On 30/11/2015 18:34, wrote:
In rec.radio.amateur.antenna Spike wrote:

Imagine a case whereby someone digs up the soil around the base of a
vertical antenna, a couple of feet deep and as far out as the antenna is
tall. Into this they mix 2 percent of high-aspect-ratio thin conducting
fibres, say about a foot long, and then replace the soil. 2 percent of
conducting fibres in an essentially non-conducting medium is about the
minimum proportion necessary to reach the percolation threshold..

What results from your modelling exercise do you get in this case?

Modeling thing buried in the soil requires professional software that
costs on the order of $1,000.

To do this with reasonably priced (for a hobby) software requires that
effective soil conductivity be determined.

Send me either $1,000.00 or the effective soil conductivity and I'll
be glad to do it.

The effective soil conductivity will be close to the fully conductive
value of the fibres - that's what percolation does. The high aspect
ratio fibres are a method of achieving that in a poorly conductive
medium such as soil.


--
Spike

"Crime butchers innocence to secure a throne, and innocence struggles
with all its might against the attempts of crime"

- Maximilien Robespierre

In rec.radio.amateur.antenna Spike wrote:
On 30/11/2015 18:34, wrote:
In rec.radio.amateur.antenna Spike wrote:

Imagine a case whereby someone digs up the soil around the base of a
vertical antenna, a couple of feet deep and as far out as the antenna is
tall. Into this they mix 2 percent of high-aspect-ratio thin conducting
fibres, say about a foot long, and then replace the soil. 2 percent of
conducting fibres in an essentially non-conducting medium is about the
minimum proportion necessary to reach the percolation threshold..

What results from your modelling exercise do you get in this case?

Modeling thing buried in the soil requires professional software that
costs on the order of $1,000.

To do this with reasonably priced (for a hobby) software requires that
effective soil conductivity be determined.

Send me either $1,000.00 or the effective soil conductivity and I'll
be glad to do it.

The effective soil conductivity will be close to the fully conductive
value of the fibres - that's what percolation does. The high aspect
ratio fibres are a method of achieving that in a poorly conductive
medium such as soil.

One can not enter text into a model; numbers please.


--
Jim Pennino

On 30/11/2015 23:53, wrote:
In rec.radio.amateur.antenna Spike wrote:

The effective soil conductivity will be close to the fully conductive
value of the fibres - that's what percolation does. The high aspect
ratio fibres are a method of achieving that in a poorly conductive
medium such as soil.

One can not enter text into a model; numbers please.

Much of this has already been done, 'this' meaning studying the effects
of ground conductivity and number of radials (going up to 64) by N6LF in
QEX with the latest version being published in September/October this year.

Note for Brian Howie: the study encompasses 472 kHz, and it should be
noted that below 1MHz the soil electromagnetic parameters diverge
significantly from HF values. This implies that a different approach is
needed, and one of the articles looks at this - you might find this of
interest.


--
Spike

"Crime butchers innocence to secure a throne, and innocence struggles
with all its might against the attempts of crime"

- Maximilien Robespierre

In message , Spike
writes
On 30/11/2015 23:53, wrote:
In rec.radio.amateur.antenna Spike wrote:

The effective soil conductivity will be close to the fully conductive
value of the fibres - that's what percolation does. The high aspect
ratio fibres are a method of achieving that in a poorly conductive
medium such as soil.

One can not enter text into a model; numbers please.

Much of this has already been done, 'this' meaning studying the effects
of ground conductivity and number of radials (going up to 64) by N6LF
in QEX with the latest version being published in September/October
this year.

Note for Brian Howie: the study encompasses 472 kHz, and it should be
noted that below 1MHz the soil electromagnetic parameters diverge
significantly from HF values. This implies that a different approach is
needed, and one of the articles looks at this - you might find this of
interest.

Thanks I've had a look at them . If I ever get round to transmitting
there, I'll need a lot of earth.

I'm still using my 5 foot loop for receive, but it's now series tuned,
rather than parallel with a coupling loop and seems to work a bit
better.

By coincidence my morning training run took me near the EDN NDB

http://www.b-howie.demon.co.uk/lfbcon.htm

It's a top loaded vertical, but looking over the fence, I could see a
lot green earth wire radials on the surface. It's possible there are
buried ones too , but there are only about 6 and they can't be more than
15ft long,

Brian
--
Brian Howie

On 03/12/2015 12:45, Brian Howie wrote:
In message , Spike
writes

Note for Brian Howie: the study encompasses 472 kHz, and it should be
noted that below 1MHz the soil electromagnetic parameters diverge
significantly from HF values. This implies that a different approach
is needed, and one of the articles looks at this - you might find
this of interest.

Thanks I've had a look at them . If I ever get round to transmitting
there, I'll need a lot of earth.

I guess it will need a lot of planning! And wire...

I'm still using my 5 foot loop for receive, but it's now series tuned,
rather than parallel with a coupling loop and seems to work a bit better.

Do you find the S/N is improved with a loop? Have you thought of trying
a shielded loop?

By coincidence my morning training run took me near the EDN NDB

http://www.b-howie.demon.co.uk/lfbcon.htm

It's a top loaded vertical, but looking over the fence, I could see a
lot green earth wire radials on the surface. It's possible there are
buried ones too , but there are only about 6 and they can't be more than
15ft long,

For the beacon to be of maximum use, they'll need a good sky-wave
signal; it sounds like the visible radials are there to provide a DC
path to earth probably in association with a ground spike, rather than
for getting the main lobe lowered.


--
Spike

"Crime butchers innocence to secure a throne, and innocence struggles
with all its might against the attempts of crime"

- Maximilien Robespierre

In rec.radio.amateur.antenna Spike wrote:
On 03/12/2015 12:45, Brian Howie wrote:
In message , Spike
writes

Note for Brian Howie: the study encompasses 472 kHz, and it should be
noted that below 1MHz the soil electromagnetic parameters diverge
significantly from HF values. This implies that a different approach
is needed, and one of the articles looks at this - you might find
this of interest.

Thanks I've had a look at them . If I ever get round to transmitting
there, I'll need a lot of earth.

I guess it will need a lot of planning! And wire...

I'm still using my 5 foot loop for receive, but it's now series tuned,
rather than parallel with a coupling loop and seems to work a bit better.

Do you find the S/N is improved with a loop? Have you thought of trying
a shielded loop?

By coincidence my morning training run took me near the EDN NDB

http://www.b-howie.demon.co.uk/lfbcon.htm

It's a top loaded vertical, but looking over the fence, I could see a
lot green earth wire radials on the surface. It's possible there are
buried ones too , but there are only about 6 and they can't be more than
15ft long,

For the beacon to be of maximum use, they'll need a good sky-wave
signal; it sounds like the visible radials are there to provide a DC
path to earth probably in association with a ground spike, rather than
for getting the main lobe lowered.

Sky wave propagation doesn't happen at those frequencies for all practical
purposes.

Sky wave propagation was discovered when amateurs started using frequencies
greater than 200 meters.



--
Jim Pennino

On 05/12/2015 03:40, wrote:
In rec.radio.amateur.antenna Spike wrote:
On 03/12/2015 12:45, Brian Howie wrote:

By coincidence my morning training run took me near the EDN NDB

http://www.b-howie.demon.co.uk/lfbcon.htm

It's a top loaded vertical, but looking over the fence, I could see a
lot green earth wire radials on the surface. It's possible there are
buried ones too , but there are only about 6 and they can't be more than
15ft long,

For the beacon to be of maximum use, they'll need a good sky-wave
signal; it sounds like the visible radials are there to provide a DC
path to earth probably in association with a ground spike, rather than
for getting the main lobe lowered.

Sky wave propagation doesn't happen at those frequencies for all practical
purposes.

That's amazing. So all those aircraft at 35000 feet in its service area
can't hear the beacon? If it didn't have sky wave, it would merely be a
ground-wave beacon, not much use as there aren't that many airports
within 35 miles of Edinburgh, and the aircraft captains would know where
they were anyway.

Sky wave propagation was discovered when amateurs started using frequencies
greater than 200 meters.

What's interesting here is now much of the radiated power goes
sky-wards, and how much goes into surface wave. But apparently no-one's
ever thought to determine this, so it'll remain a mystery.


--
Spike

"Crime butchers innocence to secure a throne, and innocence struggles
with all its might against the attempts of crime"

- Maximilien Robespierre