My "suggestion" alters slightly with do it right or discard
it as trash. There aren't really many other alternatives.

Hopefully Roy Lewallen will weigh in, as he has time, to comment on
the methods and results of our two analyses -- although probably Roy
will need more details about your model construction than you have so
far been willing to provide.

More interesting would be his enquiry or explanation into how you
defeated the lock-out for a feature that is a poor method for near
field analysis. I find it more intriguing in how you embrace it in
spite of stated cautions to employ other methods. Yes, this novel
adaptation of Mininec r-f ground to near field solutions bears more
explanation from some source. I cannot imagine that explanation will
improve your model's performance to equal mine however. That is
already well evident.

As for more details, the BL&E paper "Ground Systems as a Factor in
Antenna Efficiency" is the totality of my sources. Those practiced in
the craft of modeling and proficient with its tools will find it
sufficiently informing if they hadn't already proceeded to a
successful implementation from my descriptions in this thread.

73's
Richard Clark, KB7QHC

Low-angle Elevation Gain of a 1/4-wave Vertical Monopole
 

On Nov 28, 12:51*pm, Richard Clark

where the question remains at: where did you get
...72 mV/m from?

It is evident your field quote is NOT from this specific Mininec r-f
ground model of yours above.

Can you not view the screen clip at the link I posted showing this?
Why do you keep asking?

All of the windows shown in my screen clip resulted from the NEC model
data appearing in the upper left window of that clip, and all windows
in the clip appeared on the screen at same time and were driven by
that data. Note the selection of a Real/MININEC ground in the EZNEC
window in the upper left corner, and the further selection of a
"medium ground" on the line below. One of the other windows there
shows the "near-field" value of 72 mV/m at 1 km for 1 kW of radiated
power for this model. Are you comprehending all that is shown in that
clip?

More interesting would be his enquiry or explanation into how you
defeated the lock-out for a feature that is a poor method for near
field analysis.

No defeat of such was necessary. EZNEC produced the data results for
my model exactly as shown in my screen clip, with no complaints or
subterfuge on my part.

RF

Low-angle Elevation Gain of a 1/4-wave Vertical Monopole
 

On Fri, 28 Nov 2008 12:07:05 -0800 (PST), Richard Fry
wrote:

On Nov 28, 12:51*pm, Richard Clark

where the question remains at: where did you get
...72 mV/m from?

It is evident your field quote is NOT from this specific Mininec r-f
ground model of yours above.

Can you not view the screen clip at the link I posted showing this?
Why do you keep asking?

Because in a commercial release, suitable to professional and
scholarly reporting, it is obviously locked out as an available option
- by design and documented as so. A screen shot does not describe
your actions. You need only explicitly state that when you selected
the mini-nec ground model, that you had the NF button available and
you selected it. If such is the case, it is a bug in Roy's demo -
caveat emptor. I don't do research with demo applications.

The long and short of it is that what your poor model reveals is a
departure from the data found in the BL&E paper "Ground Systems as a
Factor in Antenna Efficiency." You
1. do not have a construction of radials of any type;
2. do not have a radiator sized to their specification;
3. employ an engine (mini-nec) which is poorly suited to the task;
4. excite the model at a frequency not supported in data in BL&E;
5. fail to note the documented advisories about near field operation
below 3MHz when such analysis is available.

There is no point in asking for how to "fix it" when your model is
irreconcilably crippled. Using a demo version of EZNEC is not suited
to the task. You couldn't even use my model as it is constructed with
fine granularity that exceeds the capacity of EZNEC, and supported
only with EZNEC+. There are alternatives that are free, and unlimited
in their segment counts available which is necessary for a proper
analysis. Caveat emptor still prevails, and you get the quality of
support you pay for.

I would "suggest" given all the cautions, contrarian advisories
offered, and warnings direct from the tool's author, that their
cumulative effect would seem to doom you to disappointment if you
demand something better than several percent concurrence to the data
supplied in the BL&E paper "Ground Systems as a Factor in Antenna
Efficiency" when abstracted to other applications.

73's
Richard Clark, KB7QHC

Low-angle Elevation Gain of a 1/4-wave Vertical Monopole
 

On Nov 28, 3:24*pm, Richard Clark posted:

Can you not view the screen clip at the link I posted showing this?
Why do you keep asking?

Because in a commercial release, suitable to professional and
scholarly reporting, it is obviously locked out as an available option
- by design and documented as so.

A screen shot does not describe your actions. *You need only
explicitly state that when you selected the mini-nec ground model,
that you had the NF button available and you selected it. *

To humor you, then... I explicitly state that when I selected the Real/
MININEC ground model, I had the NF button available and that I
selected it. The result of that analysis is included in the screen
clip at the link I posted, and which you seem unable to comprehend.

Also please note that I have already described and documented my EZNEC
model and actions in far more detail than you have done for yours, so
far.

Note further that the Demo versions of EZNEC operate exactly the same
as the paid versions, except for the number of segments permitted in
the model -- which was not a factor in the model I constructed. I'm
sure that Roy or someone else will correct me if that statement is
provably wrong.

The long and short of it is that what your poor model reveals is a
departure from the data found in *the BL&E paper *"Ground Systems as a
Factor in Antenna Efficiency." *You

1. *do not have a construction of radials of any type;

Their effect was included as I described in an earlier post. I will
understand if this concept evades you.

2. *do not have a radiator sized to their specification;

A 1/4-wave monopole is a 1/4-wave monopole, regardless of the
operating frequency. The intrinsic radiation envelope for a given
radiated power actually launched by such a monopole (e.g., apart from
the effects of the propagation environment) is the same at all those
frequencies.

If not, the FCC would/could not have adopted the results of the BL&E
experiments at 3 MHz as applicable to the entire MW AM broadcast band
(which they did).

3. *employ an engine (mini-nec) which is poorly suited to the task;

A MININEC ground itself is not an engine. It is a only a condition
used by the NEC engine.

4. *excite the model at a frequency not supported in data in BL&E;

See my response to your 2 above. In reality, surface-wave ground
losses in the MW BC band are less than at the 3 MHz freq used in the
BL&E studies, so the applicability of their findings is even more
relevant to BC operations.

5. *fail to note the documented advisories about near field operation
below 3MHz when such analysis is available.

No such advisory was presented by/in EZNEC during the process of
generating and analyzing my model.

I suggest you cool it for a while, and wait to see what Roy Lewallen
might post about all of this.

RF

Low-angle Elevation Gain of a 1/4-wave Vertical Monopole
 

It's possible to run a near field analysis using MININEC type ground
with some v. 4.0 and all v. 3.0 and earlier versions of EZNEC. However,
the results will be wrong. The problem with using near field analysis
and MININEC type ground was discovered while v. 4.0.27 was current, and
the restriction preventing that combination was introduced at v. 4.0.28
in August 2006. So only v. 4.0.28 and later programs have this
restriction. Please see the last paragraph of this posting for remedies.

In EZNEC v. 4.0.28 and later, the NF Tab button is greyed out whenever a
MININEC-type ground is specified. If it's clicked, you'll see a message
that near field analysis is disabled when MININEC-type ground is
specified. If you click Help in the message window, it'll open the
manual topic which discusses real ground types. There, you'll find:

---------------

Near field analysis is disabled when MININEC-type ground is selected.

Tests have shown that, because of the fundamental way NEC does
calculations, near field analysis with MININEC-type ground can produce
significantly erroneous results, particularly in the vicinity of a wire
which is connected to ground. This is really a contrived situation
anyway, because the only way to achieve a ground connection for a real
antenna comparable to the MININEC-type ground model is to install a
radial system. This will alter the ground conductivity and local fields,
so the MININEC-type ground model isn't really representative of
conditions near a grounded wire in any case. Use some other ground type
for near field analysis.

---------------

If the conclusion that EZNEC near field results differ from the FCC
ground wave predictions is based on a near field analysis with
MININEC-type ground, I'm not surprised at the disagreement. The analysis
should be redone with a large number of radials just above the ground,
and High Accuracy ground used instead of MININEC-type ground.

Two reminders:

1. As explained in the EZNEC manual, "near field" analysis isn't
restricted to the near field. It's actually "total field" -- including
ground wave -- and is accurate at any reasonable distance. The "near
field" nomenclature is carried over from NEC.
2. The EZNEC ground model is flat and infinite in extent. So the
predicted direct line field begins deviating from actual field values
where the curvature of the Earth becomes a significant factor.

Anyone using EZNEC v. 3.0 and earlier should avoid using the combination
of near field analysis and MININEC-type ground. Anyone using v. 4.0
should update his program to the last revision of that version, 4.0.39.
You can find instructions on updating in the manual, Support/Updates
(Maintenance Releases). To determine which revision you have, click Help
in the main program window, then About EZNEC. I strongly recommend that
v. 5.0 users periodically check for updates.

Roy Lewallen, W7EL

Low-angle Elevation Gain of a 1/4-wave Vertical Monopole
 

On Fri, 28 Nov 2008 15:39:35 -0800 (PST), Richard Fry
wrote:

wait to see what Roy Lewallen might post about all of this.

Are you going to ask for a refund?

73's
Richard Clark, KB7QHC

Low-angle Elevation Gain of a 1/4-wave Vertical Monopole
 

Richard Fry wrote:
. . .
Note further that the Demo versions of EZNEC operate exactly the same
as the paid versions, except for the number of segments permitted in
the model -- which was not a factor in the model I constructed. I'm
sure that Roy or someone else will correct me if that statement is
provably wrong.
. . .

You are correct. The demo is exactly the same as the standard EZNEC
program except for the segment limitation. But I recommend using the
current demo program rather than an older version or revision. Demo
programs can be updated at any time by downloading and installing the
current demo from http://eznec.com/demoinfo.htm. The old program can be
uninstalled first if desired; otherwise the new one will overwrite the
old one. This process won't harm any saved description files.

Roy Lewallen, W7EL