OK, I apparently drifted off the beaten path plus I seem to be
experiencing some serious brain fade.

What I was doing was preparing a short presentation for new hams on
the subject of vertical antennas. I was using EZNEC to produce some
antenna pattern graphics. It was then that I noticed that when I
overlayed the pattern from a vertical half wavelength dipole with that
of a horizontal half wave dipole at the same center height over real
ground that the pattern from the vertical was completely enclosed by
the horizontal dipole pattern, at least broadside to the horizontal
dipole that is. The vertical dipole pattern definitely showed a lower
angle of peak radiation but no greater gain a low angles than the
horizontal dipole.

At first, seeing the vertical dipole gain the same as the horizontal
dipole, even at low elevation angles, was a little confusing but I had
just scanned a bit of text on vertical antenna operation including
calculation for reflected waves and stuff like the pseudo Brewster
angle.

But then... I remembered talking to a couple guys in Germany on 75
meters the previous evening. From my location here in Missouri, I was
hearing their signals on my 75 meter inverted L much stronger at 10 to
20 over S9 than on my dipole at S4 to S5. They noted the same
difference in performance between the two antennas. As both the
Dipole height and the top of the inverted L were at 50 feet, I thought
this was a reasonable comparison. Also, the dipole is in the clear,
resonant, and has been performing as well or better than other
horizontal dipoles used by other hams in this area.

Furthermore, my experience switching between horizontal and vertical
antennas on 75 meters matched that of other guys with both. I was
starting to wonder why the mismatch between the theory I was familiar
with and my experiences.

Jumping back in to the text books and spending some time 'googling'
for more info I found nothing to conflict with the material I had
previously covered. That was disconcerting. About the only glimmer
of a solution to the question popped up when I looked at papers on
ground or surface wave propagation. There were some vague comments
about diffraction that seemed to indicate one of the loss factors
involved with ground wave propagation is that some of the signal does
not get diffracted low enough to keep in from being 'lost' to sky wave
radiation.

As I continued chasing that thought, I found that discussions of sky
wave propagation ignored ground wave and discussions of ground wave
propagation considered sky wave as lost RF.

Now, after all that windup, what am I missing? I acknowledge ahead of
time that I may be a dummy so don't bother explaining that to me. Why
do reasonable size vertical antennas with proper radial systems under
them outperform horizontal dipoles for DX operation for typical ham
antenna support structure heights of 50 feet or so?

The interesting question then: Is the improved performance of
vertical antennas over horizontal dipoles on 75 meters at DX distances
due to a combination of direct radiation plus radiation from the
ground in the area of strong ground wave strength out hundreds of
meters? Is the ground wave leakage providing additional low signal
strength in both transmit and receive?

Gary - N0GW

On Wed, 13 Feb 2008 20:58:31 -0800 (PST), N0GW
wrote:

It was then that I noticed that when I
overlayed the pattern from a vertical half wavelength dipole with that
of a horizontal half wave dipole at the same center height over real
ground that the pattern from the vertical was completely enclosed by
the horizontal dipole pattern, at least broadside to the horizontal
dipole that is. The vertical dipole pattern definitely showed a lower
angle of peak radiation but no greater gain a low angles than the
horizontal dipole.

Hi Gary,

You have so much left unsaid, that it is shooting in the dark.
However, proceeding with that risk in mind....

A vertical dipole described above is not the vertical antenna that you
describe following:
The interesting question then: Is the improved performance of
vertical antennas over horizontal dipoles on 75 meters at DX distances
due to a combination of direct radiation plus radiation from the
ground in the area of strong ground wave strength out hundreds of
meters? Is the ground wave leakage providing additional low signal
strength in both transmit and receive?

Better? You are relying too heavily on anecdotal reports.

For one, I seriously doubt you compared a 75M vertical dipole to a 75M
horizontal dipole in your lecture - no one in your audience would have
the financial clout to go there I suspect. That vertical dipole tip
would have to be hoisted quite a distance to see that the bottom tip
wasn't buried in the earth.

The next problem is height (again) and how it contributes to (or
subtracts from) gain as that varies. There is no "similar" comparison
between the two. You could model and present variations on horizontal
dipole elevation alone for two hours, much less both of them.

Rule 1 of presentations: Don't give them off the cuff unless you are
prepared to follow the surprises.

Rule 2: If you are willing to follow the surprises; then you aren't
really giving a presentation.

73's
Richard Clark, KB7QHC

N0GW wrote:
OK, I apparently drifted off the beaten path plus I seem to be
experiencing some serious brain fade.

What I was doing was preparing a short presentation for new hams on
the subject of vertical antennas. I was using EZNEC to produce some
antenna pattern graphics. It was then that I noticed that when I
overlayed the pattern from a vertical half wavelength dipole with that
of a horizontal half wave dipole at the same center height over real
ground that the pattern from the vertical was completely enclosed by
the horizontal dipole pattern, at least broadside to the horizontal
dipole that is. The vertical dipole pattern definitely showed a lower
angle of peak radiation but no greater gain a low angles than the
horizontal dipole.

That's because the energy radiated at lower angles with vertical
polarization is actually absorbed and dissipated in the ground, while
very little of the horizontally polarized antenna energy is.

At first, seeing the vertical dipole gain the same as the horizontal
dipole, even at low elevation angles, was a little confusing but I had
just scanned a bit of text on vertical antenna operation including
calculation for reflected waves and stuff like the pseudo Brewster
angle.

But then... I remembered talking to a couple guys in Germany on 75
meters the previous evening. From my location here in Missouri, I was
hearing their signals on my 75 meter inverted L much stronger at 10 to
20 over S9 than on my dipole at S4 to S5. They noted the same
difference in performance between the two antennas. As both the
Dipole height and the top of the inverted L were at 50 feet, I thought
this was a reasonable comparison. Also, the dipole is in the clear,
resonant, and has been performing as well or better than other
horizontal dipoles used by other hams in this area.

Furthermore, my experience switching between horizontal and vertical
antennas on 75 meters matched that of other guys with both. I was
starting to wonder why the mismatch between the theory I was familiar
with and my experiences.

Tom Rauch, W8JI, has the capability to run some pretty good comparisons
under near-textbook conditions, and he's consistently observed the same
thing on 160 and 80.

Jumping back in to the text books and spending some time 'googling'
for more info I found nothing to conflict with the material I had
previously covered. That was disconcerting. About the only glimmer
of a solution to the question popped up when I looked at papers on
ground or surface wave propagation. There were some vague comments
about diffraction that seemed to indicate one of the loss factors
involved with ground wave propagation is that some of the signal does
not get diffracted low enough to keep in from being 'lost' to sky wave
radiation.

As I continued chasing that thought, I found that discussions of sky
wave propagation ignored ground wave and discussions of ground wave
propagation considered sky wave as lost RF.

Now, after all that windup, what am I missing? I acknowledge ahead of
time that I may be a dummy so don't bother explaining that to me. Why
do reasonable size vertical antennas with proper radial systems under
them outperform horizontal dipoles for DX operation for typical ham
antenna support structure heights of 50 feet or so?

The interesting question then: Is the improved performance of
vertical antennas over horizontal dipoles on 75 meters at DX distances
due to a combination of direct radiation plus radiation from the
ground in the area of strong ground wave strength out hundreds of
meters? Is the ground wave leakage providing additional low signal
strength in both transmit and receive?

The short answer is that I don't think anyone really knows. I'm
convinced that the program accurately calculates the field from the
antenna and environment specified by the model. But there are some
pretty significant ways in which the model doesn't represent reality.
EZNEC uses the NEC ground model which is highly simplified - its ground
is perfectly flat, homogeneous to an infinite depth, and infinite in
extent. Real ground is curved and stratified with many layers of
sometimes highly differing conductivity and permittivity. Besides the
deficiency of the ground models, there might be some interesting
phenomena like ground wave energy following the ground for a while, then
launching some distance from the antenna. This wouldn't be modeled
properly by EZNEC or NEC. And although polarization is rotated during
ionospheric propagation, maybe there's some inherent advantage to
launching a vertically polarized signal. EZNEC and NEC make no attempt
at modeling propagation. Anecdotal evidence seems to find more of a
disparity between model results and observations at low frequencies (80
meters and below) than higher frequencies. Whether this is due to the
greater ground skin depth at lower frequencies, different propagation
effects, or maybe just the vagaries of anecdotal reporting, is something
I don't think anyone knows.

Roy Lewallen, W7EL

Roy Lewallen wrote:
... there might be some interesting
phenomena like ground wave energy following the ground for a while, then
launching some distance from the antenna. This wouldn't be modeled
properly by EZNEC or NEC.

Could that possibly be the result of the curvature
of the earth?
--
73, Cecil http://www.w5dxp.com

On Feb 14, 12:03 am, Richard Clark wrote:

You have so much left unsaid, that it is shooting in the dark.
However, proceeding with that risk in mind....

A vertical dipole described above is not the vertical antenna that you
describe following:

Better? You are relying too heavily on anecdotal reports.

The next problem is height (again) and how it contributes to (or
subtracts from) gain as that varies. There is no "similar" comparison
between the two. You could model and present variations on horizontal
dipole elevation alone for two hours, much less both of them.

Rule 1 of presentations: Don't give them off the cuff unless you are
prepared to follow the surprises.

Rule 2: If you are willing to follow the surprises; then you aren't
really giving a presentation.

73's
Richard Clark, KB7QHC

Richard, thanks for the comments. Yep, I thought of the thing about
the model versus the inverted L mentioned after I had already sent the
message. What I should have mentioned is that the EZNEC pattern for
the inverted L showed lower gain than the vertical dipole.

As for the anecdotal evidence thing: It's my observation. My
756ProIII S meter may not be a calibrated piece of test equipment but
the deflection of the needle was much higher while listening with the
inverted L. While I can't give an quantitative number to the
difference in strength, I can say qualitatively that the Inverted L
provided a much stronger and clearer signal.

As for the presentation, that is why I'm here asking the question. No
point in putting out info if it is going to be bogus. I saw a
discrepancy between my experience and the text books. I'm just trying
to resolve that.

Thanks again.

Gary - N0GW

On Thu, 14 Feb 2008 06:10:23 -0800 (PST), N0GW
wrote:

As for the presentation, that is why I'm here asking the question. No
point in putting out info if it is going to be bogus. I saw a
discrepancy between my experience and the text books. I'm just trying
to resolve that.

Hi Gary,

Experience is often the most confounding experience you will ever
experience.

After all, does experience explain the angle at which you
receive/transmit that portion of signal in a circuit (the jargon for
connection between you and that distant operator)? NVIS can hammer a
vertical, if that is what you want; even if you forget to lift the
horizontal into the air. So a horizontal dipole on the ground is the
best antenna compared to the best vertical? Not when you shift bands
and target a DX station.

Does experience explain the difference in (at what would be a strain
to justify) "a vertical at the same height as a horizontal dipole?" To
fill in that last parenthetical: What makes a vertical dipole at an
EQUAL height to a horizontal dipole? The equal high feed points? The
equal highest point of metal? The equal average height of both?
Choose any one of three and the other two could have better
performance over the other - and still someone in the audience could
cry nothing can be said to be EQUAL.

Does the experience at 160M with a ground mounted vertical translate
into the same experience at 10M? Experience in the 'burbs with trees,
homes, sheds, cars, playsets in the vicinity would suggest no. An
antenna 16 times taller can see over those same things which are
barely dimples to the field.

A head-to-head comparison will quickly resolve; but as this is an
amateur society with limited antenna options and a multitude of band
choices, experience will often roller-coaster between disappointment
and elation - and as so often proven in threads of amazing inventions
here, those inventors demand classical text books should be discarded
as being obviously counter to "experience."

The emerging new invention of an 160M band antenna the size of two
shoe-boxes should show how plastic and flexible experience is such
that it can stretch to fit into a suit 300 times it size.

73's
Richard Clark, KB7QHC

On Feb 14, 12:13 am, Roy Lewallen wrote:
snip

The short answer is that I don't think anyone really knows. I'm
convinced that the program accurately calculates the field from the
antenna and environment specified by the model. But there are some
pretty significant ways in which the model doesn't represent reality.
EZNEC uses the NEC ground model which is highly simplified - its ground
is perfectly flat, homogeneous to an infinite depth, and infinite in
extent. Real ground is curved and stratified with many layers of
sometimes highly differing conductivity and permittivity. Besides the
deficiency of the ground models, there might be some interesting
phenomena like ground wave energy following the ground for a while, then
launching some distance from the antenna. This wouldn't be modeled
properly by EZNEC or NEC. And although polarization is rotated during
ionospheric propagation, maybe there's some inherent advantage to
launching a vertically polarized signal. EZNEC and NEC make no attempt
at modeling propagation. Anecdotal evidence seems to find more of a
disparity between model results and observations at low frequencies (80
meters and below) than higher frequencies. Whether this is due to the
greater ground skin depth at lower frequencies, different propagation
effects, or maybe just the vagaries of anecdotal reporting, is something
I don't think anyone knows.

Roy Lewallen, W7EL

Thanks Roy, but darn, I was hoping that was not the answer. I was
hoping this was a subject someone had worked through definitively. Oh
well. What counts is how well an antenna works, not what calculations
show.

At no point did I think that EZNEC and NEC2 were busted. The output I
saw matched expectations arrived at from digging through text books
and scientific papers. I was eventually looking for a clue as to what
the NEC2 algorithms might be missing. I found the "leaky ground wave"
thing for lower frequencies an intriguing idea. I expect that above
about 10 MHz, where ground wave propagation becomes a fairly minor
consideration, NEC2 should provide a fairly accurate prediction of
vertical antenna performance.

Gary - N0GW

AI4QJ wrote:

I suspect that the EZNEC program is not designed for taking into account
such "rare" phenomena as "ground wave propagation". So much for EZNEC
analysis at 75m.


My own experiments with vertical vs dipole led me to the conclusion
that they both work better than the other, and they both work worse than
each other.

I based my analysis on signal strength using a db pad to match for the
weakest signal vs the strongest one. You can't do this one with just the
S-Meter, they aren't very accurate.

Sometimes the vertical "worked" better, and sometimes the horizontal
did. And while a generalization could be made for distance, therefore
"take off angle" between the two antennas, the reception could change
in the middle of a QSO, favoring one other the other.


Comparing one antenna against another is quite difficult - at least to
say which one "works" better.

And I'm curious - where is the propagation function in EZNEC?


- 73 de Mike N3LI -

On Feb 15, 12:52*pm, Michael Coslo wrote:
AI4QJwrote:
I suspect that the EZNEC program is not designed for taking into account
such "rare" phenomena as "ground wave propagation". So much for EZNEC
analysis at 75m.

* * * * My own experiments with vertical vs dipole led me to the conclusion
that they both work better than the other, and they both work worse than
each other.

I based my analysis on signal strength using a db pad to match for the
weakest signal vs the strongest one. You can't do this one with just the
S-Meter, they aren't very accurate.

* * * * Sometimes the vertical "worked" better, and sometimes the horizontal
did. And while a generalization could be made for distance, therefore
"take off angle" *between the two antennas, the reception could change
in the middle of a QSO, favoring one other the other.

Comparing one antenna against another is quite difficult - at least to
say which one "works" better.

* * * * And I'm curious - where is the propagation function in EZNEC?

* * * * *- 73 de Mike N3LI -

There is none, of course. You would have to construct the lobes on an
asimuth chart but this is only useful for take-off angle and skywave
propagation. EZNEC information tells you nothing about ground wave
propagation.

On Fri, 15 Feb 2008 12:37:55 -0800 (PST), wrote:

AI4QJwrote:
I suspect that the EZNEC program is not designed for taking into account
such "rare" phenomena as "ground wave propagation". So much for EZNEC
analysis at 75m.
....
EZNEC information tells you nothing about ground wave
propagation.

Two things wrong with this:
1. EZNEC does provide information about the radiation characteristics
along ground at any distance on an infinite, flat plane and at any
elevation above it;
2. EZNEC is not a propagation modeler as its users are well aware;
3. EZNEC models the 100M work of Brown, Lewis, & Epstein quite
closely. There is nothing in the body of RF literature to suggest
that the nature of radiation shifts suddenly in 7/8ths of a megahertz.

73's
Richard Clark, KB7QHC