Poor vertical performance on metal sheet roof - comments?
 

I just finished putting up a 6m long aluminum tube for a vertical for
10/15/20m. Its length is just over 1/4 wavelength on 20m and just
under 5/8 wavelengths on 10m. The vertical is located at the apex (8m
above ground) of a sheet metal roof top, that slopes approx. 30
degrees down to all sides from the vertical. I use use the roof metal
as a counterpoise and feed the vertical with an autotuner at the base.
A coax runs 6m (18ft) from the autotuner, down through an attic
window and to my TX.

Now, simulations (EZNEC 3.0) and common wisdom predict a fairly good
performance for this antenna. Not so. When the tuner is set for 1:1
VSWR the RX signals from the vertical on 15m are consistently 4
S-units below a 20m (60ft) long sloper at the corner of the house. I
use this sloper for 160m and 80m. When going to the 20m band the
vertical is about 8 S-units below the sloper. Even more irritating,
the vertical is constantly outperformed by a leftover horizontal wire,
approx. 6m long, lifted only 1m (3ft) above the roof.

Switching to the vertical from either wire antenna the background
noise and signals drop noticably. This led me to check out the tuner,
the feedline, connections, but all seems to be fine. The bottom line
appears to be that the vertical is simply a much poorer antenna than
either of the wires I have up already - contrary to the theory and
conventional wisdom.

Any comments, anyone, before I remove the vertical and turn to another
design?

73 de TF3KX, Kristinn

"Kristinn Andersen" wrote in message
om...
I just finished putting up a 6m long aluminum tube for a vertical for
10/15/20m. Its length is just over 1/4 wavelength on 20m and just
under 5/8 wavelengths on 10m. The vertical is located at the apex (8m
above ground) of a sheet metal roof top, that slopes approx. 30
degrees down to all sides from the vertical. I use use the roof metal
as a counterpoise and feed the vertical with an autotuner at the base.
A coax runs 6m (18ft) from the autotuner, down through an attic
window and to my TX.

Now, simulations (EZNEC 3.0) and common wisdom predict a fairly good
performance for this antenna. Not so. When the tuner is set for 1:1
VSWR the RX signals from the vertical on 15m are consistently 4
S-units below a 20m (60ft) long sloper at the corner of the house. I
use this sloper for 160m and 80m. When going to the 20m band the
vertical is about 8 S-units below the sloper. Even more irritating,
the vertical is constantly outperformed by a leftover horizontal wire,
approx. 6m long, lifted only 1m (3ft) above the roof.

Switching to the vertical from either wire antenna the background
noise and signals drop noticably. This led me to check out the tuner,
the feedline, connections, but all seems to be fine. The bottom line
appears to be that the vertical is simply a much poorer antenna than
either of the wires I have up already - contrary to the theory and
conventional wisdom.

Any comments, anyone, before I remove the vertical and turn to another
design?

73 de TF3KX, Kristinn

Kristinn
Can you get on the roof with an antenna analyzer and see what the vertical
looks like to the tuner?
Are you certain the roof is electrically continuous?
H.
NQ5H

Kristinn,

I'd try measuring SWR and impedance at the base of the antenna and also ensure
that connections to the roof, particularly between the various sections, all
have good cotinuity. There is a chance that there is rust and corrosion
between overlapping sections.

73s,

Evan

Any comments, anyone, before I remove the vertical and turn to another
design?

73 de TF3KX, Kristinn



First I would check the coax and tuner performance, make sure you have no bad
connections.
When comparing signals against other antennas, keep in mind that vertical is
better performer at low angles - DX. Try the comparison on DX signals rather
than Eu and high angle propagation. You could esay see 20 dB differences, but
check at the beginning of openings to DX areas and see how they compare.

GL Yuri, K3BU

Kristinn Andersen wrote:
Any comments, anyone, before I remove the vertical and turn to another
design?

I spent considerable time and effort erecting a 33ft vertical 40m
antenna with 8 elevated radials at 20ft. Average signal strengths were
about 2 S-units below a dipole and the noise level was about 2 S-units
higher than the dipole. At my QTH, it was a dog.
--
73, Cecil http://www.qsl.net/w5dxp



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Kristinn,

Before you decide to remove it, I would see if it can be made to resonate on
20 meters by itself. Ditch the tuner, and see how it performs. As somebody
suggested, see what it does with a ZL or VK, or even W6. I never had any
luck with 20m verticals myself, but talked to an G station on 20 SSB a few
days ago who was using one; sounded fine.

BTW, here is an odd one. I once had a 40 meter vertical with the feedpoint
at about 30 feet and 4 radials, sloping down at about 45 deg. At the same
time I had a 40m dipole at about 50 feet. I made tests with two groups of
hams. The one group was about 400 miles away, the other group about 1100
miles. Without exception, in each group people with verticals preferred my
vertical, and people with horizontal antennas preferred my dipole. Yes, I
know all about polarization not being important for a skywave signal.

Tam/WB2TT
"Kristinn Andersen" wrote in message
om...
I just finished putting up a 6m long aluminum tube for a vertical for
10/15/20m. Its length is just over 1/4 wavelength on 20m and

Mark Keith wrote:
. . .
Also, I suspect excess loss if the noise and signals drop compared to
any other antenna. If the coax is not bad, old or waterlogged, or thin
stuff like rg-58, then I'd suspect excess loss in the autotuner. . . .

Out of curiosity, just how much loss do you think "thin stuff like
RG-58", say 50 feet of it, has on 20 meters?

Roy Lewallen, W7EL

W5DXP wrote in message ...
Kristinn Andersen wrote:
Any comments, anyone, before I remove the vertical and turn to another
design?

I spent considerable time and effort erecting a 33ft vertical 40m
antenna with 8 elevated radials at 20ft. Average signal strengths were
about 2 S-units below a dipole and the noise level was about 2 S-units
higher than the dipole. At my QTH, it was a dog.

I had exactly the opposite results. It was 2-3 S units better at low
angles of radiation compared to my low dipole. I've heard other
experiences like this too. I just wonder if there some part of antenna
theory that's missing that could explain why that happens. Murphy's
law, blind luck, who knows. 8-)

73!

Jeff

For horizontal antennas -- the radiation angle becomes lower as the height
of the antenna increases and vice versa (with caveats)
A layman's explanation at URL:
http://www.signalengineering.com/ult...radiation.html

Excuse the CB reference -- but it has some nice pictorials.

Those mathematically inclined can model antennas at URL:
http://www.eznec.com/

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

"Jeffdeham" wrote in message
om...
W5DXP wrote in message
...
Kristinn Andersen wrote:
Any comments, anyone, before I remove the vertical and turn to another
design?

I spent considerable time and effort erecting a 33ft vertical 40m
antenna with 8 elevated radials at 20ft. Average signal strengths were
about 2 S-units below a dipole and the noise level was about 2 S-units
higher than the dipole. At my QTH, it was a dog.

I had exactly the opposite results. It was 2-3 S units better at low
angles of radiation compared to my low dipole. I've heard other
experiences like this too. I just wonder if there some part of antenna
theory that's missing that could explain why that happens. Murphy's
law, blind luck, who knows. 8-)

73!

Jeff

Jeffdeham wrote:
I had exactly the opposite results. It was 2-3 S units better at low
angles of radiation compared to my low dipole. I've heard other
experiences like this too. I just wonder if there some part of antenna
theory that's missing that could explain why that happens. Murphy's
law, blind luck, who knows. 8-)

The vertically polarized noise in my neighborhood is the real killer
of verticals.
--
73, Cecil http://www.qsl.net/w5dxp



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The vertically polarized noise in my neighborhood is the real killer
of verticals.
--
73, Cecil http://www.qsl.net/w5dxp




Hmmm,
all the noisey appliances in the neighborhood are vertically polarized?
Trolling for another argument "threat" :-?

Yuri

Yuri Blanarovich wrote:
The vertically polarized noise in my neighborhood is the real killer
of verticals.

all the noisey appliances in the neighborhood are vertically polarized?

A very large power transformer mounted on a pole at the edge of my
property has a 35 foot ground wire running down the pole about 100 ft
from my vertical. I suspect that is the source of the vertically
polarized noise.
--
73, Cecil http://www.qsl.net/w5dxp



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all the noisey appliances in the neighborhood are vertically polarized?

A very large power transformer mounted on a pole at the edge of my
property has a 35 foot ground wire running down the pole about 100 ft
from my vertical. I suspect that is the source of the vertically
polarized noise.
--
73, Cecil http://www.qsl.net/w5dxp



and no horizontal wires attached to it?
Is transformer producing noise? Or bad connections, arcing?
Mabee vertical antenna due to its pattern is "seeing" more noise than your
ladder fed wunderdipole?

I think there is a major misconception that verticals are more sensitive to
noise because the noise is "vertically polarized". Man made, appliance or
otherwise produced noise is "all kinds" polarized. It is the antenna's location
and radiation pattern that determines the amount of noise or S/N pick up.

Yuri

In article ,
Yuri Blanarovich wrote:

I think there is a major misconception that verticals are more sensitive to
noise because the noise is "vertically polarized". Man made, appliance or
otherwise produced noise is "all kinds" polarized. It is the antenna's location
and radiation pattern that determines the amount of noise or S/N pick up.

Well... yes and no (I think).

As I understand it, ground-wave / surface-wave propagation occurs for
vertically-polarized signals (or signal components), but not for
horizontally-polarized signals (or components). Even if manmade noise
is polarized in all planes with equal (or randomly distributed)
polarization senses, only the vertically polarized portion of it will
travel via groundwave propagation.

So, I suspect that the noise-proneness of vertical HF antennas
compared to horizontal dipoles, probably results from a "double
whammy". The horizontal antennas aren't exposed to anywhere near as
much energy propagating via groundwave (because horizontally-polarized
noise doesn't travel well in that mode), and they aren't as sensitive
to it because they often have fairly high radiation angles with a
substantial null towards the horizon.

The vertical antennas are hit with more noise energy, and due to their
low radiation angle they're pretty good at picking it up.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Roy Lewallen wrote in message ...
Mark Keith wrote:
. . .
Also, I suspect excess loss if the noise and signals drop compared to
any other antenna. If the coax is not bad, old or waterlogged, or thin
stuff like rg-58, then I'd suspect excess loss in the autotuner. . . .

Out of curiosity, just how much loss do you think "thin stuff like
RG-58", say 50 feet of it, has on 20 meters?

Roy Lewallen, W7EL

Normally it shouldn't be too much. But if the "thin" stuff is old, or
has been damaged , it might be more than usual. MK

Well, 50 feet of RG-58 has about 3/4 dB loss at 14 MHz. And when it's
old. . . I've got RG-58 that's well over 20 years old, and can't measure
the difference in loss between it and new cable. If it's damaged, it
might create an impedance bump, which you might or might not notice. But
that's true of larger diameter cable, too.

I'm bemused to find that today's hams have somehow gotten convinced they
all need BIG cable for a BIG signal. Maybe they've been listening to the
same ads that sell people on monster audio cables and SUVs. But I sure
hate to see this misleading concept being passed along to newcomers.
They'll fall for the ads soon enough without help.

Roy Lewallen, W7EL

Mark Keith wrote:
Roy Lewallen wrote in message ...

Mark Keith wrote:

. . .
Also, I suspect excess loss if the noise and signals drop compared to
any other antenna. If the coax is not bad, old or waterlogged, or thin
stuff like rg-58, then I'd suspect excess loss in the autotuner. . . .

Out of curiosity, just how much loss do you think "thin stuff like
RG-58", say 50 feet of it, has on 20 meters?

Roy Lewallen, W7EL


Normally it shouldn't be too much. But if the "thin" stuff is old, or
has been damaged , it might be more than usual. MK

Yuri Blanarovich wrote:
I think there is a major misconception that verticals are more sensitive to
noise because the noise is "vertically polarized". Man made, appliance or
otherwise produced noise is "all kinds" polarized. It is the antenna's location
and radiation pattern that determines the amount of noise or S/N pick up.

I'm just reporting what conditions exist at my QTH. There is approximately
two S-units higher noise on the vertical than on the horizontal. After weeks
of A/B comparisons, there was never a time or signal where the vertical appreciably
beat the horizontal. There were a few times when they were nearly equal. Two extra
S-units of noise is hard to overcome. I really wish the outcome had been different.
--
73, Cecil http://www.qsl.net/w5dxp



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Roy Lewallen wrote:
One thing to keep in mind is that vertically polarized waves can
propagate by ground wave, while horizontally polarized waves can't.

There are locations around my home town where the power line noise
completely blanks out WTAW, a 10KW AM station 30 miles away.
--
73, Cecil http://www.qsl.net/w5dxp



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Mark Keith wrote:
It's simple. Cecil did not use enough radials for the low height he
mounted the vertical.

I used *twice as much wire* for radials in the vertical as I used for
the entire horizontal antenna. :-) In addition, the top of the vertical
was 15 feet higher than the horizontal and was a lightning rod. In
addition, the RG-213 cost three times as much as ladder-line. Anyone
need a 33 ft aluminum tubing vertical? Come haul it away.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil, W5DXP wrote:
"I`m just reporting conditions at my QTH."

Every installation is unique, but horizontal power lines are often long
in terms of h-f waves. At a distance, one receives radiation from the
wires which tends to make a zero sum. This happens even though the h-f
is likely common-mode on the wires.

Every power pole is supposed to be grounded. Radiation induced and other
spurious currents in the power lines drains to the earth through this
multitude of earth connections. Though the phase of these currents to
earth varies in the various ground wires, you are often closer to one
than the others. Radiation phase from that particular ground wire is
usually not a jumble at a given frequency due to limited height of the
pole. Your proximity to one pole often derives from being served with
electricity from that pole.

As horizontally polarized signals don`t propagate via ground wave and
suffer extreme attenuation due to cross-polarization when sweeping
vertical wires, inducing little energy in them, and due to vertically
polarized radiation from vertical wires on power poles, vertically
polarized radiation is all you get from the poles.

For an Idea of r-f currents in the ground wire on a power pole, explore
close to the pole the signals it radiates with a transistor battery
operated portable radio. They can be intense.

Best regards, Richard Harrison, KB5WZI

One thing to keep in mind is that vertically polarized waves can
propagate by ground wave, while horizontally polarized waves can't.

Roy Lewallen, W7EL


True, but at close distances in which we have our man made noise sources, and
power lines contributing to conduct arcing, there is not that much of
"propagating" going on (almost near field). Our antennas "see" the noise
sources in their full "beauty" of "all kinds" polarization. Major factor is the
radiation pattern of the vertical (main lobe close to horizon) and its height
(lower to ground - "looking" straight at the noise sources).
Snooping with AM radio with ferite antenna can be very revealing in seeing the
polarization at particular point. Broadband noise source (spark transmitter)
can be very "ingenious" in producing and propagating the arcs over the wires
and air.

Back in Toronto I was plagued by 90% of the time with 20 over 9 from HV power
line noise. On 160 and 80 m, even from horizontals the "background" noise was
around S8. But having vertical whip stuck at the beach at Cape Hatteras, NC,
allowed me to hear rare DX at the opening and closing of the bands and getting
reports like "only or first NA station" with barefoot TX. Simply amazing. Oh,
and background noise is just non existent, S-meter needle sits at ZERO except
when static crashes.
One has to consider and select antenna systems based on requirements, geography
and noise situation. If local noise masks the signals, then fuggetabout it.
Some gadgets like noise cancellers can help in certain situations (single
source, phasing) also by positioning nulls in the antenna pattern at the noise
source can help, but it is royal pain in the butt especially for the contester.
I am willing to travel to no noise territory to enjoy hearing the band breathe.

So, saying that verticals are no good because they pick noise, is like saying
that Ferrari is no good to haul manure :-)

Yuri, K3BU, VE3BMV

Roy Lewallen wrote in message ...
Well, 50 feet of RG-58 has about 3/4 dB loss at 14 MHz. And when it's
old. . . I've got RG-58 that's well over 20 years old, and can't measure
the difference in loss between it and new cable. If it's damaged, it
might create an impedance bump, which you might or might not notice. But
that's true of larger diameter cable, too.

I'm bemused to find that today's hams have somehow gotten convinced they
all need BIG cable for a BIG signal. Maybe they've been listening to the
same ads that sell people on monster audio cables and SUVs. But I sure
hate to see this misleading concept being passed along to newcomers.
They'll fall for the ads soon enough without help.

Roy Lewallen, W7EL

I don't think I've really promoted the cause of excess loss in thin
coax, but it is worse than thick cable. By damaged, I mean waterlogged
generally. There are not too many other ways to damage it to make it
overly lossy. I've seen some old thin coax that was pretty bad as far
as loss. Quite noticable on 10m anyway...Maybe not 20m as much. I do
prefer larger coax any day of the week, but thats mainly to reduce the
losses when I have a fairly large mismatch. IE: warc band use with
tuner, etc. Also less loss on higher freq's. In this case, I only
mentioned it in case the tuner ends up not being the problem. The coax
needs to at least be considered. But I think the tuner is the likely
culprit. MK

W5DXP wrote in message ...
Mark Keith wrote:
It's simple. Cecil did not use enough radials for the low height he
mounted the vertical.

I used *twice as much wire* for radials in the vertical as I used for
the entire horizontal antenna. :-)

Unfortunately, that was not enough.

In addition, the top of the vertical
was 15 feet higher than the horizontal and was a lightning rod.

The top of mine was nearly 70 ft in the air. It was never struck once
the whole time I had it up, and went through some radical t-storms.
Funny part? After I took it down, I've had that mast struck twice,
with much less height.

In
addition, the RG-213 cost three times as much as ladder-line.

You are a retired injuneer. You should able able to afford it. :/

Anyone
need a 33 ft aluminum tubing vertical? Come haul it away.

I would, if I were closer. Then I could put up two of them, phase
them, and really kick some butt. I'd take that overpriced 213 off your
hands too. :) MK