horizontally polarized antenna over ground plane
 

Greetings to all the antenna experts here!

I want to create horizontally polarized antenna, low profile, located above
large ground plane. And I need it to be omnidirectional (sort of) and have
sufficient gain in horizontal plane.

My frequency of interest is 900 MHz. The ground plane is a roof of a car.

I tried loops, from 50 to 300 mm diameter, radiation goes up if I mount it
above the ground plane.

Any ideas?

Thank you,

Andrey

"Bill Turner" wrote in message
...
On Sat, 4 Sep 2004 14:57:09 -0700, "Andrey"
wrote:

Greetings to all the antenna experts here!
I want to create horizontally polarized antenna, low profile, located
above
large ground plane. And I need it to be omnidirectional (sort of) and
have
sufficient gain in horizontal plane.
My frequency of interest is 900 MHz. The ground plane is a roof of a car.
I tried loops, from 50 to 300 mm diameter, radiation goes up if I mount
it
above the ground plane.
Any ideas?
Thank you,
Andrey

__________________________________________________ _______

FWIW, horizontal polarization at 900 MHz won't get you far. Vertical is
preferred because horizontal is rapidly absorbed by ground loss. On the
other hand, if you don't *want* to get very far, use a vertical and just
reduce power.
This will be sad news to all the V/U weak signal ops who have consistantly
covered long distances using horizontal polarity.

Dale W4OP

To Bill Turner,

my tests showed no difference between Horizontal and Vertical propagation.
Vertical is quite busy here, lots of interference. Horizontal, on the other
hand plays much better.

My question was antenna design, not the propagation issues. Thanks for
trying though.

Andrey



"Dale Parfitt" wrote in message
news:mIs_c.2344$vI2.712@trnddc02...

"Bill Turner" wrote in message
...
On Sat, 4 Sep 2004 14:57:09 -0700, "Andrey"
wrote:

Greetings to all the antenna experts here!
I want to create horizontally polarized antenna, low profile, located
above
large ground plane. And I need it to be omnidirectional (sort of) and
have
sufficient gain in horizontal plane.
My frequency of interest is 900 MHz. The ground plane is a roof of a
car.
I tried loops, from 50 to 300 mm diameter, radiation goes up if I mount
it
above the ground plane.
Any ideas?
Thank you,
Andrey

__________________________________________________ _______

FWIW, horizontal polarization at 900 MHz won't get you far. Vertical is
preferred because horizontal is rapidly absorbed by ground loss. On the
other hand, if you don't *want* to get very far, use a vertical and just
reduce power.
This will be sad news to all the V/U weak signal ops who have
consistantly
covered long distances using horizontal polarity.

Dale W4OP

Andrey wrote:
Greetings to all the antenna experts here!

I want to create horizontally polarized antenna, low profile, located above
large ground plane. And I need it to be omnidirectional (sort of) and have
sufficient gain in horizontal plane.

My frequency of interest is 900 MHz. The ground plane is a roof of a car.

I tried loops, from 50 to 300 mm diameter, radiation goes up if I mount it
above the ground plane.

Any ideas?

Thank you,

Andrey


Good Morning Andrey,

What you are proposing is not an easy task any horizontal antenna placed
close to a good ground plain is going to have most of it's signal at
90 degrees. ( Straight up) Until the antenna is at least 1/2 wave above
the ground plan. at that point it will start to show radiation to the
horizon. EZNEC shows max gain at 30 degrees to the horizon for a 1/2
wave horizontal dipole mounted 1/2 wave above perfect ground and the
pattern looks somewhat like a peanut shape. if you move the antenna up
to 1 fullwave length above the ground plain then the patern does not
change much but the elevation angle dose you then get a good lobe at 15
degrees and another at 45 degrees. hope this is of some help.
Dave kc1di

Thank you Dave,

for sharing with me results of your simulation. I got similar results. The
thing that works is slit pipe (Alford's slot, see
http://www.eta.chalmers.se/~pgp/alfo...lford_eng.html for example)

Pipe works over ground plane as well (not as well, beam gets lifted, stll
there is enough energy looking on the horizon). It is such a cumbersome
thing though - looks funny on car's roof. Not of ractical use.

And I still can not find anything else that does it.


Regards,

Andrey Gleener


"KC1DI" wrote in message
...
Andrey wrote:
Greetings to all the antenna experts here!

I want to create horizontally polarized antenna, low profile, located
above
large ground plane. And I need it to be omnidirectional (sort of) and
have
sufficient gain in horizontal plane.

My frequency of interest is 900 MHz. The ground plane is a roof of a
car.

I tried loops, from 50 to 300 mm diameter, radiation goes up if I mount
it
above the ground plane.

Any ideas?

Thank you,

Andrey


Good Morning Andrey,

What you are proposing is not an easy task any horizontal antenna placed
close to a good ground plain is going to have most of it's signal at
90 degrees. ( Straight up) Until the antenna is at least 1/2 wave above
the ground plan. at that point it will start to show radiation to the
horizon. EZNEC shows max gain at 30 degrees to the horizon for a 1/2
wave horizontal dipole mounted 1/2 wave above perfect ground and the
pattern looks somewhat like a peanut shape. if you move the antenna up
to 1 fullwave length above the ground plain then the patern does not
change much but the elevation angle dose you then get a good lobe at 15
degrees and another at 45 degrees. hope this is of some help.
Dave kc1di

"Bill Turner" wrote in message
...
On Sun, 05 Sep 2004 00:02:26 GMT, "Dale Parfitt"
wrote:

This will be sad news to all the V/U weak signal ops who have
consistantly
covered long distances using horizontal polarity.

__________________________________________________ _______

This fellow was planning to put his antenna on the roof of a car.
Presumably he is *not* DXing.

I was therefore speaking of groundwave coverage, not any kind of skip,
and what I stated holds true; for local groundwave, vertical is best.

DXers, on the other hand, use horizontal precisely because the local
groundwave coverage is poor, thereby reducing local QRM but having
little or no effect on skip signals.

--
Bill, W6WRT
QSLs via LoTW


I wasn't talking about skip either- the majority of V/U weak signal work is
extended ground wave via perhaps enhanced tropo.

1.Horizontal polarity can take advantage of ground gain reflection that
vertical polarity cannot.

2. In addition, at 900 MHz where a wavelength is just over a foot, even
mounting the antenna at 12" would place the first lobe at 15 degrees,
assuming the car roof completely determines this- and I doubt that it has
much of an effect on far field take off angle.

Dale W4OP

I sense there's still a failure to communicate.

If Dale means by "V/U" VHF and UHF, ground wave isn't a viable means of
propagation anyway. The attenuation of ground waves increases with
frequency, to the point that they're virtually useless at VHF and above.
So at those frequencies, I'd think the polarization choice for short
range communication would be based on how it affects attenuation,
multipath, and QRM. Given those criteria, horizontal might well have an
advantage for short range communication, in some locations at least. And
it's long been favored for long range VHF/UHF communication.

Roy Lewallen, W7EL

Bill Turner wrote:
On Sun, 05 Sep 2004 00:02:26 GMT, "Dale Parfitt"
wrote:


This will be sad news to all the V/U weak signal ops who have consistantly
covered long distances using horizontal polarity.


__________________________________________________ _______

This fellow was planning to put his antenna on the roof of a car.
Presumably he is *not* DXing.

I was therefore speaking of groundwave coverage, not any kind of skip,
and what I stated holds true; for local groundwave, vertical is best.

DXers, on the other hand, use horizontal precisely because the local
groundwave coverage is poor, thereby reducing local QRM but having
little or no effect on skip signals.

--
Bill, W6WRT
QSLs via LoTW

Dale Parfitt wrote:

I wasn't talking about skip either- the majority of V/U weak signal work is
extended ground wave via perhaps enhanced tropo.

Ground wave? Really? I admit I'm not a propagation expert, so I'd
appreciate an explanation from someone who is. Is there really enough
ground wave propagation at VHF/UHF to be useful for any purpose, even
short range communication?

1.Horizontal polarity can take advantage of ground gain reflection that
vertical polarity cannot.

2. In addition, at 900 MHz where a wavelength is just over a foot, even
mounting the antenna at 12" would place the first lobe at 15 degrees,
assuming the car roof completely determines this- and I doubt that it has
much of an effect on far field take off angle.

You'd get that 15 degree lobe only if the roof extends far enough from
the antenna to reflect a wave going out at an angle 15 degrees below the
horizon (plus a bit, because the reflection doesn't actually take place
from a single point). At 12" above the car roof, the 15 degree downward
wave strikes the roof 12/tan(15 deg.) ~ 45 inches from the point below
the antenna. So the the car roof would have to extend at least about 4
feet beyond the antenna in the direction you're sending in order to get
that 15 degree lobe with the antenna 12" above the roof.

Roy Lewallen, W7EL

Have you tried an halo or loop antenna? M2 Antenna's and Par Electronics makes
them. Homebrew plans are on the net.

The halo is a 1/2 wave dipole bent into a circle. Common designs use 1 turn,
but 3 turn halo's have been used, with more gain. Stacking 2 halo's also
provide additional gain. Weak signal operaters on VHF and UHF use them mobile
on a regular basis.

Randy ka4nma

Roy Lewallen wrote:
Dale Parfitt wrote:
I wasn't talking about skip either- the majority of V/U weak signal
work is
extended ground wave via perhaps enhanced tropo.

Ground wave? Really? I admit I'm not a propagation expert, so I'd
appreciate an explanation from someone who is. Is there really enough
ground wave propagation at VHF/UHF to be useful for any purpose, even
short range communication?

No, it isn't ground wave at all. It's just a loose way of saying "normal
short-range VHF/UHF propagation" which is a complex combination of
line-of-sight, diffraction and scattering.

At medium ranges - which can be several hundred miles between
well-equipped stations - atmospheric refraction and scattering are the
main mechanisms. When weather systems lead to an "opening", signal
strengths and workable ranges are enhanced by much stronger refraction
and ducting.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

In message , "Ian White, G3SEK"
writes
Roy Lewallen wrote:
Dale Parfitt wrote:
I wasn't talking about skip either- the majority of V/U weak signal
work is
extended ground wave via perhaps enhanced tropo.

Ground wave? Really? I admit I'm not a propagation expert, so I'd
appreciate an explanation from someone who is. Is there really enough
ground wave propagation at VHF/UHF to be useful for any purpose, even
short range communication?

No, it isn't ground wave at all. It's just a loose way of saying
"normal short-range VHF/UHF propagation" which is a complex combination
of line-of-sight, diffraction and scattering.

At medium ranges - which can be several hundred miles between
well-equipped stations - atmospheric refraction and scattering are the
main mechanisms. When weather systems lead to an "opening", signal
strengths and workable ranges are enhanced by much stronger refraction
and ducting.



When I was a lad, I learned that the 'goundwave' requires the flow of
current in the ground, and is intimately tied up with the ground
conductivity. Its attenuation rises rapidly as frequency increases, so
is essentially only a low-frequency phenomenon. It requires a vertical
antenna.

Propagation at the higher frequencies is via 'spacewave', which has
nothing to do with currents flowing in the ground.

Many years ago, there were lots of discussions about whether vertical or
horizontal polarisation went further. In the UK, many of the (no longer
used) VHF TV transmitters used vertical. I don't think that the US ever
used vertical for TV. I think that the verdict eventually was that
horizontal won by a very short head.

At UHF, horizontal is invariably used for the high power TV
transmitters, and the low-power fill-ins nearly always use vertical.
There is therefore little opportunity to make a practical comparison of
which polarisation is consistently received at great distances - it's
always horizontal.

As for short range mobile and portable communications, propagation
relies so much on 'bouncing off things' that it probably doesn't matter.
Circular is probably best, but vertical physically easier. I can't
imagine why anyone would want to use horizontal.

Cheers,
Ian.
--

I use a horizontal omnidirectional antenna for 2M in the truck while
working SSB. Most home-based 2M SSB stations run horizontal
polarization (at least here in the USA). I use it to help avoid the 20
dB or so loss that occurs from crossed polarization.


Ian Jackson wrote:


As for short range mobile and portable communications, propagation
relies so much on 'bouncing off things' that it probably doesn't matter.
Circular is probably best, but vertical physically easier. I can't
imagine why anyone would want to use horizontal.

Cheers,
Ian.

--
Scott
http://corbenflyer.tripod.com/
Building RV-4
Gotta Fly or Gonna Die

Ian Jackson wrote:

As for short range mobile and portable communications, propagation
relies so much on 'bouncing off things' that it probably doesn't
matter. Circular is probably best, but vertical physically easier. I
can't imagine why anyone would want to use horizontal.
Cheers,
Ian.

In message , Scott
writes
I use a horizontal omnidirectional antenna for 2M in the truck while
working SSB. Most home-based 2M SSB stations run horizontal
polarization (at least here in the USA). I use it to help avoid the 20
dB or so loss that occurs from crossed polarization.



Same here in the UK. However, SSB is generally associated with longer
distance working (for lots of reasons), and folks tend to have larger
antennas then for local ragchews on FM (often through a repeater). If
you have a large antenna, it's physically easier to make it horizontal
(eg fewer problems with mounting it and avoiding the mast). If you
regularly work the SSB guys, you would certainly want to use horizontal
when mobile, especially as SSB is much less forgiving than FM is to the
deep and rapid flutter that is accentuated by cross-polarisation.
However, I think it's not so much a case of 'wanting' to use horizontal,
it's more like 'having' to.
Ian.
--

"Roy Lewallen" wrote in message
...
Dale Parfitt wrote:

I wasn't talking about skip either- the majority of V/U weak signal work
is
extended ground wave via perhaps enhanced tropo.

Ground wave? Really? I admit I'm not a propagation expert, so I'd
appreciate an explanation from someone who is. Is there really enough
ground wave propagation at VHF/UHF to be useful for any purpose, even
short range communication?

Thank you for the reflection explaination Roy- the geometry makes perect
sense.

As for the ground wave- perhaps I am using the wrong term in describing the
regular (non enhanced) communications that takes place on 6M and up.
On 6M I can regularly work out to 300 miles or so w/o the aid of sporadic E,
aurora or other ionospherically propogated signals.
The ARRL Antenna Handbook describes ground wave as:
"...any wave that stays close to the earth, reaching the receiving point
without leaving the earth's lower atmosphere."

Kraus doesn't address VHF ground wave that I can see.

Perhaps scatter mode might be a better description- in this case tropo
scatter.

73,

Dale W4OP

"Theplanters95" wrote in message
...
Have you tried an halo or loop antenna? M2 Antenna's and Par Electronics
makes
them. Homebrew plans are on the net.

The halo is a 1/2 wave dipole bent into a circle. Common designs use 1
turn,
but 3 turn halo's have been used, with more gain. Stacking 2 halo's also
provide additional gain. Weak signal operaters on VHF and UHF use them
mobile
on a regular basis.

Randy ka4nma

Two points of clarification. The PAR design is not a half wave antenna. It
is longer than a half wave- that length combined with the isosceles triangle
shape yields an excellent omni pattern and a bit more BW

The 3 loop haloes were not 3 turns. The loops were configured as a folded
dipole in order to increase the inherently low feedpoint R (10-15 Ohms) of a
single loop. There is no increase in gain from doing this.

Dale W4OP

Dale Parfitt wrote:
The ARRL Antenna Handbook describes ground wave as:"...any wave that
stays close to the earth, reaching the receiving point without leaving
the earth's lower atmosphere."

That definition is very misleading at VHF, since normal tropospheric
refraction takes place entirely in "the earth's lower atmosphere" but
generally doesn't involve ground at all. It's a gradual bending of the
space wave.

Kraus doesn't address VHF ground wave that I can see.

Perhaps scatter mode might be a better description- in this case tropo
scatter.

That isn't quite it, either, because "scatter" has a specific meaning
which doesn't fully apply to this complex (and varying) mixture of
propagation modes. In fact, no attempt to label VHF/UHF propagation as
one single mode can ever be correct.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Dale Parfitt wrote:
As for the ground wave- perhaps I am using the wrong term in describing the
regular (non enhanced) communications that takes place on 6M and up.

From the IEEE Dictionary:

"The ground wave can be decomposed into the Norton surface
wave and a space wave consisting of the vector sum of a
direct wave and a ground-reflected wave."

Looks like you are using the correct term and others may
not be.
--
73, Cecil http://www.qsl.net/w5dxp


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Ian White, G3SEK wrote:

Dale Parfitt wrote:
The ARRL Antenna Handbook describes ground wave as:"...any wave that
stays close to the earth, reaching the receiving point without leaving
the earth's lower atmosphere."

That definition is very misleading at VHF, since normal tropospheric
refraction takes place entirely in "the earth's lower atmosphere" but
generally doesn't involve ground at all. It's a gradual bending of the
space wave.

Yep, the IEEE Dictionary says the "ground wave" possesses a
space wave component. "From a source in the vicinity of the
surface of the Earth, a wave that would exist in the vicinity
of the surface in the absence of an ionosphere. The ground wave
can be decomposed into the Norton surface wave and a space wave
consisting of the vector sum of a direct wave and a ground-
reflected wave."
--
73, Cecil http://www.qsl.net/w5dxp


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Roy Lewallen wrote:

I sense there's still a failure to communicate.

If Dale means by "V/U" VHF and UHF, ground wave isn't a viable means of
propagation anyway.

Maybe you could revise your definition of "ground wave" to
agree with the IEEE? The IEEE dictionary says the "ground wave"
is defined to be what would be left if we took away the ionosphere.
It says the ground wave *includes* a component of the space wave.
--
73, Cecil http://www.qsl.net/w5dxp


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Cecil Moore wrote:
Ian White, G3SEK wrote:

Dale Parfitt wrote:
The ARRL Antenna Handbook describes ground wave as:"...any wave that
stays close to the earth, reaching the receiving point without
leaving the earth's lower atmosphere."

That definition is very misleading at VHF, since normal tropospheric
refraction takes place entirely in "the earth's lower atmosphere" but
generally doesn't involve ground at all. It's a gradual bending of the
space wave.

Yep, the IEEE Dictionary says the "ground wave" possesses a
space wave component. "From a source in the vicinity of the
surface of the Earth, a wave that would exist in the vicinity
of the surface in the absence of an ionosphere. The ground wave
can be decomposed into the Norton surface wave and a space wave
consisting of the vector sum of a direct wave and a ground-
reflected wave."

Thank you - that's a new one to me.

So what does the IEEE define a "Norton surface wave" to be?


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

"Roy Lewallen" wrote in message
...
I sense there's still a failure to communicate.

If Dale means by "V/U" VHF and UHF, ground wave isn't a viable means of
propagation anyway. The attenuation of ground waves increases with
frequency, to the point that they're virtually useless at VHF and above.
So at those frequencies, I'd think the polarization choice for short
range communication would be based on how it affects attenuation,
multipath, and QRM. Given those criteria, horizontal might well have an
advantage for short range communication, in some locations at least. And
it's long been favored for long range VHF/UHF communication.


Ground wave is a broad term, but it is how VHF and UHF usually propagate.
Ground wave is a general term for several means of propagation. Surface
wave is what you are really talking about when you mention Ground wave.
Space wave, atmosphere ducts and other means near the earth are all part of
the Ground wave term. The Sky wave is usually the broad term for
reflections off the ionosphere and other reflected modes from high above the
surface.

For vertical or horizontal there is very little differance in which is used
at VHF and above. Noise is usually vertical polorised so horizontal for the
RF is usually used . Vertical is used so the simple vertical moble whips
could be used for all around coverage.

Ian White, G3SEK wrote:
So what does the IEEE define a "Norton surface wave" to be?

"Norton surface wave - a guided EM wave produced by a source
over or on the ground. It is the non-geometrical optics
component of the ground wave."

"geometric optics - the treatment of propagation of light as
rays. Note: Rays are bent at the interface between two dissimilar
media or may be curved in a medium in which refractive index is a
function of position."

Presumably, there are no geometric optics involved in RF emissions
from an antenna. Therefore, for an RF antenna, the Norton wave
equals the surface wave. The surface wave and ground wave are
NOT the same thing. Besides the surface wave, the ground wave
contains part of the space wave which itself consists of two
parts, direct and ground-reflected.

So according to the IEEE, it is not ground wave Vs sky wave.
It is surface wave Vs sky wave. Ground wave = part surface
wave and part sky wave.
--
73, Cecil http://www.qsl.net/w5dxp


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Andrey wrote:
"I want to create horizontally polarized antenna, low profile, located
above large ground plane. And I need it to be omnidirectional (sort of)
and have sufficient gain in horizontal plane.

My frequency of interest is 900 MHz. The ground plane is a roof of a
car."

A horizontal dipole above a metal car roof is a poor choice.

Polarization choice at 900 MHz does not affect signal range.

In the horizontal plane, the direct signal broadside to the dipole is
cancelled by the reflected signal from the roof unless you elevate the
dipole by 50 cm or so at 900 MHz. That`s almost 2 wavelengths. At that
height, the omnidirectionality may not be even "sort of".

Better to use a vertical which has a signal null off its tip and maximum
radiation in the horizontal plane. This can be a collinear made of
1/2-wave sections separated by 1/4-wave stub(s) for gain. As the
wavelength is only 34 centimeters, this isn`t much of a problem. It
could be made by bending a single length of stiff wire.

Best regards, Richard Harrison, KB5WZI

Thanks to all who responded. I see I've been misusing "ground wave" for
a long time, in place of "surface wave". And my apology to those I've
questioned about "ground wave" propagation at VHF/UHF. According to
correct usage, it does indeed exist -- just not with a surface wave
component.

Roy Lewallen, W7EL

Hi Dale,

Are you saying that the old saturn halo was not 3 loops? It sure looks like it
in the pictures that I have seen.

I know that your design (the Par Omniangle) is not the classic 1/2 wave halo,
and does offer more advantages over a halo. I sure wish I had a 2m and 6m for
the upcoming VHF contest.

Randy ka4nma

Roy Lewallen wrote:
Thanks to all who responded. I see I've been misusing "ground wave" for
a long time, in place of "surface wave". And my apology to those I've
questioned about "ground wave" propagation at VHF/UHF. According to
correct usage, it does indeed exist -- just not with a surface wave
component.

Likewise, my apologies to anyone whom I've misled.

But I apologise with fingers crossed behind my back!

The IEEE Dictionary mavens have produced a very HF-centric definition of
"ground wave", by defining it to include all modes of propagation except
"sky wave"; where "sky" is exclusively defined as "ionospheric".

This definition completely ignores all the non-ionospheric VHF/UHF
propagation modes that don't involve the ground at all.

Since a misleading definition is worse than no definition at all, the
best policy for the term "ground wave" is to label it "Broken - Do Not
Use".


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Ian, G3SEK wrote:
"The IEEE Dictionary mavens have produced a very HF-cebtric definition
of "ground wave"."

Regretable. Seems clear that a ground wave would require interaction
with the ground. According to Terman it does. On page 803 of his 1955
edition, Terman says:

"The "ground wave" (also sometimes called surface wave) can exist when
the transmitting and receiving antennas are close to the surface of the
earth and are vertically polarized. This wave, supported at its lower
edge by the presence of the ground, is of practical importance at
broadcast and lower frequencies."

The ground wave requires the earth to participate in its propagation and
the earth gives the ground wave a continuation beyond the line-of-sight
without atmospheric or ionospheric intervention.

Best regards, Richard Harrison, KB5WZI

Ian White, G3SEK wrote:
The IEEE Dictionary mavens have produced a very HF-centric definition of
"ground wave", by defining it to include all modes of propagation except
"sky wave"; where "sky" is exclusively defined as "ionospheric".

"sky wave - a radio wave propagated obliquely toward, and returned from,
the ionosphere."

Apparently, if it's not returned from the ionosphere, it's not a
sky wave. That implies that the stars are not in the sky. :-)
--
73, Cecil http://www.qsl.net/w5dxp



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