wrote in message ...


For those that do not have a firm understanding of what the chart of
dipole height over ground shows, I offer the following explanation.

The charts show, for a dipole antenna at various heights in wavelengths
over perfect, very good, average, and extremely poor ground, the gain
and elevation angle of the antenna main lobe.

The main lobe is where the majority of the energy is radiated.

To understand what the charts mean in the real world, first you have
to understand a little bit about propagation of RF.

For a dipole antenna, there are two modes of propagation that are relevant,
and those are NVIS (Near Vertical Incidence Skywave) and skywave which
is sometimes called skip.

Both modes depend on the RF being reflected or refracted back toward
Earth by the ionosphere.

For NVIS mode, the RF is directed straight up, that is an elevation angle
close to 90 degrees is desired. The range of NVIS communications is on
the order of 50 - 650 km, depending on the state of the ionosphere. The
amateur bands where this is effective is limited primarily to the 160M
to 40M band, again depending on the state of the ionosphere. It is not
impossible to have NVIS communications on the higher bands, just much
less probable to happen.

For skywave mode, a low elevation mode is desired. Most of the literature
recommends angles of 30 degees or less. In this mode the RF "bounces"
at more obtuse angles, and with good conditions in the ionosphere, more
than once, providing communication over global distances. Skywave
depends heavily on the condition of the ionosphere and during sunspot
peaks often occurs well past 10M.

Now since a dipole with a main lobe at 90 degrees still has some gain
at low angles, though it can be 20 to 60 dB down from the main lobe,
when conditions are very good some stations can still be heard by
skywave mode, though it is a rarity and can not be depended on.

Conversely a dipole with a low elevation angle of the main lobe has some
gain at very high angles and can occasionly hear stations by NVIS mode,
but again it is a rarity.

The bottom line of all this is that if you desire NVIS communications,
you should mount your dipole at a height where the elevation angle is
close to 90 degrees while if you desire long distance communications
you should mount your dipole at a height where the elevation angle is
less than 30 degrees, or higher if possible.

If the required height is impractical at your location, then the
alternative is a ground mounted vertical or a close to ground mounted
ground plane antenna, which will have an elevation angle in the 20
degree range.

Along the lines of a "testimonial"...
I once lived in the center of a state that had an active 75 meter net. At
one point I was asked to be one of the net control stations because of my
consistent strong signals within the net.

The secret? A 75 meter dipole at 20 feet with 100 watts.
On longer paths, of course, the "big boys" kicked my butt big time.

In message , Wayne
writes


wrote in message ...


For those that do not have a firm understanding of what the chart of
dipole height over ground shows, I offer the following explanation.

The charts show, for a dipole antenna at various heights in wavelengths
over perfect, very good, average, and extremely poor ground, the gain
and elevation angle of the antenna main lobe.

The main lobe is where the majority of the energy is radiated.

To understand what the charts mean in the real world, first you have
to understand a little bit about propagation of RF.

For a dipole antenna, there are two modes of propagation that are relevant,
and those are NVIS (Near Vertical Incidence Skywave) and skywave which
is sometimes called skip.

Both modes depend on the RF being reflected or refracted back toward
Earth by the ionosphere.

For NVIS mode, the RF is directed straight up, that is an elevation angle
close to 90 degrees is desired. The range of NVIS communications is on
the order of 50 - 650 km, depending on the state of the ionosphere. The
amateur bands where this is effective is limited primarily to the 160M
to 40M band, again depending on the state of the ionosphere. It is not
impossible to have NVIS communications on the higher bands, just much
less probable to happen.

For skywave mode, a low elevation mode is desired. Most of the literature
recommends angles of 30 degees or less. In this mode the RF "bounces"
at more obtuse angles, and with good conditions in the ionosphere, more
than once, providing communication over global distances. Skywave
depends heavily on the condition of the ionosphere and during sunspot
peaks often occurs well past 10M.

Now since a dipole with a main lobe at 90 degrees still has some gain
at low angles, though it can be 20 to 60 dB down from the main lobe,
when conditions are very good some stations can still be heard by
skywave mode, though it is a rarity and can not be depended on.

Conversely a dipole with a low elevation angle of the main lobe has some
gain at very high angles and can occasionly hear stations by NVIS mode,
but again it is a rarity.

The bottom line of all this is that if you desire NVIS communications,
you should mount your dipole at a height where the elevation angle is
close to 90 degrees while if you desire long distance communications
you should mount your dipole at a height where the elevation angle is
less than 30 degrees, or higher if possible.

If the required height is impractical at your location, then the
alternative is a ground mounted vertical or a close to ground mounted
ground plane antenna, which will have an elevation angle in the 20
degree range.

Along the lines of a "testimonial"...
I once lived in the center of a state that had an active 75 meter net.
At one point I was asked to be one of the net control stations because
of my consistent strong signals within the net.

The secret? A 75 meter dipole at 20 feet with 100 watts.
On longer paths, of course, the "big boys" kicked my butt big time.

Despite the obvious theory, and over 50 years in amateur radio, I still
find it hard to believe that, in real life, an 80m dipole at (say) 20'
ever really outperforms (at any distance) one at (say) 100'. Given the
choice, I know which one I would choose!
--
Ian

Ian Jackson wrote:

snip

Despite the obvious theory, and over 50 years in amateur radio, I still
find it hard to believe that, in real life, an 80m dipole at (say) 20'
ever really outperforms (at any distance) one at (say) 100'. Given the
choice, I know which one I would choose!

Try reading these:

http://www.qsl.net/wb5ude/nvis/
http://en.wikipedia.org/wiki/Near_ve...idence_skywave
http://www.w0ipl.net/ECom/NVIS/nvis.htm
http://kv5r.com/ham-radio/nvis-antennas/
http://www.arrl.org/nvis


--
Jim Pennino

In message ,
writes
Ian Jackson wrote:

snip

Despite the obvious theory, and over 50 years in amateur radio, I still
find it hard to believe that, in real life, an 80m dipole at (say) 20'
ever really outperforms (at any distance) one at (say) 100'. Given the
choice, I know which one I would choose!

Try reading these:

http://www.qsl.net/wb5ude/nvis/
http://en.wikipedia.org/wiki/Near_ve...idence_skywave
http://www.w0ipl.net/ECom/NVIS/nvis.htm
http://kv5r.com/ham-radio/nvis-antennas/
http://www.arrl.org/nvis

Thanks, I'll certainly have a good read of those articles. But
regardless of what they say, in a typical amateur scenario, I still
reckon that at (say) 300 miles, an 80m signal from a dipole at 100' is
likely to be stronger than one from one at 20' (or even at 60').


--
Ian

Ian Jackson wrote:
In message ,
writes
Ian Jackson wrote:

snip

Despite the obvious theory, and over 50 years in amateur radio, I still
find it hard to believe that, in real life, an 80m dipole at (say) 20'
ever really outperforms (at any distance) one at (say) 100'. Given the
choice, I know which one I would choose!

Try reading these:

http://www.qsl.net/wb5ude/nvis/
http://en.wikipedia.org/wiki/Near_ve...idence_skywave
http://www.w0ipl.net/ECom/NVIS/nvis.htm
http://kv5r.com/ham-radio/nvis-antennas/
http://www.arrl.org/nvis

Thanks, I'll certainly have a good read of those articles. But
regardless of what they say, in a typical amateur scenario, I still
reckon that at (say) 300 miles, an 80m signal from a dipole at 100' is
likely to be stronger than one from one at 20' (or even at 60').

As 300 miles is at the upper end of NVIS and the lower end for skywave,
it would be a crap shoot.

NVIS distance is typically 30-400 miles.

--
Jim Pennino

In message ,
writes
Ian Jackson wrote:
In message ,
writes
Ian Jackson wrote:

snip

Despite the obvious theory, and over 50 years in amateur radio, I still
find it hard to believe that, in real life, an 80m dipole at (say) 20'
ever really outperforms (at any distance) one at (say) 100'. Given the
choice, I know which one I would choose!

Try reading these:

http://www.qsl.net/wb5ude/nvis/
http://en.wikipedia.org/wiki/Near_ve...idence_skywave
http://www.w0ipl.net/ECom/NVIS/nvis.htm
http://kv5r.com/ham-radio/nvis-antennas/
http://www.arrl.org/nvis

Thanks, I'll certainly have a good read of those articles. But
regardless of what they say, in a typical amateur scenario, I still
reckon that at (say) 300 miles, an 80m signal from a dipole at 100' is
likely to be stronger than one from one at 20' (or even at 60').

As 300 miles is at the upper end of NVIS and the lower end for skywave

NVIS IS skywave - only that it's more straight up-and-down than at an
angle. It's only a matter (literally) of degree, and there's no real
point at which NVIS becomes 'normal' skywave.
,
it would be a crap shoot.

NVIS distance is typically 30-400 miles.

OK, let's make it a bit less - say 50 or 100 miles. I still feel that,
in practice, a dipole at 100' would be unlikely to be less effective
than at 20'.

On the other hand, if you only want to lay down a signal out to less
than 400 miles, there's no point in going to the trouble of putting the
dipole at 100'. Apart from cost etc, this would also unnecessarily cause
QRM to reception outside your intended target area.


--
Ian

Ian Jackson wrote:
In message ,
writes
Ian Jackson wrote:
In message ,
writes
Ian Jackson wrote:

snip

Despite the obvious theory, and over 50 years in amateur radio, I still
find it hard to believe that, in real life, an 80m dipole at (say) 20'
ever really outperforms (at any distance) one at (say) 100'. Given the
choice, I know which one I would choose!

Try reading these:

http://www.qsl.net/wb5ude/nvis/
http://en.wikipedia.org/wiki/Near_ve...idence_skywave
http://www.w0ipl.net/ECom/NVIS/nvis.htm
http://kv5r.com/ham-radio/nvis-antennas/
http://www.arrl.org/nvis

Thanks, I'll certainly have a good read of those articles. But
regardless of what they say, in a typical amateur scenario, I still
reckon that at (say) 300 miles, an 80m signal from a dipole at 100' is
likely to be stronger than one from one at 20' (or even at 60').

As 300 miles is at the upper end of NVIS and the lower end for skywave

NVIS IS skywave - only that it's more straight up-and-down than at an
angle. It's only a matter (literally) of degree, and there's no real
point at which NVIS becomes 'normal' skywave.

NVIS is generally defined as aiming the power straight up and the S
in NVIS stands for "Skywave". So if you want to be pendatic, you are
correct.

However, if you look at the links above, the real world DOES make
a distinction between NVIS and skywave.

it would be a crap shoot.

NVIS distance is typically 30-400 miles.

OK, let's make it a bit less - say 50 or 100 miles. I still feel that,
in practice, a dipole at 100' would be unlikely to be less effective
than at 20'.

The experience of all the world's militaries and those others who have
done actual measurements come to a contrary conclusion.


--
Jim Pennino

On 11/22/2014 7:21 AM, Ian Jackson wrote:
In message ,
writes
Ian Jackson wrote:

snip

Despite the obvious theory, and over 50 years in amateur radio, I still
find it hard to believe that, in real life, an 80m dipole at (say) 20'
ever really outperforms (at any distance) one at (say) 100'. Given the
choice, I know which one I would choose!

Try reading these:

http://www.qsl.net/wb5ude/nvis/
http://en.wikipedia.org/wiki/Near_ve...idence_skywave
http://www.w0ipl.net/ECom/NVIS/nvis.htm
http://kv5r.com/ham-radio/nvis-antennas/
http://www.arrl.org/nvis

Thanks, I'll certainly have a good read of those articles. But
regardless of what they say, in a typical amateur scenario, I still
reckon that at (say) 300 miles, an 80m signal from a dipole at 100' is
likely to be stronger than one from one at 20' (or even at 60').



Yes,

intuitively it certainly seems like the higher antenna will perform
better. However, I have a chart about loop antennas that rates the 75
meter loop highest in NVIS gain at 25 feet high. I included the pdf file
if it comes through. Mine at 33 feet makes a pretty good NVIS antenna.
Will never know what it would do at 100 feet.

On Friday, November 21, 2014 4:47:12 PM UTC-6, Ian Jackson wrote:
In message , Wayne
writes


wrote in message ...


For those that do not have a firm understanding of what the chart of
dipole height over ground shows, I offer the following explanation.

The charts show, for a dipole antenna at various heights in wavelengths
over perfect, very good, average, and extremely poor ground, the gain
and elevation angle of the antenna main lobe.

The main lobe is where the majority of the energy is radiated.

To understand what the charts mean in the real world, first you have
to understand a little bit about propagation of RF.

For a dipole antenna, there are two modes of propagation that are relevant,
and those are NVIS (Near Vertical Incidence Skywave) and skywave which
is sometimes called skip.

Both modes depend on the RF being reflected or refracted back toward
Earth by the ionosphere.

For NVIS mode, the RF is directed straight up, that is an elevation angle
close to 90 degrees is desired. The range of NVIS communications is on
the order of 50 - 650 km, depending on the state of the ionosphere. The
amateur bands where this is effective is limited primarily to the 160M
to 40M band, again depending on the state of the ionosphere. It is not
impossible to have NVIS communications on the higher bands, just much
less probable to happen.

For skywave mode, a low elevation mode is desired. Most of the literature
recommends angles of 30 degees or less. In this mode the RF "bounces"
at more obtuse angles, and with good conditions in the ionosphere, more
than once, providing communication over global distances. Skywave
depends heavily on the condition of the ionosphere and during sunspot
peaks often occurs well past 10M.

Now since a dipole with a main lobe at 90 degrees still has some gain
at low angles, though it can be 20 to 60 dB down from the main lobe,
when conditions are very good some stations can still be heard by
skywave mode, though it is a rarity and can not be depended on.

Conversely a dipole with a low elevation angle of the main lobe has some
gain at very high angles and can occasionly hear stations by NVIS mode,
but again it is a rarity.

The bottom line of all this is that if you desire NVIS communications,
you should mount your dipole at a height where the elevation angle is
close to 90 degrees while if you desire long distance communications
you should mount your dipole at a height where the elevation angle is
less than 30 degrees, or higher if possible.

If the required height is impractical at your location, then the
alternative is a ground mounted vertical or a close to ground mounted
ground plane antenna, which will have an elevation angle in the 20
degree range.

Along the lines of a "testimonial"...
I once lived in the center of a state that had an active 75 meter net.
At one point I was asked to be one of the net control stations because
of my consistent strong signals within the net.

The secret? A 75 meter dipole at 20 feet with 100 watts.
On longer paths, of course, the "big boys" kicked my butt big time.

Despite the obvious theory, and over 50 years in amateur radio, I still
find it hard to believe that, in real life, an 80m dipole at (say) 20'
ever really outperforms (at any distance) one at (say) 100'. Given the
choice, I know which one I would choose!
--
Ian

Dunno.. I've run some pretty low dipoles that did well for NVIS paths.
Mostly when camping. I had one out at Lake Amistad that was about 8 ft
off the ground, and I was only running 10w out with a FT-7. I was S9
or slightly over to most of the other guys in the state.

When I'm at the dirt patch my dipole is usually only about 25 ft or so
at the apex, and it does fairly well as long as the band is not buggered
up, which happens quite a bit in the early evening, or in the winter
when the MUF drops down real low.
Saying that, I would probably choose the high dipole also if I had a
choice. It would still do OK for NVIS, and a lot better than the low
one on DX paths.

On 11/21/2014 5:47 PM, Ian Jackson wrote:
In message , Wayne
writes


wrote in message ...


For those that do not have a firm understanding of what the chart of
dipole height over ground shows, I offer the following explanation.

The charts show, for a dipole antenna at various heights in wavelengths
over perfect, very good, average, and extremely poor ground, the gain
and elevation angle of the antenna main lobe.

The main lobe is where the majority of the energy is radiated.

To understand what the charts mean in the real world, first you have
to understand a little bit about propagation of RF.

For a dipole antenna, there are two modes of propagation that are
relevant,
and those are NVIS (Near Vertical Incidence Skywave) and skywave which
is sometimes called skip.

Both modes depend on the RF being reflected or refracted back toward
Earth by the ionosphere.

For NVIS mode, the RF is directed straight up, that is an elevation
angle
close to 90 degrees is desired. The range of NVIS communications is on
the order of 50 - 650 km, depending on the state of the ionosphere. The
amateur bands where this is effective is limited primarily to the 160M
to 40M band, again depending on the state of the ionosphere. It is not
impossible to have NVIS communications on the higher bands, just much
less probable to happen.

For skywave mode, a low elevation mode is desired. Most of the
literature
recommends angles of 30 degees or less. In this mode the RF "bounces"
at more obtuse angles, and with good conditions in the ionosphere, more
than once, providing communication over global distances. Skywave
depends heavily on the condition of the ionosphere and during sunspot
peaks often occurs well past 10M.

Now since a dipole with a main lobe at 90 degrees still has some gain
at low angles, though it can be 20 to 60 dB down from the main lobe,
when conditions are very good some stations can still be heard by
skywave mode, though it is a rarity and can not be depended on.

Conversely a dipole with a low elevation angle of the main lobe has some
gain at very high angles and can occasionly hear stations by NVIS mode,
but again it is a rarity.

The bottom line of all this is that if you desire NVIS communications,
you should mount your dipole at a height where the elevation angle is
close to 90 degrees while if you desire long distance communications
you should mount your dipole at a height where the elevation angle is
less than 30 degrees, or higher if possible.

If the required height is impractical at your location, then the
alternative is a ground mounted vertical or a close to ground mounted
ground plane antenna, which will have an elevation angle in the 20
degree range.

Along the lines of a "testimonial"...
I once lived in the center of a state that had an active 75 meter net.
At one point I was asked to be one of the net control stations because
of my consistent strong signals within the net.

The secret? A 75 meter dipole at 20 feet with 100 watts.
On longer paths, of course, the "big boys" kicked my butt big time.

Despite the obvious theory, and over 50 years in amateur radio, I still
find it hard to believe that, in real life, an 80m dipole at (say) 20'
ever really outperforms (at any distance) one at (say) 100'. Given the
choice, I know which one I would choose!

I never said a dipole at 20' outperforms one at 100'. But I DID say a
dipole at 20' does NOT necessarily "suck". It can be a good antenna,
depending on a lot of other factors.

I've also run dipoles - I got WAS on 75 meters from Iowa with an
inverted VEE running from 50' to near ground. And I had a strong signal
on the Iowa 75M SSB net.

Doesn't sound like it "sucked" to me.

--
==================
Remove the "x" from my email address
Jerry, AI0K

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