John Popelish wrote:
Cecil Moore wrote:

John Popelish wrote:

Cecil Moore wrote:

I don't demand agreement, John, just resolution.


Resolution in who's mind?


In mine, of course. I am obsessive-compulsive that way.
Sorry about that - it's probably a character flaw.


Then you also probably believe that a character flaw is an absolute, as
are and evil.

I dropped a word during editing. That should have read:

Then you also probably believe that a character flaw is an absolute,
as are good and evil.

Tom Donaly wrote:
Cecil Moore wrote:
Tom Donaly wrote:
Besides, you said, yourself, that Cecil
is always right.

False. Reg didn't say that.

He said it under his breath as he was writing it to this
newsgroup.

If Reg actually believed that, he wouldn't argue
with me so much. :-)
--
73, Cecil http://www.qsl.net/w5dxp

John Popelish wrote:
Cecil Moore wrote:
I am obsessive-compulsive that way.
Sorry about that - it's probably a character flaw.

Then you also probably believe that a character flaw is an absolute, as
are (good) and evil.

"If it's not a 'one' or a 'zero', it's broke." :-)
--
73, Cecil http://www.qsl.net/w5dxp

Ron wrote:
Ok I am getting confused. You are saying that a groundplane will not
work as good a a ground mounted vertical ? At what angle are you
talking about? Are you more interested in working 500 miles or 6,000
miles?

Ron

Nope. I think the elevated ground plane is superior to the
ground mount as long as it's high enough in the air to avoid
excess ground loss. As far as long haul, there may not be
too large a difference if each system is equal as far as ground
loss. IE: a ground mount with 120 radials, and a GP at 1/2 wave
high with 4 radials should show about the same efficiency. So
for long haul dx, they should be fairly close in theory. But...
You have a better ground/space wave with the elevated antenna.
This can come in handy when talking 50-100 miles away when
the band doesn't support NVIS with a dipole, etc..
When you run the elevated antenna, you must always think of
height in terms of wavelength, not feet or meters. A 2 meter GP
can be fairly low, and still very efficient. But not a low band GP.
A half wave is a different height on each band. Being I recommend
a minimum of 1/4 wave height when using only 4 radials, that
can be pretty high on a lower frequency. On 40m, I ran one at
36 ft at the base of the radiator. Thats just over 1/4 wave up.
If I ran the same antenna on 80m, I would have to mount it at
72 ft to have the same efficiency. About 145 ft on 160m.
Soooo...If you can't go that high, you must increase the number
of radials to lower the ground losses to a equal number.
If you have a ground mount with 120 radials, you need about 60 radials
if the antenna is at 1/8 wave. About 8-12 radials if the antenna is at
1/4 wave. About 3-4 radials if the antenna is at 1/2 wave. All these
have the same appx ground losses. So you can see, if you run a 80m
ground plane at 15 ft, the ground losses will be high unless you use
a whole lot of radials. So in that case, it's really more practical to
use the ground mount unless you don't mind all that wire in the air.
But equal loss ground mount vs ground plane? I'd take the ground
plane anyday... I ran one on 40m and it kicked serious butt on
long haul dx. And yes, I use the verticals on the low bands for
mostly long haul. I use dipoles, etc for NVIS.
MK

One of the earlier postings suggested that the quarterwave vertical antenna
with radials was elementary and easy to understand. I have never found this
antenna easy to understand.

RF experts on this newsgroup cannot agree on whether i) the radials reflect
the wave or ii) the field from the radials cancels out. The standard
academic books show that the principle behind the vertical ground plane
antenna is that the vertical radiating element emits the wave, and is
reflected by the ground plane.

You can view a conductor as having current pushed through it by a RF source,
or the current can be induced in the conductor by the wave. This is a
boundary condition in Maxwell's equations, referred to in theory of
transmission lines and guided waves.

You can view the radials as reflecting the wave and having current induced
in them, or they can have current pushed through them by the RF source. This
is probably the same thing, due to the arrangement of all antenna parts
forming the antenna impedance. In image theory, the impedance comes from
both the self impedance and the mutual impedance.

It appears that a single counterpoise wire is connected to the RF ground
side to provide a conductor for that side and be a form of dipole. If a
proper RF ground is not provided, the result may be RF in the shack e.g. the
RF tries to return via mains wiring. Does connecting several wires make the
RF ground side less live i.e. occupying a larger area to be more of a
reflector and thus dissipative? If a RF ground is live, it can be dangerous
to touch it. Do you increase the area of RF ground to make it less dangerous
to touch e.g. radials under a carpet when relatives and pets are about?

The theory behind the quarterwave vertical is the monopole above a ground
plane, where the ground plane reflects the wave emitted by the vertical.
The monopole is explained using image theory. In practice, the ground plane
is
replaced by radials. Do the radials reflect the wave then?

The reflecting element on a Yagi manages to reflect most of the wave. The
reflecting element on a Yagi is a parasitic element that has an impedance
to cause the wave emitted by the driven element to flow in a particular
direction. A Yagi normally has only one reflector. Although the reflector
is in the near field of the Yagi, can a comparison be made with the radials
of
a quarterwave vertical antenna? The reflector on a Yagi is usually a thin
tube with lots of air (gap) around it. Even though it occupies a small
area, it still manages to reflect most of the wave. Yagi has a Front to
Back
ratio in dB.

Radials can be tuned. Some antennas have loading coils in the radials.


Antenna theory is often about wires and metallic items reflecting waves,
and the phase of the reflected wave. The phase of the reflected wave can be
constructive or destructive, affecting the impedance of the antenna. If an
antenna is mounted too close to the ground, the reflected wave cancels out
the emitted wave.

Because a ground plane reflects the wave, the impedance of an antenna can
vary with height.

Parastic elements on a Yagi have a mutual impedance to each other. Would
you regard the radials on a quarterwave vertical as having a mutual
impedance?

The radials increase the conductivity below the radiating element,
decreasing ground losses. The radials are regarded as a finite or imperfect
ground plane.

References:
"Antenna Theory and Design" by Warren Stutzman and Gary Thiele. pages 66 to
68. Practical monopole with radial wires to simulate a ground plane.
"Antenna Engineering Handbook" by Richard C. Johnson. Radials suppress
currents from flowing on outside of coax. p 28. If the ground is imperfect,
the perfect reflected image is mutiplied by a complex ground reflection
coefficient. The ground has a mutual impedance.
"Antenna Theory" by Professor Constantine Balanis. Second Edition p 165. A
ground plane formed by a perfect conductor completely reflects the wave. If
the ground is finite i.e. not as conductive, it still reflects the wave but
not as well. The conductivity determines the quality of the reflection.

Cecil Moore wrote:
plane of the radials.

Just ran that test. There was 0.02 dB difference at +45 and -45.

Run the test again more carefully. You are looking at something wrong.

Perhaps you didn't look at the entire azimuth plot at 45 degrees
elevation.

There is a large skew with a 1/4 wl vertical over two 1/4 wl radials,
and it gets worse at higher elevation numbers.

wrote:
There is a large skew with a 1/4 wl vertical over two 1/4 wl radials,
and it gets worse at higher elevation numbers.

Who said anything about two radials? I am reporting
the standard model with four radials. I was away
from my computer for four days over the holidays
and may have missed the two radial discussion, if
there was one.

The radial radiation cancellation that I earlier
described was based on four radials, certainly
not on two.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
wrote:
There is a large skew with a 1/4 wl vertical over two 1/4 wl radials,
and it gets worse at higher elevation numbers.

Who said anything about two radials?

Actually YOU did. Several times as a matter of fact.

I am reporting
the standard model with four radials. I was away
from my computer for four days over the holidays
and may have missed the two radial discussion, if
there was one.

The radial radiation cancellation that I earlier
described was based on four radials, certainly
not on two.
--
73, Cecil http://www.qsl.net/w5dxp

Here is what you said on this very thread:

Cecil Moore wrote:
Tom Donaly wrote:
If you can bring yourself to think in terms of
current directions and far field superposition of waves, this
behavior shouldn't be that hard to understand.

It's pretty easy to understand. Any two radials,
180 degrees apart and high enough, should theoretically
cancel each other's radiation in the far field.
--
73, Cecil http://www.qsl.net/w5dxp

Maybe reading one of your own posts will jog your memory a bit. In it
we see you VERY CLEARLY stated two radials would cancel each other's
radiation.

73 Tom

On Tue, 11 Jul 2006 12:36:18 -0400, John Popelish
wrote:

The center line I am referring to is the mirror line of the ground
plane or radial group that allows a monopole to have a field pattern
(both E and H) above that mirror line, that would exist there, if the
antenna was a symmetrical dipole. Without the mirror effect, the
field pattern of the monopole depends on the path the feed line takes
away from the monopole, and any other conductive objects nearby.

Hi John,

This is still rather obscure. You are not talking about a line, but
yet another plane. World of difference there, but I won't dispute
semantics further.

Simply raise that monopole, complete with radial plane and the center
line (as you call it), ABOVE the ground plane. I've already analyzed
this elsewhere in conventional jargon, but here it seems Photons offer
a different conclusion. Unfortunately you aren't prepared to pursue
this as you admit later.

The conventional analysis is perfectly capable of dealing with feed
lines or by avoiding them altogether. One can certainly conspire to
fail and corrupt the analysis, so avoiding distractions and placing
the source in the model, at the feedpoint, removes a lot of
uncertainty.

Since I am talking about field patterns, it seemed natural to switch
from total radiated watts to field intensities and the photons that
field emits and where those photons head.

Photons (as any radiation in this case) are incoherent and radiate in
all directions.

While amateurs may ultimately be interested in radiating power in
particular directions, we are discussing the physics of the radiation
process, and photonics is one way to think about that process.

I am perfectly content and competent to that goal.

The ultimate radial pattern is a solid disk. Once you understand what
that does to the field pattern, you can start toward a radial wire
layer, and see how, in important ways, like the ability to carry
radial current, it resembles a disk. Then, you can explore how
reducing the number of radials alters the approximation.

I don't see a photon in this at all.

You were going to tie this all together weren't you?

Probably not, since I am working through the process in my own mind.
I am not the teacher so much as a student trying to learn something
useful. I hope my posts generate more useful discussion from others
than I have gotten from you, so far.

I have, with neutral objectivity, posed issues of diffraction. For
one, the quarterwave antenna, in close proximity to a quarterwave
mirror (those radials), does not present the characteristics of a
point source that might render attractive solutions. Further, even a
point source ray striking a quarterwave mirror suffers considerably.

The long and short of it is that Photons make for an interesting
discussion with regards to antennas. Unfortunately, and as you
obliquely observe about me writing for myself, it seems I'm the only
one willing to carry the topic.

73's
Richard Clark, KB7QHC

wrote:

Maybe reading one of your own posts will jog your memory a bit. In it
we see you VERY CLEARLY stated two radials would cancel each other's
radiation.

73 Tom


Won't matter, he'll have an explanation for it, and it will be anyone's
fault but his.

tom
K0TAR