I want to put up a "long wire" with the feedpoint at one of the back end
corners of the garden. I need a good RF ground.

If I got a length of 6 foot wide copper sheet and made out of it a cylinder,
say 6 feet in diameter, and then placed that cylinder in an upwards position
in the ground, the top level with the surface, would that be a good idea for
trying to acheive a decent RF ground? Also, is there anything I could place
around the cylinder to better the conduction between the cyinder and the
earth around it? Should I drill holes in the cylinder so I can pour water
into the cylinder to keep the ground around it moist?

Would I still benefit from some radials in the ground?

My garden's about 33 foot long, 21 foot wide. Ground gets rather rocky and a
bit sandyish at about 9 inches or so from the surface.TIA.

Richard wrote:
I want to put up a "long wire" with the feedpoint at one of the back end
corners of the garden. I need a good RF ground.

If I got a length of 6 foot wide copper sheet and made out of it a
cylinder,
say 6 feet in diameter, and then placed that cylinder in an upwards
position
in the ground, the top level with the surface, would that be a good idea
for
trying to acheive a decent RF ground? Also, is there anything I could place
around the cylinder to better the conduction between the cyinder and the
earth around it? Should I drill holes in the cylinder so I can pour water
into the cylinder to keep the ground around it moist?

Would I still benefit from some radials in the ground?

My garden's about 33 foot long, 21 foot wide. Ground gets rather rocky
and a bit sandyish at about 9 inches or so from the surface.TIA.

That might be overkill.. Why not spend the money on a spool of copper
wire and lay radials. For RF purposes, large area of coverage is more
important than low impedance at a particular point. You want to improve
the apparent conductivity of the soil over as much volume as you can.
Think of your grounding system as (partially) a big leaky capacitor to
"the earth".. you want to spread the RF current out over as large an
area as possible, and radials are probably the easiest way to do it.
There's nothing special about how you lay the radials or their length
(they're in dirt, so they're not tuned or resonant.. just wires).

On Thu, 19 Apr 2007 17:55:03 +0100, "Richard"
wrote:

If I got a length of 6 foot wide copper sheet and made out of it a cylinder,
say 6 feet in diameter, and then placed that cylinder in an upwards position
in the ground, the top level with the surface, would that be a good idea for
trying to acheive a decent RF ground?

Hi Richard,

Not particularly.

Also, is there anything I could place
around the cylinder to better the conduction between the cyinder and the
earth around it?

You could slit the cylinder lengthwise and lay it on or beneath the
soil.

Should I drill holes in the cylinder so I can pour water
into the cylinder to keep the ground around it moist?

This a bromide from the late 20s and 30s. Yes, it would keep the
ground moist, encourage moss, and increase the density of earthworms.

Would I still benefit from some radials in the ground?

Always, first, and foremost.

My garden's about 33 foot long, 21 foot wide. Ground gets rather rocky and a
bit sandyish at about 9 inches or so from the surface.TIA.

Lay out a fan of radials as far as you can go. Make it about a dozen
to sixteen. Move on because there is small chance of significant
improvement beyond that.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Thu, 19 Apr 2007 17:55:03 +0100, "Richard"
wrote:

If I got a length of 6 foot wide copper sheet and made out of it a
cylinder,
say 6 feet in diameter, and then placed that cylinder in an upwards
position
in the ground, the top level with the surface, would that be a good idea
for
trying to acheive a decent RF ground?

Hi Richard,

Not particularly.

Also, is there anything I could place
around the cylinder to better the conduction between the cyinder and the
earth around it?

You could slit the cylinder lengthwise and lay it on or beneath the
soil.

Should I drill holes in the cylinder so I can pour water
into the cylinder to keep the ground around it moist?

This a bromide from the late 20s and 30s. Yes, it would keep the
ground moist, encourage moss, and increase the density of earthworms.

Would I still benefit from some radials in the ground?

Always, first, and foremost.

My garden's about 33 foot long, 21 foot wide. Ground gets rather rocky and
a
bit sandyish at about 9 inches or so from the surface.TIA.

Lay out a fan of radials as far as you can go. Make it about a dozen
to sixteen. Move on because there is small chance of significant
improvement beyond that.

73's
Richard Clark, KB7QHC

Good 60Hs ground doesnt mean its a good RF ground. The casing of an
abandoned well gives me about a 4 ohm 60 hz ground but about 25 ohms ground
on 20 meters.

Jimmie

"Jim Lux" wrote in message
...
Richard wrote:
I want to put up a "long wire" with the feedpoint at one of the back end
corners of the garden. I need a good RF ground.

If I got a length of 6 foot wide copper sheet and made out of it a
cylinder,
say 6 feet in diameter, and then placed that cylinder in an upwards
position
in the ground, the top level with the surface, would that be a good idea
for
trying to acheive a decent RF ground? Also, is there anything I could
place
around the cylinder to better the conduction between the cyinder and the
earth around it? Should I drill holes in the cylinder so I can pour water
into the cylinder to keep the ground around it moist?

Would I still benefit from some radials in the ground?

My garden's about 33 foot long, 21 foot wide. Ground gets rather rocky
and a bit sandyish at about 9 inches or so from the surface.TIA.

That might be overkill.. Why not spend the money on a spool of copper
wire and lay radials. For RF purposes, large area of coverage is more
important than low impedance at a particular point. You want to improve
the apparent conductivity of the soil over as much volume as you can.
Think of your grounding system as (partially) a big leaky capacitor to
"the earth".. you want to spread the RF current out over as large an area
as possible, and radials are probably the easiest way to do it. There's
nothing special about how you lay the radials or their length (they're in
dirt, so they're not tuned or resonant.. just wires).

Maybe a 3 foot wde cylinder would be adequate.

One thing: Why are radials so effective? They are not resonant
counterpoises, and from the aspect of surface area in contact with ground,
radials have hardly any surface area that "connects" with "the earth". I can
understand if I put in a 20 foot by 20 foot copper plate flat in the earth
that would "connect" to earth quite well, I mean the measured ohmic
resistance to "the earth" could be quite low. But also capacitive coupling
would be low too. But radials have no real capacitive coupling to "the
earth" neither much surface area in contact with "the earth". So it confuses
me as to why they are so effective.

BTW, since it looks like many wires in the earth are as good as a plate,
perhaps I could put in a wire mesh grid about 1 foot under the soil over the
whole garden . I'm digging up the garden anyway. Perhaps with some ground
stakes here and there connected to the grid, although maybe not necessary.

"Richard" wrote in message
...

I said:

Maybe a 3 foot wde cylinder would be adequate.

One thing: Why are radials so effective? They are not resonant
counterpoises, and from the aspect of surface area in contact with ground,
radials have hardly any surface area that "connects" with "the earth". I
can understand if I put in a 20 foot by 20 foot copper plate flat in the
earth that would "connect" to earth quite well, I mean the measured ohmic
resistance to "the earth" could be quite low. But also capacitive coupling
would be low too. But radials have no real capacitive coupling to "the
earth" neither much surface area in contact with "the earth". So it
confuses me as to why they are so effective.

BTW, since it looks like many wires in the earth are as good as a plate,
perhaps I could put in a wire mesh grid about 1 foot under the soil over
the whole garden . I'm digging up the garden anyway. Perhaps with some
ground stakes here and there connected to the grid, although maybe not
necessary.

The only thing that I can think of why radials are effective is nothing to
do with ohmic resistance to "the earth" or capactive coupling to "the
earth". Not even to do with a large surface area in contact with the ground.
It's simply that the ground is changed, those radials simply make "the
earth" in that locality less like an insulator and more like a conductor.
More like the radials make the ground below your feet more like say
a pool of salt water than the high resistivity ground that it normally is.
What do you think?

On Fri, 20 Apr 2007 07:58:16 +0100, "Richard"
wrote:

More like the radials make the ground below your feet more like say
a pool of salt water than the high resistivity ground that it normally is.
What do you think?

Hi Richard,

Actually salt water sucks as a local ground - it is as poor a "good"
conductor as you could imagine. Carbon is a far better conductor than
salt water, but no one yet has suggested building on top of a coal
seam.

You would be better off filling your yard with sand to the depth of 30
feet or so (yeah, sure). The testimonials attributed to salt water
comes with its far field qualities of a tremendous mismatch to air and
offering spectacularly low radiation launch angles.

So, copper replaces a very poor conductor (as a first pass
approximation). Invest your copper in close proximity to the base of
the antenna. That is, a lot of short radials, and a fair number of
medium size ones, and a few long ones.

Two things to consider. The ground closest to the antenna is
responsible for efficiency in loading. The ground further out
(between 5 and 10 wavelengths, or more) is responsible for launch
efficiency (offering lower launch angles).

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
On Fri, 20 Apr 2007 07:58:16 +0100, "Richard"
wrote:

More like the radials make the ground below your feet more like say
a pool of salt water than the high resistivity ground that it normally is.
What do you think?

Hi Richard,

Actually salt water sucks as a local ground - it is as poor a "good"
conductor as you could imagine. Carbon is a far better conductor than
salt water, but no one yet has suggested building on top of a coal
seam.

You would be better off filling your yard with sand to the depth of 30
feet or so (yeah, sure). The testimonials attributed to salt water
comes with its far field qualities of a tremendous mismatch to air and
offering spectacularly low radiation launch angles.

So, copper replaces a very poor conductor (as a first pass
approximation). Invest your copper in close proximity to the base of
the antenna. That is, a lot of short radials, and a fair number of
medium size ones, and a few long ones.

Two things to consider. The ground closest to the antenna is
responsible for efficiency in loading. The ground further out
(between 5 and 10 wavelengths, or more) is responsible for launch
efficiency (offering lower launch angles).

Hmm, a new concept introduced.

I was thinking on these lines.

The first thing to do is to prepare the ground, that is, alter the nature of
the ground in the vicinity of the antenna from an electrical point of view.
To improve from "poor ground" to "good ground", in an electrical sense. That
can be done by laying wires in the ground (radials) or a wire mesh. Once
that is done, one is in a better postion to have the best RF ground
possible. I think this is what the radial/wires do, they simply alter the
nature of the ground where they are placed. This is like making poor ground,
good ground or good ground, excellent ground by laying wires in the ground.

Now what seems to be the case is that there is an advantage in making the
ground nearest the antenna the very best ground that you can. So, if you are
going to use wires to better the ground, make sure that most radials go in
near the base of the antenna.

Of course, wires improve the ground, it's conductivity, but in practice, you
tend to connect the antenna to the radials/wires rather than make for
seperate arrangements.

On Thu, 19 Apr 2007 17:55:03 +0100, "Richard"
wrote:

I want to put up a "long wire" with the feedpoint at one of the back end
corners of the garden. I need a good RF ground.

If I got a length of 6 foot wide copper sheet and made out of it a cylinder,
say 6 feet in diameter, and then placed that cylinder in an upwards position
in the ground, the top level with the surface, would that be a good idea for
trying to acheive a decent RF ground? Also, is there anything I could place
around the cylinder to better the conduction between the cyinder and the
earth around it? Should I drill holes in the cylinder so I can pour water
into the cylinder to keep the ground around it moist?

Would I still benefit from some radials in the ground?

My garden's about 33 foot long, 21 foot wide. Ground gets rather rocky and a
bit sandyish at about 9 inches or so from the surface.TIA.

Check out http://www.bencher.com/pdfs/00361ZZV.pdf
and http://www.bencher.com/pdfs/00803ZZV.pdf

We usually associate an RF ground with verticals. I believe what you
are referring to as a "long wire" is usually called an :inverted L".

I think your proposed depth of 1 foot or more may be too deep for best
performance.

If you are planning cultivate your garden on a regular basis and use
it for a radial field you have some unique problems. Insulated wire on
top of the ground works as well as buried bare wire.

The consensus seems to be that each time you double your number of
radials you gain a db up to about 128 of them. essentially, more is
better. Popular thinking is that 16 are the minimum.

I experimented with using electrical extension cords of various length
for a radial system and found that all efforts would work but more is
always better! One radial will get you on the air but just barely! I
suspect a quarter wave radiator in any configuration and 4 radials
would beat any mobile installation.

If I were you I would invest in a few orange extension cords and run
them on top of the ground IN the garden rows. Orange will be easy to
see and avoid when you cultivate your garden. They will be easy to
remove and re deploy for garden cleanup.
Plan on assuring the curious neighbors that you are electrically
stimulating your garden. That will probably subdue any objections.

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

On Fri, 20 Apr 2007 09:02:34 +0100, "Richard"
wrote:

The first thing to do is to prepare the ground, that is, alter the nature of
the ground in the vicinity of the antenna from an electrical point of view.
To improve from "poor ground" to "good ground", in an electrical sense. That
can be done by laying wires in the ground (radials) or a wire mesh. Once
that is done, one is in a better postion to have the best RF ground
possible. I think this is what the radial/wires do, they simply alter the
nature of the ground where they are placed. This is like making poor ground,
good ground or good ground, excellent ground by laying wires in the ground.

Hi Richard,

Yes, this is a good analogy. It fails quickly, however. That is, you
do not gain better ground characteristics in proportion to the number
of radials.

So, as general rules go, the common advice is to make your radials as
long as the radiator is high, and to lay out as many as you feel
comfortable doing. If you need a hard number, then a dozen to sixteen
is a good starting place from which others can argue ceaselessly to
offer you to gain only 1 more dB of performance (maybe 2).

Now what seems to be the case is that there is an advantage in making the
ground nearest the antenna the very best ground that you can. So, if you are
going to use wires to better the ground, make sure that most radials go in
near the base of the antenna.

Of course, wires improve the ground, it's conductivity, but in practice, you
tend to connect the antenna to the radials/wires rather than make for
seperate arrangements.

True, that is the sense of a counterpoise. However, even a ground
field beneath a dipole overhead improves the dipole's performance and
there is no direct connection there. Some would argue this only
describes a yagi pointing straight up and the gain only comes to more
power poured into the clouds. Yes, this is an appealing argument, and
yet if you consider how much the gain rises at a low angle of launch;
then you find it is beneficial in that respect as well.

The alternative view of radials is that they operate as a shield
against loss.

73's
Richard Clark, KB7QHC