Not to be confused with the company bearing the name (Shakespeare) and
having made, or is making, chicken band antennas...

John

"John Smith" wrote in message
...
Walter:

Does that mean you do agree with me and Shakespeare sucks--or not?
grin

John

"Walter Maxwell" wrote in message
...

"Richard Clark" wrote in message
news
On Tue, 21 Jun 2005 21:34:32 -0400, "Walter Maxwell"
wrote:

Lying slander is a redundancy, isn't it?

Hi Walt,

The laws, and I imagine the understanding, varies immensely across
all
borders and jurisdictions. In some places it is slander to reveal
the
truth, in others to disparage with a lie.

One could imagine the paradox of uttering a lying truth, I suppose.
However, given Reg's propensity to slander outrageously, as though
it
were a prerogative of old age and infirmity, and to wrap me in under
the same mantle well before my time (but perhaps not infirmity);
this
callow youth takes it as no less honour than the tap of the sword on
the shoulders by a Queen.

Alternately, lacking any quantitative data, a shortfall that Sir
Kelvinator of ice box fame would shudder at, I cannot think Reg's
opprobrium is any less part of the act of Punchinello (in other
words,
indistinguishable from honest labor when such is so mixed with
intemperance and reckless fulmination).

Either way, I always enjoy the flourish of his hyperbolic arcs.

73's
Richard Clark, KB7QHC

Richard, as I both said and implied earlier, I enjoy you both
immensely. Your elegant usage of expression as a degreed literary is
hardly unnoticeable.

Walt

Roy, W7EL wrote:
"What conclusions could we draw from that information?"

My comment is a little off topic as it is not about measuring soil
constants. It is only an opinion that the FCC`s decisions regarding a
standard grounding system for medium wave broadcast stations worked out
very well. 120 redials each about 1/4-wavelength seems to work well
whether soil is good or bad.

In summer or winter, if the ground cracks open from drought or is
covered with a foot or more of floodwater, the tower currents and field
strengths hardly change at all. Directional patterns are unaffected.
Amazing and well done!

Best regards, Richard Harrison, KB5WZI

"Fred W4JLE" wrote
Reg;
How many radials are required in GB for a commercial broadcast
station ?


====================================
Fred,
Depends on how long and thick they are. But in general, just
sufficient to meet overall technical and economic requirements with
one or two more for luck.

Design engineers, just to be awkward, are inclined to deliberately
avoid 120. Then they can sit back and have a good laugh when it still
works.
----
Reg, G4FGQ

I forgot to say all measurements were made in or near the domestic
kitchen sink.
----
Reg.

Reg, G4FGQ wrote:
"A typical American way of going apoutthings.) "

Later to be called "Shock and Awe"?

Best regards, Richard Harrison, KB5WZI

Earlier I said a volume of soil between electrodes behaves as a
capacitor in parallel with a resistance.

To conform better to the impedance-frequency response of real soil, a
better simulation is obtained with another resistor in series with the
capacitor. Better still add a 3rd resistor in series with a second
capacitor, both in shunt with R1, C1 and R2.

I have a computer program somewhere which assists in designing a
circuit to simulate a given type of soil. But what use such circuits
might have is a matter for conjecture.

It is more convenient and practical to work in terms of resistance
rather than the scientific term conductivity. Ohm-metres rather than
milli-Siemens. When thinking in terms of conductivity I always feel I
should be standing on my head.

The resistance measured between opposite faces of a 1-metre cube of
the soil is 1000 ohms when the soil has a resistivity of 1000
ohm-meters.

A poor soil is 1000 ohms = 1 milli-S Sea water is 0.22 ohms.

One can visualise a 1 metre cube of the material. The permittivity of
the material being the nunber of times the measured capacitance
exceeds the calculated capacitance between the electrodes when only
air is present. It's about 9 pF.
----
Reg, G4FGQ

Roy Lewallen wrote:

But under no circumstances should you actually stoop to reading the
paper you're so fond of criticizing.

Are BLE's original papers available on the web? If not, that does
represent a substantial problem.

Despite having several derivative references, I must admit to never
having seen the originals either. But I do have enough information to
judge BLE's work worthy of respect. Pioneers always deserve an extra
helping of respect because - unlike everyone else, including all their
critics - they didn't have the benefit of perfect hindsight.

On the other hand, that work was done almost three-quarters of a century
ago. If we don't know more than the pioneers did, then we have wasted
their efforts.


--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Richard Harrison wrote:
Roy, W7EL wrote:
"What conclusions could we draw from that information?"

My comment is a little off topic as it is not about measuring soil
constants. It is only an opinion that the FCC`s decisions regarding a
standard grounding system for medium wave broadcast stations worked out
very well. 120 redials each about 1/4-wavelength seems to work well
whether soil is good or bad.

In summer or winter, if the ground cracks open from drought or is
covered with a foot or more of floodwater, the tower currents and field
strengths hardly change at all. Directional patterns are unaffected.
Amazing and well done!

Well, not exactly amazing, since the FCC deliberately requires the
ground to be covered by so many radials that the location and its ground
conditions don't matter any more.

That was an administrative policy decision rather than a technical one.
From the technical viewpoint, everybody agrees that 120*0.25wl is more
than enough to override the local ground conditions under the tower
irrelevant.

The real technical question is: how many, and how long, will be "just
enough" for "here"? That obviously requires a lot more knowledge and
engineering judgement.

Having just taken delivery of two miles of radial wire, the question of
"How much is enough?" is starting to become very practical...


--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Ian White GM3SEK wrote:

. . .
The real technical question is: how many, and how long, will be "just
enough" for "here"? That obviously requires a lot more knowledge and
engineering judgement.
. . .

And for the purpose at hand. We have to keep in mind that the
requirements for AM broadcasters are quite different from those of
amateurs. A few percent difference in field strength means a few percent
difference in a broadcaster's audience size and therefore in advertising
income. This income difference is felt year after year, so any change
that brings a few percent increase in field strength is worth a fair
amount of money for a broadcaster to implement. On the other hand, a
difference of 1 dB (more than a 20% change in efficiency or 10% change
in field strength) is seldom worthwhile at all for most amateurs.

I'm not sure why the great hangup on how many radials AM broadcasters
use. It certainly isn't what most amateurs need.

Roy Lewallen, W7EL

"Roy Lewallen" wrote in message
...
Ian White GM3SEK wrote:

. . .
The real technical question is: how many, and how long, will be "just enough"
for "here"? That obviously requires a lot more knowledge and engineering
judgement.
. . .
Well, Ian, the BLE paper reports data allowing one to make that engineering
judgement. It's unfortunate that my copy of the paper is in my library in
Florida, and I won't be back there until November to scan it for the group.
However, I have ordered a copy from the Michigan State U library.

The BLE experiments were conducted to determine what combination of radials
would form the best simulation of a perfect ground, i.e., what combination would
achieve a field strength closest to the ideal calculated value. One factor they
considered is that when the spacing between adjacent wires in a grid structure
is 1/20 lambda or less, the effect is that of a continuous reflecting surface.
The spacing between radials is not exactly the same as a grid structure, but the
effect is similar.

BLE found that the optimum length of the radials in the ground is not related to
resonant length as it is with elevated radials. They found that the principal
reason for the optimum length concerns the volume containing the significant
energy in the electromagnetic fields in the space surrounding the radiator that
intersects the ground. They found that at a distance of 0.4 lambda from the
radiator the energy in the fields has reduced to the level of diminishing
returns, where collecting the currents at a greater distance would yield no
significant decrease in loss resistance, and therefore no further increase in
field strength. Indeed, the field strength obtained with at least 90 radials 0.4
lambda in length was found to be insignificantly less than that of a perfect
ground. This fact was unknown prior to BLE's experiments. I can't remember the
exact difference shown in the graph, but it is inconsequential.

With the radials simulating a near-perfect reflecting ground plane the skin
depth of the earth beneath the radials is of no consequence, because the RF
energy is nearly totally reflected, with only an insignificant amount
transmitted through the ground plane. Consequently, the soil conditions directly
beneath the ground plane are irrevelant.

However, the soil conditions immediately external to the ground plane are
important to the intensity of the ground wave propagation from vertical
radiators. The poorer the soil conductivity the greater the loss at low angles
of elevation. And as we all know, propagation of the ground wave is frequency
sensitive. Many years ago, using the FCC propagation charts of field strength vs
distance for a conductivity of 8, the geographical area covered with a field
strenght of 1 mv/meter at 1 mile for a 250 watt station at 550 KHz would require
47 kilowatts at 1500 KHz to cover the same area with the same signal level.

When I receive the requested copy of the BLE paper I'll scan it and publish it
for all to see.

Walt, W2DU