Has it taken 70 years for the old wives of the FCC to return to Earth,
disregarding B.L & E who forgot to measure ground conductivity, not to
mention permittivity, and think again about economics?

The only stations that the FCC is concerned about is commercial.
And the reason they stick with the standard number is for stability
and getting the max bang for buck, and an easily expected
performance level. Buying a load of wire will beat using more
transmitter power over the long run. If they use 120 radials,
they know they will be getting close to maximum performance.
If they don't, it's a crap shoot. 120 radials *will* outperform
16 of them. There is no question, unless they are over sea
water. I'm not saying hams have to run that many. In fact, I
think 60 will do for most, except the most hard core for good
results. Even less for the more casual user.
But I have no problems with the FCC wanting a certain level
of performance for commercial stations. I have no problems
seeing why they do it either. Wire is cheap compared to
todays level of monthly light bill. With some stations, the radials,
or lack of , in certain directions gives them a controlable
pattern with no surprises in f/s over a period of time
with changing ground conditions. The main thing is
stability of performance over periods of time. Or thats
my take anyway.
MK

All,

A fundamental basic question, which is the primary purpose of radials:

1. is it to create a ground, that is a as close as possible to zero ohm virtual
reference for the 'real' vertical half of the dipole?

2. Or are they to create a real resonant half of a dipole?

If it is the first then what does the 'efficiency' curve look like for a
shortened, loaded, vertical? That is if the vertical element is loaded to
resonate at 1/5 of a half wave length what does the ground resistance profile
look like for 120 radials at various lengths of 1/20 wave, 1/10 wave and 1/5 wave?

The question I am really driving at is if mesh is layed down at 100% coverage
about what fraction of a wave length needs to be covered to create a 2.5, 5, and
10 ohm equivalent ground for the vertical above?

In the paragraph above is the mesh simulating a ground or is it fact operating
as a ground.

Thanks,
Dan

wrote:
Has it taken 70 years for the old wives of the FCC to return to Earth,
disregarding B.L & E who forgot to measure ground conductivity, not to
mention permittivity, and think again about economics?

The only stations that the FCC is concerned about is commercial.
And the reason they stick with the standard number is for stability
and getting the max bang for buck, and an easily expected
performance level. Buying a load of wire will beat using more
transmitter power over the long run. If they use 120 radials,
they know they will be getting close to maximum performance.
If they don't, it's a crap shoot. 120 radials *will* outperform
16 of them. There is no question, unless they are over sea
water. I'm not saying hams have to run that many. In fact, I
think 60 will do for most, except the most hard core for good
results. Even less for the more casual user.
But I have no problems with the FCC wanting a certain level
of performance for commercial stations. I have no problems
seeing why they do it either. Wire is cheap compared to
todays level of monthly light bill. With some stations, the radials,
or lack of , in certain directions gives them a controlable
pattern with no surprises in f/s over a period of time
with changing ground conditions. The main thing is
stability of performance over periods of time. Or thats
my take anyway.
MK

dansawyeror wrote:
All,

A fundamental basic question, which is the primary purpose of radials:

1. is it to create a ground, that is a as close as possible to zero ohm
virtual reference for the 'real' vertical half of the dipole?

There is no such thing as "creating a ground". As for a "virtual
reference", you can declare any point on any conductor a "reference" and
for that matter "ground" that you wish.

2. Or are they to create a real resonant half of a dipole?

There's no need to try to make a dipole. If the radials are on or very
near the ground, their sole purpose is to reduce the amount of loss due
to current returning to the base of the antenna. The current entering
the antenna at the base equals the current flowing into the source
through the ground. This ground current results in I^2 * R loss; radials
reduce the R and therefore the loss.

In the case of a "ground plane" antenna with highly elevated radials,
the radials provide a path for the base current to flow (again, current
out of the source -- into the antenna -- has to equal the current into
it -- from the radials). Because of the physical configuration, it's
sometimes more convenient to build an antenna this way instead of making
a dipole. The radials radiate very little, and the vertical section
radiates twice as much per unit length as a dipole, resulting in the
same overall gain and pattern.

If it is the first then what does the 'efficiency' curve look like for a
shortened, loaded, vertical? That is if the vertical element is loaded
to resonate at 1/5 of a half wave length what does the ground resistance
profile look like for 120 radials at various lengths of 1/20 wave, 1/10
wave and 1/5 wave?

The answer to this depends on the ground conductivity and frequency. But
the radiation resistance of the shortened antenna will be less than that
of a full-height one. Therefore, if the ground resistance is fixed and
determined by the ground system (not completely true -- it does depend
some on the antenna height -- but close enough for discussion), the
efficiency of the short antenna will be less than for a full-height one.
I recommend finding and reading "The W2FMI Ground-Mounted Short
Vertical", by Jerry Sevick, W2FMI in March 1973 QST. He built several
antennas very much like you describe and made extensive measurements.


The question I am really driving at is if mesh is layed down at 100%
coverage about what fraction of a wave length needs to be covered to
create a 2.5, 5, and 10 ohm equivalent ground for the vertical above?

Sorry, I don't know the answer to that one right off the bat. It could
be determined with NEC-4 modeling, but I don't have time to do that. I
suggest that you locate a copy of Brown, Lewis, and Epstein's paper
"Ground Systems as a Factor in Antenna Efficiency", now posted on the
web. You should be able to get a fairly good idea from their
measurements of 113-radial systems.


In the paragraph above is the mesh simulating a ground or is it fact
operating as a ground.

I really don't know what "simulating a ground" and "operating as a
ground" means. But the radial field doesn't act like either real Earth
or a perfect infinite plane, if that's what you mean. If sufficiently
fine, a mesh will act like a solid conductor the size of the mesh.

Roy Lewallen, W7EL

MK,

How satisfying it is to read your message, written in plain, easy to
understand, well-punctuated English, without any undeciferable coded
abbreviations.

I agree with what you say although I am unfamiliar with exactly how
the FCC fits into the scheme of things.

Amateurs and commercial broadcasters have a common fundamental
requirement. There is a service area to be covered with a given field
strength. Depending on frequency, requirements then diverge. But the
design methods used to satisfy requirements are all confined (or
should be) to the principles of engineering economics. Inevitably, the
Dollar, Pound, Frank, Mark, Rouble and the Yen rule the roost.

Both commercial broadcasters and amateurs do a cost-befit analysis.
The broadcaster takes into account the revenue acruing from selling
the service. The amateur, whether he likes it or not, has to ask
himself what the satisfaction of using the station is worth.

Amateurs' bank accounts are not unlimited.

Field strength at the limits of the service area depends on the power
efficiency of the radiating system. If engineering economics dictate
use of a set of buried ground radials then the peformance of the
ground radials must be included. Considering the system as a whole,
it may be economical NOT to achieve the maximum possible radiating
efficiency. Indeed, the maximum is seldom the target.

If there is an economical choice in the matter, once the location of
the station is decided, everybody agrees that efficiency depends on
soil resistivity at the site. To estimate efficiency it is necessary,
at the very least, to make a guess at soil resistivity. Perhaps just
by looking at the type of weeds growing in it. Or it can be measured.

Depending on how far it enters into station economics, it is possible
to numerically estimate efficiency from the number and length of
radials AND FROM SOIL RESISTIVITY.

B.L & E and the FCC don't enter into it.
----
Reg.

========================================
MK wrote,
The only stations that the FCC is concerned about is commercial.
And the reason they stick with the standard number is for stability
and getting the max bang for buck, and an easily expected
performance level. Buying a load of wire will beat using more
transmitter power over the long run. If they use 120 radials,
they know they will be getting close to maximum performance.
If they don't, it's a crap shoot. 120 radials *will* outperform
16 of them. There is no question, unless they are over sea
water. I'm not saying hams have to run that many. In fact, I
think 60 will do for most, except the most hard core for good
results. Even less for the more casual user.
But I have no problems with the FCC wanting a certain level
of performance for commercial stations. I have no problems
seeing why they do it either. Wire is cheap compared to
todays level of monthly light bill. With some stations, the
radials,
or lack of , in certain directions gives them a controlable
pattern with no surprises in f/s over a period of time
with changing ground conditions. The main thing is
stability of performance over periods of time. Or thats
my take anyway.
MK

On Wed, 7 Sep 2005 14:07:39 +0000 (UTC), "Reg Edwards"
wrote:

MK,

How satisfying it is to read your message, written in plain, easy to
understand, well-punctuated English, without any undeciferable coded
abbreviations.

I agree with what you say although I am unfamiliar with exactly how
the FCC fits into the scheme of things.

Amateurs and commercial broadcasters have a common fundamental
requirement. There is a service area to be covered with a given field
strength. Depending on frequency, requirements then diverge. But the
design methods used to satisfy requirements are all confined (or
should be) to the principles of engineering economics. Inevitably, the
Dollar, Pound, Frank, Mark, Rouble and the Yen rule the roost.

Both commercial broadcasters and amateurs do a cost-befit analysis.
The broadcaster takes into account the revenue acruing from selling
the service. The amateur, whether he likes it or not, has to ask
himself what the satisfaction of using the station is worth.

Amateurs' bank accounts are not unlimited.

Field strength at the limits of the service area depends on the power
efficiency of the radiating system. If engineering economics dictate
use of a set of buried ground radials then the peformance of the
ground radials must be included. Considering the system as a whole,
it may be economical NOT to achieve the maximum possible radiating
efficiency. Indeed, the maximum is seldom the target.

If there is an economical choice in the matter, once the location of
the station is decided, everybody agrees that efficiency depends on
soil resistivity at the site. To estimate efficiency it is necessary,
at the very least, to make a guess at soil resistivity. Perhaps just
by looking at the type of weeds growing in it. Or it can be measured.

Depending on how far it enters into station economics, it is possible
to numerically estimate efficiency from the number and length of
radials AND FROM SOIL RESISTIVITY.

B.L & E and the FCC don't enter into it.
----
Reg.

Sorry to disagree, Reg, but it appears you're overlooking an important
point--the difference between the efficiency of the radiating system
itself, versus the efficiency of the ground area external to the
radiating system.

BL&E shows that when 90 - 120 (actually 113) radials of 0,4 w/l form
the ground system for a 1/4 wl radiator, the efficiency is 98.7%
efficient, REGARDLESS OF THE SOIL RESISTIVITY UNDER THE RADIALS. This
is shown by obtaining the field strength of 192 mv/meter at 1 mile for
1000 watts delivered to the antenna under the conditions described
above, compared to 194.5 mv/meter with a perfect ground having an
efficiency of 100%

It is only the soil resistivity of the ground external to the radial
system that determines the field stength external to the radial
system. Consequently, the soil resistivity (or conductivity, if you
like) is significant only in the areas external to the radial system.

Walt, W2DU

On Wed, 07 Sep 2005 11:41:33 -0400, Walter Maxwell
wrote:

Sorry to disagree, Reg, but it appears you're overlooking an important
point--the difference between the efficiency of the radiating system
itself, versus the efficiency of the ground area external to the
radiating system.

Walter, my friend, you're beating a dead horse. It would appear that
Reg's mind is made up and no amount factual proof is going to change
it.

Had BL&E been Englishmen I sure things would be different.G

73,
Danny, K6MHE

On Wed, 07 Sep 2005 09:39:28 -0700, Dan Richardson wrote:

On Wed, 07 Sep 2005 11:41:33 -0400, Walter Maxwell
wrote:

Sorry to disagree, Reg, but it appears you're overlooking an important
point--the difference between the efficiency of the radiating system
itself, versus the efficiency of the ground area external to the
radiating system.

Walter, my friend, you're beating a dead horse. It would appear that
Reg's mind is made up and no amount factual proof is going to change
it.

Had BL&E been Englishmen I sure things would be different.G

73,
Danny, K6MHE

Good point, Danny, how true.

Walt

Dan Richardson wrote -
Had BL&E been Englishmen I sure things would be different.G
====================================

They sure would!

They would have been instructed to go back and finish the job.
----
Reg.

Dan Richardson wrote -
Had BL&E been Englishmen I sure things would be different.G
====================================

They sure would!

They would have been instructed (by their employers) to go back and
finish the job.
----
Reg.

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

I am reminded of the military engineer who was dispatched by Napolion,
an engineer himself, in connection with standardisation of the Metre,
to measure the distance between the Earth's Equator and the North
Pole.

Measurements began, but the further the engineer departed from his
beautiful lady friend in Paris the more difficult it became to make
progress along the route. Eventually, he couldn't withstand the mental
and physical stress. He returned to her Parisian boudoir and resorted
to cooking the books in what time he had to spare.

So, the International Standard of Length, The Metre, held in Paris,
France, carefully guarded by the German occupying forces during WW2,
may or may not be equal to 39.37 English inches.

Actually, the most fundamental physical measurement standard is the
Mass of the Standard Kilogram on which everything else depends. But it
is quite an arbitrary quantity.

I have just finished a bottle of Blossom Hill, Californian, white
wine. Makes a pleasant change to arguing about what 'amateurs' BL&E
might, or might not have done before leaving the site.
----
Reg.

Reg Edwards wrote:

Dan Richardson wrote -
Had BL&E been Englishmen I sure things would be different.G
====================================

They sure would!

They would have been instructed (by their employers) to go back and

finish the job.

----
Reg.


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

I am reminded of the military engineer who was dispatched by Napolion,
an engineer himself, in connection with standardisation of the Metre,
to measure the distance between the Earth's Equator and the North
Pole.

Measurements began, but the further the engineer departed from his
beautiful lady friend in Paris the more difficult it became to make
progress along the route. Eventually, he couldn't withstand the mental
and physical stress. He returned to her Parisian boudoir and resorted
to cooking the books in what time he had to spare.

So, the International Standard of Length, The Metre, held in Paris,
France, carefully guarded by the German occupying forces during WW2,
may or may not be equal to 39.37 English inches.

Actually, the most fundamental physical measurement standard is the
Mass of the Standard Kilogram on which everything else depends. But it
is quite an arbitrary quantity.

I have just finished a bottle of Blossom Hill, Californian, white
wine. Makes a pleasant change to arguing about what 'amateurs' BL&E
might, or might not have done before leaving the site.
----
Reg.


All the above is/maybe true but remember that all the formule work using
the values represented in the METRE and the KILOGRAM. Something must be
correct here....

Dave WD9BDZ