Vertical above the ground-plane
 

I have a situation where I would like to install a vertical wire above
a fiberglass pole I have in the center of the yard. However, I must
keep the coax off the ground so I can only feed it about 7 feet from
the ground so people and the mower can get underneath. (rental
property).

I want to setup a 20 or 30 meter vertical and run ground radials from
the base of the pole where the wires can be buried. Is it possible to
feed the antenna above the ground plane? for example, I have ground
radials connected to a seven foot vertical wire, the shield side, and
the center side of the coax would continue upwards to the top, or
appropriate height on the pole.

Thanks
Buck
N4PGW

--
73 for now
Buck, N4PGW
www.lumpuckeroo.com
N4PGW

Vertical above the ground-plane
 

On Tue, 13 Mar 2007 11:15:55 -0400, Buck
wrote:

I have a situation where I would like to install a vertical wire above
a fiberglass pole I have in the center of the yard. However, I must
keep the coax off the ground so I can only feed it about 7 feet from
the ground so people and the mower can get underneath. (rental
property).

I want to setup a 20 or 30 meter vertical and run ground radials from
the base of the pole where the wires can be buried. Is it possible to
feed the antenna above the ground plane? for example, I have ground
radials connected to a seven foot vertical wire, the shield side, and
the center side of the coax would continue upwards to the top, or
appropriate height on the pole.

Thanks
Buck
N4PGW

It sounds workable but the feed impedance is pretty high.
You might match 20 meter operation with a quarter wave feeder.
You could also mount a 20 meter ground plane at 7 feet off the ground.

John Ferrell W8CCW
"Life is easier if you learn to
plow around the stumps"

Vertical above the ground-plane
 

On Tue, 13 Mar 2007 18:23:18 GMT, John Ferrell
wrote:



It sounds workable but the feed impedance is pretty high.
You might match 20 meter operation with a quarter wave feeder.
You could also mount a 20 meter ground plane at 7 feet off the ground.

John Ferrell W8CCW

I wish I could, The reason the coax con come across is that it goes
directly to the house, the radials would have to be spread out over
the common-area property. I can bury the radials, but not the coax.
The mower folk will run over it without thinking if it is on the
ground, but the radials can be carried out of the way.

Buck
n4pgw
www.lumpuckeroo.com

--
73 for now
Buck, N4PGW
www.lumpuckeroo.com
N4PGW

Vertical above the ground-plane
 

I've had a chunk of RG-213 running across my back lawn for 5 years or
so. It was laid on, but has gradually been absorbed by the grass. From day one
it has never even come close to the lawnmower blade and I keep my grass
fairly short. The same with radial wires! Consider giving it a shot.

Irv VE6BP

Buck wrote:


The mower folk will run over it without thinking if it is on the
ground, but the radials can be carried out of the way.


--
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--------------------
Irv Finkleman,
Grampa/Ex-Navy/Old Fart/Ham Radio VE6BP
Calgary, Alberta, Canada

Vertical above the ground-plane
 

Hello Buck,

If I Understand you well, one wire (7 feet) runs from the buried
radials up to 7 feet high. The coax runs 7 feet above the ground to
your shack.

Whether it is possible depends on several things. For the lower bands
(where the vertical 7 feet part is short with respect to 0.25 lambda
it will work. You need to install a very good common mode (current)
balun (several ones) to avoid common mode current into your coaxial
cable. You will have a more or less floating ground.

Least common mode problems you will have when the vertical radiator
(the part above 7 feet) is about 0.5 lambda. This high impedance will
result in low current into your vertical part of you ground system.
The disadvantage is that the impedance of the radiator is high, so you
will get a very high VSWR inside your cable (losses).

In the case where the radiator is a quarter wave, you will have an
easy match, the current in the 7 feet vertical ground wire will
radiate also.

You will get problems when your 7 feet ground wire will be in the
range of 0.2..0.3 lambda. The impedance seen from the top of the
groundwire will be high, hence the voltage at the shield of your
cable. Your common mode choke will experience high voltage (with power
dissipation as a result).

When your radiator is somewhat longer then 0.5 lambda, the current in
the ground will be opposite to the current in the main radiator,
resulting in a bad radiation pattern for DX.

Is it possible for you to create some floating ground wires?

If possible, run some more wires from the 7 feet high feedpoint to
ground. When you separate them some inches, the inductance of the 7
feet wire will reduce significantly, introducing less common mode
voltage on the cable shield. This reduces the "workload" for the
common mode choke.

Hope this will help you.


Wim
PA3DJS

Vertical above the ground-plane
 

Irv Finkleman wrote:
I've had a chunk of RG-213 running across my back lawn for 5 years or
so. It was laid on, but has gradually been absorbed by the grass. From day one
it has never even come close to the lawnmower blade and I keep my grass
fairly short. The same with radial wires! Consider giving it a shot.

Irv VE6BP

Buck wrote:


The mower folk will run over it without thinking if it is on the
ground, but the radials can be carried out of the way.

I cut a small trench with a weed eater and put my RG-8 line in that,
held in with some galvanized fence wire cut to about a foot long and
bent into a "U" shape, one "U" every three feet or so. After five years
I have a hard time finding it, let alone cutting it with the lawn mower,
give that a try!

73,
W8LNA

Vertical above the ground-plane
 

Just a silly question, did you consider the C-pole antenna ?
It could be a solution to you problem as it does NOT need any radials.
It is a much ignored antenna. I made intensive simulations with 4nec2
and the results are very interesting. The only problem is the feed
point on which you need a choking system.

73, Patrick TK5EP
http://tk5ep.fre.fr


Buck a exposé le 13/03/2007 :
I have a situation where I would like to install a vertical wire above
a fiberglass pole I have in the center of the yard. However, I must
keep the coax off the ground so I can only feed it about 7 feet from
the ground so people and the mower can get underneath. (rental
property).

I want to setup a 20 or 30 meter vertical and run ground radials from
the base of the pole where the wires can be buried. Is it possible to
feed the antenna above the ground plane? for example, I have ground
radials connected to a seven foot vertical wire, the shield side, and
the center side of the coax would continue upwards to the top, or
appropriate height on the pole.

Thanks
Buck
N4PGW

Vertical above the ground-plane
 

I hear that RG-8 shouldn't be buried, but if not, the reason for the
problem is the hired help with the mower people. They either will
chop it up or won't cut near it and complain to the land lord. He
hasn't complained about what we have so far, so I am keeping it low
key until we can find a better, ham-friendly place in which to move.

Thank you,
Buck
N4pgw


On Tue, 13 Mar 2007 19:44:02 GMT, Irv Finkleman
wrote:

I've had a chunk of RG-213 running across my back lawn for 5 years or
so. It was laid on, but has gradually been absorbed by the grass. From day one
it has never even come close to the lawnmower blade and I keep my grass
fairly short. The same with radial wires! Consider giving it a shot.

Irv VE6BP

Buck wrote:


The mower folk will run over it without thinking if it is on the
ground, but the radials can be carried out of the way.


--
73 for now
Buck, N4PGW
www.lumpuckeroo.com
N4PGW

Vertical above the ground-plane
 

"Buck" wrote in message
...
I hear that RG-8 shouldn't be buried, but if not, the reason for the
problem is the hired help with the mower people. They either will
chop it up or won't cut near it and complain to the land lord. He
hasn't complained about what we have so far, so I am keeping it low
key until we can find a better, ham-friendly place in which to move.

Thank you,
Buck
N4pgw


On Tue, 13 Mar 2007 19:44:02 GMT, Irv Finkleman
wrote:

I've had a chunk of RG-213 running across my back lawn for 5 years or
so. It was laid on, but has gradually been absorbed by the grass. From
day one
it has never even come close to the lawnmower blade and I keep my grass
fairly short. The same with radial wires! Consider giving it a shot.

Irv VE6BP

Buck wrote:


The mower folk will run over it without thinking if it is on the
ground, but the radials can be carried out of the way.


--
73 for now
Buck, N4PGW

Hi Buck

Are you interested in experimenting? I would have tried something like
this ----

Run the RG-8 from the "building" to the monopole parallel to the ground
and 7 feet above it. Drop it down parallel to the monopole a few inches
from it all the way to the ground. At the ground, connect the coax the
same way a conventional monopole is connected.

Any low loss, high dielectric constant, material in the immediate vicinity
of the parallel coax and monopole will help. A coiled coax type "balun"
at the antenna end of the horizontal coax will really be needed too.

I have no idea if you want to "play" with antenna ideas. And, I have no
certainty that the antenna would work anyway.

Jerry

Vertical above the ground-plane
 

On Wed, 14 Mar 2007 16:42:23 GMT, "Jerry Martes"
wrote:


"Buck" wrote in message
.. .
I hear that RG-8 shouldn't be buried, but if not, the reason for the
problem is the hired help with the mower people. They either will
chop it up or won't cut near it and complain to the land lord. He
hasn't complained about what we have so far, so I am keeping it low
key until we can find a better, ham-friendly place in which to move.

Thank you,
Buck
N4pgw


On Tue, 13 Mar 2007 19:44:02 GMT, Irv Finkleman
wrote:

I've had a chunk of RG-213 running across my back lawn for 5 years or
so. It was laid on, but has gradually been absorbed by the grass. From
day one
it has never even come close to the lawnmower blade and I keep my grass
fairly short. The same with radial wires! Consider giving it a shot.

Irv VE6BP

Buck wrote:


The mower folk will run over it without thinking if it is on the
ground, but the radials can be carried out of the way.


--
73 for now
Buck, N4PGW

Hi Buck

Are you interested in experimenting? I would have tried something like
this ----

Run the RG-8 from the "building" to the monopole parallel to the ground
and 7 feet above it. Drop it down parallel to the monopole a few inches
from it all the way to the ground. At the ground, connect the coax the
same way a conventional monopole is connected.

Any low loss, high dielectric constant, material in the immediate vicinity
of the parallel coax and monopole will help. A coiled coax type "balun"
at the antenna end of the horizontal coax will really be needed too.

I have no idea if you want to "play" with antenna ideas. And, I have no
certainty that the antenna would work anyway.

Jerry

That is definitely an idea to consider. I will have about four to six
inches it'll be away from the vertical.

Buck
n4pgw

--
73 for now
Buck, N4PGW
www.lumpuckeroo.com
N4PGW