Length & number of radials
 

Hasan et al,

Tom says current can be detected in radials well beyond the 20dB
attenuation limit. This is easily explained.

The total current flowing in the system at a distance is in the soil
due to its far greater cross-sectional area. Especially when soil
resistivity is low. Nothing in particular happens in the soil at the
end of the 20dB limit.

The small current in a radial is INDUCED in it by the relatively
larger total current flowing in the soil in parallel with it. The
radial current is NOT generated by the voltage at its input. Its high
attenuation isolates it from its input.

What current flows in a radial has a progressively less effect on the
total current (which is what matters) as distance increases.
Eventually, it doesn't matter whether the radial is there or not.

The limit is reached when the radial input impedance converges on Zo,
the radial's characteristic impedance. This occurs when radial
attenuation is around 18 or 20dB. Beyond that distance the current
flowing in the ground carries on, as usual, unaffected whether the
radial is there or not.

Resonant effects, small peaks and troughs in the impedance-frequency
curve, also die away at the 20dB or even lower limit. There's not much
left even at 14dB.

Radial attenuation increases rapidly with frequency. So shorter
radials can be used at 14 MHz than at 1.9 MHz. When 30 MHz is the
lowest frequency of use, and soil resistivity is high, a dipole,
without radials, is more likely to be used than a vertical.

(Comment: I guessed correctly I would be accused of trolling when I
introduced the subject of radials as transmission lines.)
----
Reg, G4FGQ.

Length & number of radials
 

Wash your hands before opening that next bottle.

73's
Richard Clark, KB7QHC

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

Like Bob Hope, when in your company, I always drink out of a dirty
glass.
----
Reg.

Length & number of radials
 

Richard Clark wrote:
I have to ask, is it written in sonnet form in middle English?

Almost as bad, it is written in PASCAL. :-)
--
73, Cecil http://www.qsl.net/w5dxp

Length & number of radials
 

hasan schiers wrote:

Are you saying (for example), that the feedpoint R of a 1/4 w vertical
against perfect ground cannot be reliably estimated at 37 ohms?

No. I'm not saying that.

If it can,
then isn't 37/R a measure of efficiency?

No. A ground can have transmission line effects. As such, it can modify
impedances.

Is it really possible to reduce ground losses to the absolute minimum and
not have a corresponding increase in field strength?

You are assuming a reduction of ground loss or an increase of ground
loss always indicates a certain resistance change at the feedpoint.
That assumption is not correct Hans.

For example, I can measure feed resistance of a mobile antenna on my
truck. By moving the antenna around I can vary the "apparent" ground
resistance from a few ohms to perhaps 30 ohms with very little change
in ground loss.

All I'm saying is the feedpoint reistance change when using a 1/4 wl
series fed radiator does not correspond to change in field strength. I
know that to be absolutely true, because I and others have seen that
happen.

73 Tom

Length & number of radials
 

Reg,

I certainly don't think you are trolling. You have aroused a very
interesting discussion. I'm absolutely fascinated. The issue isn't whether
Tom can detect the current at a point beyond your description. The point is
will that current be quite a bit larger than the 20 dB down your approach
predicts.

This is getting pretty simple...either the current is or isn't substantial
beyond the wire lengths you describe. If it isn't, you have hit on
something big. If it is, then the model you are using or the application of
that model is in error. I'm just trying to learn which of these two cases is
true. I find your analysis breathtakingly interesting. It's just hard to
resolve the apparent contradictions....fun nevertheless! Thanks again.

....hasan, N0AN
"Reg Edwards" wrote in message
...
Hasan et al,

Tom says current can be detected in radials well beyond the 20dB
attenuation limit. This is easily explained.

The total current flowing in the system at a distance is in the soil
due to its far greater cross-sectional area. Especially when soil
resistivity is low. Nothing in particular happens in the soil at the
end of the 20dB limit.

The small current in a radial is INDUCED in it by the relatively
larger total current flowing in the soil in parallel with it. The
radial current is NOT generated by the voltage at its input. Its high
attenuation isolates it from its input.

What current flows in a radial has a progressively less effect on the
total current (which is what matters) as distance increases.
Eventually, it doesn't matter whether the radial is there or not.

The limit is reached when the radial input impedance converges on Zo,
the radial's characteristic impedance. This occurs when radial
attenuation is around 18 or 20dB. Beyond that distance the current
flowing in the ground carries on, as usual, unaffected whether the
radial is there or not.

Resonant effects, small peaks and troughs in the impedance-frequency
curve, also die away at the 20dB or even lower limit. There's not much
left even at 14dB.

Radial attenuation increases rapidly with frequency. So shorter
radials can be used at 14 MHz than at 1.9 MHz. When 30 MHz is the
lowest frequency of use, and soil resistivity is high, a dipole,
without radials, is more likely to be used than a vertical.

(Comment: I guessed correctly I would be accused of trolling when I
introduced the subject of radials as transmission lines.)
----
Reg, G4FGQ.

Length & number of radials
 

On Fri, 21 Jul 2006 11:28:02 -0500, "hasan schiers" wrote:


"Reg Edwards" wrote in message
...

In the case of RADIAL_3 the obvious purpose of the program is to
assist with choosing an economic length and number of radials to be
used with a given test antenna height. It is also educational in that
after reading the introductory notes and using it, the user will have
a better understanding of how radials work.
snip

================================================= ======
We need to know: does the predicted attenuation of current along a radial
wire happen as quickly as you predict? This can be measured. This can be
modeled. That's what makes this fun. Let's find out. Let's see what agrees
with what and what doesn't. Then we can conjecture as to why, and which
approach is to be "believed".
================================================= =======
snip
...hasan, N0AN

I've been reading this thread, and sent the following msg to hasan. I then
decided to post it here for others to see.

Walt, W2DU

Hi Hasan,

I've been reading the radials thread on the rraa, with the works of BLE bandied
about. I have a copy of BLE in PDF that I can put on a CD and mail it to you if
you don't have a copy, which I'd be pleased to do.

Incidentally, I worked for many years with Jess Epstein, the 'E' of BLE, in
Brown's antenna laboratory at the RCA Labs in Princeton, where Brown is the 'B'
in BLE. I also know Bob Lewis, the 'L' in BLE, as we've spent many hours
together as hams. Bob is W2EBS.

Bob and I were attending a ham meeting in NJ in the 1960s where Jerry Sevick was
demonstating how radials worked with verticals. He had annular rings of wire
connecting all the radials at various radial distances from the center. He even
had a wire connecting the ends of all the radials together. I asked him what the
annular rings were for, and he replied that they kept the currents in each
radial equal. I asked him if he was acquainted with the BLE paper, and he said
he had heard of it but was not familiar with it. So I asked him if he'd like one
of it's co-authors to explain it He agreed, but was totally shocked to know
that Bob Lewis was in his audience. Bob then proceded to straighten Sevick out
on how radials worked. A fun night, indeed.

The graphs reporting BLE's measurements are pretty conclusive. In addition, the
BLE paper is the basis on which the FCC set the requirements for the ground
systems on all AM BC stations since 1939. So there's thousands of empirical
proofs of the correctness of their measurements in every situation where field
strengh measurements were required for proof of performance.As I'm sure you
already know, for every AM BC station that uses a directional antenna system the
FCC requires field strength measurements. There has never been any such
measurements that disagreed with those of BLE. Even Tom's (W8JI)

Please let me know if you'd like me to burn you a copy of BLE.

Walt,W2DU

PS--If any others reading this would like a copy of BLE let me know and I'll
burn it for you.

Length & number of radials
 

wrote in message

No. A ground can have transmission line effects. As such, it can modify
impedances.

Bummer! I had no idea.


Hasan: Is it really possible to reduce ground losses to the absolute
minimum and
not have a corresponding increase in field strength?

Tom: You are assuming a reduction of ground loss or an increase of ground
loss always indicates a certain resistance change at the feedpoint.
That assumption is not correct Hans. (Hasan)

Bummer again! The field strength does change, but you are saying the
feedpoint Z may not track it.

All I'm saying is the feedpoint reistance change when using a 1/4 wl
series fed radiator does not correspond to change in field strength. I
know that to be absolutely true, because I and others have seen that
happen.

Then we are left with no use for monitoring feedpoint resistance (other than
matching). Bummer.
All we can do is keep adding radials and watch the R drop until it gets
boring. (Or is that not possible now, either?). Every vertical antenna (1/4
w), I've ever made and played the radial game with has behaved predictably
with increasing numbers of radials...the feedpoint Z has always dropped
asymptotically towards the Rrad of the vertical. Now I have to discard all
that...or are you quoting the exception that doesn't invalidate the general
nature of things? I'm getting that "too many variables to deal with" black
magic feeling again. Things looked so reasonable for a while there...now it
appears for all but the brave, it becomes nothing more than cramming a lot
of wire into or onto the ground and hoping for the best.

Not what I was hoping for at all. Bummer.

Thanks for taking the time to explain parts of this, Tom. (even though it
wasn't what I wanted to hear)

73,

....hasan, N0AN


73 Tom

Length & number of radials
 

"Walter Maxwell" wrote
The graphs reporting BLE's measurements are pretty conclusive. In
addition, the
BLE paper is the basis on which the FCC set the requirements for the
ground
systems on all AM BC stations since 1939

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

Walt, where've you been lately?

I have no doubt that BLE measurements are good and valid at LF and
below. But to extrapolate conclusions up to HF, where amateurs reside,
and where funny things happen to radials, is somewhat dangerous.

I understand BLE forgot to measure ground resistivity and permittivity
of the site. Perhaps because they thought it didn't matter very much.
But such things certainly matter above about 3.5 MHz. At HF radials
behave very differently from behaviour at LF if only because the
ground 'constants' have changed from their DC and LF values (which are
the values usually inserted in HF computer programs.)
----
Reg.

Length & number of radials
 

"Walter Maxwell" wrote (in part):
I've been reading the radials thread on the rraa, with the works of BLE
bandied
about. I have a copy of BLE in PDF that I can put on a CD and mail it to
you if
you don't have a copy, which I'd be pleased to do.
___________

All,

Not to minimize the fine offer of Mr. Maxwell, any of you who might prefer
to download a PDF of this BL&E "benchmark" paper with empirical data on
buried radial ground systems vs radiation system efficiency can do so from
the link following the text below, which I posted last December to some
broadcast-oriented websites.

N. B. for/to REG EDWARDS (G4FQP): I hope that you will be motivated to
follow through on one or the other of these offers, and that you will post a
comparison of the results of your ready-to-run, "radial_3" DOS program as
compared to the BL&E datum, for equivalent conditions.

RF

+++

Link: Brown, Lewis & Epstein Paper on MW Ground Systems
Richard Fry (rfry at adams.net )
Fri Dec 9 14:54:23 CST 2005

--------------------------------------------------------------------------------

After some "back and forth," IEEE just gave me permission to post the
benchmark 1937 paper by Brown, Lewis and Epstein about MW ground systems.

Quite a few on RT and BC asked me earlier for this, but I had to hold off
until it was possible. Now I hope all those who asked will see this posting,
eventually, and view/download it from the link below. There are some
restrictions on its use, as shown in the PDF.

The file size is about 3.3 megs, so a fast connection will help.

http://rfry.org/Software%20&%20Misc%20Papers.htm

RF

Length & number of radials
 

Hi Hasan,

I have not forgotten your model. I am very interested in verifying
the findings of Reg's program, so will get around to it. I will be
very busy this weekend, so may not have a chance until the
beginning of next week. I have been investigating some of
the limitations of NEC, and 1 mm below ground is one of
them (Not necessarily because of the depth, but segmentation
issues). I will try and get as close to your model parameters
as possible. This afternoon I was sidetracked by a challenge
from Reg, and spent about 90 minutes running a model
similar to yours. Interestingly enough there appears to be
a very large discrepancy between the programs.
NEC 4.1 indicated only 30.5 % efficiency.
(See later thread).

Frank


"hasan schiers" wrote in message
...
Hi Frank,

I think the general question became "can one use this Rrad value in
calculating efficiency". I'm waiting for Tom's response to my last
posting.

On the other issue, radial length vs. usefulness, (I tried a diect mail
to you and it didn't make it cuz I forgot to take out the nospam part),

here is what I want to know from NEC-4:

Radial wire is #14 THHN inslulated wire. I approximated it at 2mm. The
antenna wire is 4 mm. For these purposes, you can probably forget that the
wire is insulated.

Now...looking at radial length (assuming 26 radials), and given the
constants I previously provided, how long does a radial in this
configuration have to be, before it is no longer valuable to increase its
length. Tom says he measured significant current in a radial well beyond
where Reg's program says the current had diminished to insignifcant
levels.

I would be MOST interested if you can confirm Tom's measurements. If NEC-4
says there is substantial radial current where Reg's program says there
isn't, then that is an important contradiction, putting Reg's model into
question. I'm giving more credibility to NEC-4 (properly used) than I am
to Reg's own design. If, however, we have two sources (one measurement
based: Tom, one model based: NEC-4), that say Reg's theory that radials
quickly approach maximum effectiveness over a MUCH shorter run than has
been previously understood (in moderate to very good soils), that
contradict Reg's algorithim.

Having only looked at conclusions from BL&E, I can't say what their
measurements indicated in terms of radial current vs. length. Ian has
suggested that they did measure the radial current vs length and they
concur with Tom. So, if BL&E and Tom (both empirical), as well as NEC-4
(model based), all say that important levels of current are present in
radials well beyond where Reg's program predicts, then there's only one
conclusion left. (Unless I'm missing something).

This, to me, is much more interesting stuff than a month long peeing
contest over precipitation static.(which may be rearing its ugly head yet
again in the "double bazooka" thread. God help us!

73, and thanks for your comments and efforts to help me understand what is
going on.

...hasan, N0AN
"Frank's" wrote in message
news:ZO5wg.115459$A8.61548@clgrps12...
I understand there are measurement issues (and certainly assumption
issues
for Rrad). Isn't is fairly certain that increasing the number of radials
(of proper length) until the feedpoint R (at resonance, at the antenna)
no longer drops, is a reasonable approximation of "high efficiency"? The
only issue I see, is determining the target Rrad to compare it to when
trying to "estimate" efficiency.

Are you saying (for example), that the feedpoint R of a 1/4 w vertical
against perfect ground cannot be reliably estimated at 37 ohms? If it
can, then isn't 37/R a measure of efficiency?

Again, I'm thinking of the efficiency of the ground system... I have no
way to look at field strength.

Is it really possible to reduce ground losses to the absolute minimum
and not have a corresponding increase in field strength?

This is starting to turn into "black magic" for me. I can understand
questioning a particular "number" for efficiency based on the simplistic
Rrad/R formula. If the implications go further...indicating there is no
meaning to Rrad/R, then I'm lost.

Perhaps the issue is that it's known how to maximize efficiency, it's
just completely unknown what that efficiency really is, and there is no
simple way to measure it. If that's what your saying, then I understand.

That position does seem to muddy up the "how many radials and of what
length" efficiency info presented in ON4UN's book and referenced in
other texts. They all seem to acccept some sort of accuracy for the
Rrad/R formula with 1/4 w verticals. If I understand you correctly, the
formula is rejected outright as hopelessly simplistic, and of no
particular value.

Do I have it now? If so, I'll refrain from using it in the future.

I had always assumed that a NEC model of a perfectly conducting
monopole above a perfect ground would provide the radiation
resistance. For example, considering your antenna of 18.3 m
at 3.62 MHz, the input impedance is 27.5 - j 64.7. The radiation
resistance would therefore be 27.5 ohms. This appears to be
fairly close to your estimate of 25.4 ohms.

Frank

Length & number of radials
 

On Fri, 21 Jul 2006 23:04:54 +0100, "Reg Edwards"
wrote:


"Walter Maxwell" wrote
The graphs reporting BLE's measurements are pretty conclusive. In
addition, the
BLE paper is the basis on which the FCC set the requirements for the
ground
systems on all AM BC stations since 1939

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

Walt, where've you been lately?

I have no doubt that BLE measurements are good and valid at LF and
below. But to extrapolate conclusions up to HF, where amateurs reside,
and where funny things happen to radials, is somewhat dangerous.

I understand BLE forgot to measure ground resistivity and permittivity
of the site. Perhaps because they thought it didn't matter very much.
But such things certainly matter above about 3.5 MHz. At HF radials
behave very differently from behaviour at LF if only because the
ground 'constants' have changed from their DC and LF values (which are
the values usually inserted in HF computer programs.)
----
Reg.

Hi Reg,

I'll admit to being away from rraa for quite a while. A good bit of the time
away was while finishing the writings for Reflections 3, which includes several
new chapters, some of which archive a portion of my escapades in designing
antennas for various spacecraft, including those that flew on the World's first
weather satellite, TIROS 1. I was fortunate in being at the right place at the
right time when the space age began. Those were the years I spent with Jess
Epstein, the 'E' of the BLE team. Some of the additional material that went into
Reflections 3 is available on my web page at www.w2du.com. I think you might
find Chapters 19A and 21A of interest.

From eavesdropping on the banter between you and Richard C it's easy to see that
your winery has kept your mental physique it top shape. I hope that your
physical physique continues at least in its present condition.

Getting now to BLE, I agree with you concerning the changes in ground
characteristics at HF compared with MF and LF. I don't know if you have a copy
of BLE, but you should know that the BLE experiments were performed at 3 MHz.
Please let me know if you have BLE, because I'd like to email you a copy if you
don't. It will demonstrate the hundreds of measurements taken meticulously to
arrive at the conclusions reported in their paper of 1937.

Of the many results of various combinations of radial lengths and numbers of
radials, the one that that stands out in my mind is the combination of the
longest radial, 0.412 lambda, with the maximum number or radials, 113. This
combination achieved near-perfect ground, yielding a field strength of 192 mv/m,
as compared to the theoretical maximum of 196 mv/m, achieved with perfect
ground. The reference for these numbers is 1000 watts delivered to the antenna
and measured at 1 mile. Notice that the difference between the ideal and actual
field strengths is only 2 percent.

Reg, concerning the difference in ground characteristics with frequencies above
3.5 MHz, please consider this. When the radials are long enough, and enough of
them spaced sufficiently close, the effect is that of nearly perfect ground,
regardless of the actual ground characteristics beneath the radials. Let's
consider a comparison. First, few radials widely spaced. Displacement currents
reach the ground everywhere surrounding the vertical radiator. Currents entering
the ground between the radials diffract toward the nearest radial of higher
conductivity. During its travel toward the radial it naturally encounters the
resistance of the ground. However, with many radials more closely spaced,
currents now entering the ground have a shorter resistance path in reaching the
nearest radial, approaching a negligible value.

My point is that when there is a sufficient number of radials of sufficient
length to approach a nearly-perfect ground, the ground characteristics beneath
the radials are irrelevant within the area they cover in determining the
terminal impedance and efficiency of the radiator. Therefore, the different gr
ound characteristics that prevail as the frequency increases above 3.5 MHz are
also irrelevant. This is not to say that the ground characteristics away from
the immediate area are not important.

You might get a chuckle concerning the number of radials being 113. The original
plan was to plow in 100 radials. When the grunts Jess Epstein and Bob Lewis had
plowed in the intended 100 there was wire left over on the spool. They asked
Brown what they should do with the remaining wire, he said, "Plow it in." The
remainder of the wire allowed just 13 more radials to be plowed in.

On a personal note, I engineered and built WCEN in Mt. Pleasant, Michigan, 500 w
on 1150 Kc (it was 'Kc' then), with a 300' Blau-Knox tower. I plowed in 120
radials. My Dad manufactured the plow, which I rode, while he drove the tractor.

Hope this keeps ya busy fer a while,

Walt, W2DU

Length & number of radials
 

On Sat, 22 Jul 2006 18:04:52 -0400, Walter Maxwell
wrote:

[snip]

Getting now to BLE, I agree with you concerning the changes in ground
characteristics at HF compared with MF and LF. I don't know if you have a copy
of BLE, but you should know that the BLE experiments were performed at 3 MHz.
Please let me know if you have BLE, because I'd like to email you a copy if you
don't. It will demonstrate the hundreds of measurements taken meticulously to
arrive at the conclusions reported in their paper of 1937.


Hi Walter, nice to see you back.

For Reg, or anyone else for that matter, the BLE paper is available at
http://k6mhe.com/BLE.html

73,

Danny, K6MHE

Length & number of radials
 

"Walter Maxwell" wrote
The graphs reporting BLE's measurements are pretty conclusive. In
addition, the
BLE paper is the basis on which the FCC set the requirements for
the
ground
systems on all AM BC stations since 1939

==========================================
My point is that when there is a sufficient number of radials of
sufficient
length to approach a nearly-perfect ground, the ground
characteristics beneath
the radials are irrelevant within the area they cover in determining
the
terminal impedance and efficiency of the radiator. Therefore, the
different gr
ound characteristics that prevail as the frequency increases above
3.5 MHz are
also irrelevant.
Walt, W2DU
============================================

Dear Walt,

At risk of upsetting a great number of patriotic USA citizens, all BLE
hero-worshippers, I admit to having speed-read BLE's lengthy paper
some years back. Their conclusion, that with a sufficiant number and
length of radials the ground characteristics are irrelevant, is so
glaringly apparent they could have stayed in their offices and saved a
great deal of expense and copper wire. I am reminded of John Cleese's
remark "They must have had first-class honors degrees in stating the
bleeding obvious".

Because BL&E omitted to measure ground conductivity and permittivity
on the site their conclusion amounted to making a virtue out of a vice
and Marzipan the Magician's magic number of 120 came into existence.
Their sponsors should have made them go back to finish the job.

In the absence of any other information at the time, the fact of
irrelevance was of interest to LF and MF broadcasters with money to
burn, but it was, and still is, of no use to radio amateurs, confined
to the HF bands with limited purses, small back yards and XYL's to
keep happy.

My small program Radial_3 has been singled out and I have been accused
of disagreeing in a disruptive, almost criminal manner with BL&E's
conclusions. This is patently untrue! The program has nothing to do
with BL&E except that it deals with a similar subject in terms
appropriate to amateurs and draws its own independent conclusions.

Your absence caused a little worry. Glad to hear you were only
working.
----
Reg.

Length & number of radials
 

"Richard Fry" wrote
N. B. for/to REG EDWARDS (G4FQP): I hope that you will be
motivated to
follow through on one or the other of these offers, and that you
will post a
comparison of the results of your ready-to-run, "radial_3" DOS
program as
compared to the BL&E datum, for equivalent conditions.

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

What equivalent conditions? Where can they be found? What was the
ground resistivity and permittivity on BL&E's site?

I am not motivated to do anything except reply to your remarks. You
are making a song and dance about it.

If anybody wishes to confirm or deny the usefulness of program
Radial_3 then all they have to do is do what I have done and bury a
few ( not 120 ) wires in their back yard and get on the HF bands.

Proof of the pudding lies in the eating!
----
Reg.

Length & number of radials
 

Hi Walt
Reading the words "plow it in" made me chuckle.
I always had the same attitude building AM broadcast antennas.
If there was wire left over, I'd "plow it in".
73
H.
NQ5H

"Walter Maxwell" wrote in message
...
On Fri, 21 Jul 2006 23:04:54 +0100, "Reg Edwards"

wrote:


"Walter Maxwell" wrote
The graphs reporting BLE's measurements are pretty conclusive. In
addition, the
BLE paper is the basis on which the FCC set the requirements for the
ground
systems on all AM BC stations since 1939

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

Walt, where've you been lately?

I have no doubt that BLE measurements are good and valid at LF and
below. But to extrapolate conclusions up to HF, where amateurs reside,
and where funny things happen to radials, is somewhat dangerous.

I understand BLE forgot to measure ground resistivity and permittivity
of the site. Perhaps because they thought it didn't matter very much.
But such things certainly matter above about 3.5 MHz. At HF radials
behave very differently from behaviour at LF if only because the
ground 'constants' have changed from their DC and LF values (which are
the values usually inserted in HF computer programs.)
----
Reg.

Hi Reg,

I'll admit to being away from rraa for quite a while. A good bit of the
time
away was while finishing the writings for Reflections 3, which includes
several
new chapters, some of which archive a portion of my escapades in designing
antennas for various spacecraft, including those that flew on the World's
first
weather satellite, TIROS 1. I was fortunate in being at the right place at
the
right time when the space age began. Those were the years I spent with
Jess
Epstein, the 'E' of the BLE team. Some of the additional material that
went into
Reflections 3 is available on my web page at www.w2du.com. I think you
might
find Chapters 19A and 21A of interest.

From eavesdropping on the banter between you and Richard C it's easy to
see that
your winery has kept your mental physique it top shape. I hope that your
physical physique continues at least in its present condition.

Getting now to BLE, I agree with you concerning the changes in ground
characteristics at HF compared with MF and LF. I don't know if you have a
copy
of BLE, but you should know that the BLE experiments were performed at 3
MHz.
Please let me know if you have BLE, because I'd like to email you a copy
if you
don't. It will demonstrate the hundreds of measurements taken meticulously
to
arrive at the conclusions reported in their paper of 1937.

Of the many results of various combinations of radial lengths and numbers
of
radials, the one that that stands out in my mind is the combination of the
longest radial, 0.412 lambda, with the maximum number or radials, 113.
This
combination achieved near-perfect ground, yielding a field strength of 192
mv/m,
as compared to the theoretical maximum of 196 mv/m, achieved with perfect
ground. The reference for these numbers is 1000 watts delivered to the
antenna
and measured at 1 mile. Notice that the difference between the ideal and
actual
field strengths is only 2 percent.

Reg, concerning the difference in ground characteristics with frequencies
above
3.5 MHz, please consider this. When the radials are long enough, and
enough of
them spaced sufficiently close, the effect is that of nearly perfect
ground,
regardless of the actual ground characteristics beneath the radials. Let's
consider a comparison. First, few radials widely spaced. Displacement
currents
reach the ground everywhere surrounding the vertical radiator. Currents
entering
the ground between the radials diffract toward the nearest radial of
higher
conductivity. During its travel toward the radial it naturally encounters
the
resistance of the ground. However, with many radials more closely spaced,
currents now entering the ground have a shorter resistance path in
reaching the
nearest radial, approaching a negligible value.

My point is that when there is a sufficient number of radials of
sufficient
length to approach a nearly-perfect ground, the ground characteristics
beneath
the radials are irrelevant within the area they cover in determining the
terminal impedance and efficiency of the radiator. Therefore, the
different gr
ound characteristics that prevail as the frequency increases above 3.5
MHz are
also irrelevant. This is not to say that the ground characteristics away
from
the immediate area are not important.

You might get a chuckle concerning the number of radials being 113. The
original
plan was to plow in 100 radials. When the grunts Jess Epstein and Bob
Lewis had
plowed in the intended 100 there was wire left over on the spool. They
asked
Brown what they should do with the remaining wire, he said, "Plow it in."
The
remainder of the wire allowed just 13 more radials to be plowed in.

On a personal note, I engineered and built WCEN in Mt. Pleasant, Michigan,
500 w
on 1150 Kc (it was 'Kc' then), with a 300' Blau-Knox tower. I plowed in
120
radials. My Dad manufactured the plow, which I rode, while he drove the
tractor.

Hope this keeps ya busy fer a while,

Walt, W2DU

Length & number of radials
 

I'm often confronted with problems as a physicist where one can only get a
handle on upper and lower bounds.
Lower bound:
I'd say the minimum number and length of radials is 3 (must define a plane)
and 1/4 wavelength (satisfies boundary conditions).

Upper (infinite sheet of copper)
As Walt and Reg have debated, the "Cleese extreme" (to steal from Reg's
post) is trying to duplicate the "infinite perfectly conducting plane" of
our elementary physics books.
Cheers and beers
H.

73, NQ5H

Length & number of radials
 

"H. Adam Stevens, NQ5H" wrote
I'm often confronted with problems as a physicist where one can only
get a
handle on upper and lower bounds.
Lower bound:
I'd say the minimum number and length of radials is 3 (must define a
plane)
and 1/4 wavelength (satisfies boundary conditions).

Upper (infinite sheet of copper)
As Walt and Reg have debated, the "Cleese extreme" (to steal from
Reg's
post) is trying to duplicate the "infinite perfectly conducting
plane" of
our elementary physics books.
Cheers and beers

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

Yes Adam, a logical way of looking at it.

Associated with any number there is always another number which is
sometimes, but not often enough, used to describe its uncertainty.

But nearly always it takes much longer to determine the uncertainty
than it does to arrive at the first number, especially if the first
number is the result of a measurement.
----
Reg.

Length & number of radials
 

On Sun, 23 Jul 2006 06:24:02 +0100, "Reg Edwards"
wrote:


"Walter Maxwell" wrote
The graphs reporting BLE's measurements are pretty conclusive. In
addition, the
BLE paper is the basis on which the FCC set the requirements for
the
ground
systems on all AM BC stations since 1939

==========================================
My point is that when there is a sufficient number of radials of
sufficient
length to approach a nearly-perfect ground, the ground
characteristics beneath
the radials are irrelevant within the area they cover in determining
the
terminal impedance and efficiency of the radiator. Therefore, the
different gr
ound characteristics that prevail as the frequency increases above
3.5 MHz are
also irrelevant.
Walt, W2DU
============================================

Dear Walt,

At risk of upsetting a great number of patriotic USA citizens, all BLE
hero-worshippers, I admit to having speed-read BLE's lengthy paper
some years back. Their conclusion, that with a sufficiant number and
length of radials the ground characteristics are irrelevant, is so
glaringly apparent they could have stayed in their offices and saved a
great deal of expense and copper wire. I am reminded of John Cleese's
remark "They must have had first-class honors degrees in stating the
bleeding obvious".

Because BL&E omitted to measure ground conductivity and permittivity
on the site their conclusion amounted to making a virtue out of a vice
and Marzipan the Magician's magic number of 120 came into existence.
Their sponsors should have made them go back to finish the job.

In the absence of any other information at the time, the fact of
irrelevance was of interest to LF and MF broadcasters with money to
burn, but it was, and still is, of no use to radio amateurs, confined
to the HF bands with limited purses, small back yards and XYL's to
keep happy.

My small program Radial_3 has been singled out and I have been accused
of disagreeing in a disruptive, almost criminal manner with BL&E's
conclusions. This is patently untrue! The program has nothing to do
with BL&E except that it deals with a similar subject in terms
appropriate to amateurs and draws its own independent conclusions.

Your absence caused a little worry. Glad to hear you were only
working.
----
Reg.

Reg, I appreciate your worry about my absence.

However, concerning the 'obviousness' of the conditions when there are enough
radials to simulate perfect ground, you must remember that it was not 'obvious'
in 1937. Prior to that time most BC 'aerials' were in the form of a 'T', a
horizontal wire (top-hat loading) supported by two towers, dangling a vertical
wire (the radiator) from the center, down to the antenna tuner. The 'ground'
system was a wire counterpoise, because very little was known about any other
type of 'ground' to work the vertical against.

Brown originated the concept of radials to improve the conductivity (meaning
reducing the resistance) of the ground, simply to avoid the construction of a
messy arrangement of wires to get tangled up in. But before presenting the
suggestion of radials to the world he proved it would work by performing the BLE
experiment.

Brown also is responsible for the tower antennas being of uniform shape over its
entire length, where before it was customary to use the diamond shape. With the
diamond shape the field strength measurements didn't follow the theory. Using
models for measurements he determined that the current on the diamond shape does
not flow uniformly, which resulted in undesirable radiation patterns. He then
demonstated that when the tower construction was of uniform cross section the
current became uniform and the radiation patterns became uniform and more
predictable and useful.

After proving the concept with models, he worked with John Leitch, chief
engineer of WCAU Philadelphia, in proving that it worked with full-size towers.
The WCAU tower was diamond shaped. The experiments with WCAU, and subsequently
with a tower of uniform cross section, proved the concept to be correct.

The result of Brown's experiment with the shape of the tower is that as of 1940,
the FCC mandated use of towers with uniform cross section for all new
installations. In addtion, no changes of any kind in the transmitting system
were permitted in stations that didn't already have a tower with uniform cross
section until the present antenna system was changed to one having uniform cross
section. Brown's influence on BC antenna systems is legendary. He also patented
the concept of using loading coils to shorten the physical length of towers.
Some towers that followed his lead have insulators between sections and an
inductance connecting them.

Brown's article, "Directional Antennas," appearing in a 1937 issue of the IRE,
formed the theoretical basis for all directional BC antennas

Brown also invented and patented the ground plane antenna for VHF and UHF. All
of his antenna experimentation was as an engineer with RCA. It was a great
experience for me to have worked in Brown's antenna lab along with guys like
Jess Epstein, O.M. Woodward, and Donald Peterson.

Walt,W2DU

Length & number of radials
 

These are very good points. I am reading these postings to try to
understand the behavior of actual implementations that lie somewhere between
the extremes you pointed out. In other words, what gets you the most bang
for the buck.... How fast does performance change with increased radial
length and number of radials.


"H. Adam Stevens, NQ5H" wrote in message
...
I'm often confronted with problems as a physicist where one can only get a
handle on upper and lower bounds.
Lower bound:
I'd say the minimum number and length of radials is 3 (must define a
plane) and 1/4 wavelength (satisfies boundary conditions).

Upper (infinite sheet of copper)
As Walt and Reg have debated, the "Cleese extreme" (to steal from Reg's
post) is trying to duplicate the "infinite perfectly conducting plane" of
our elementary physics books.
Cheers and beers
H.

73, NQ5H

Length & number of radials
 

"Reg Edwards" wrote in message
...

"H. Adam Stevens, NQ5H" wrote
I'm often confronted with problems as a physicist where one can only
get a
handle on upper and lower bounds.
Lower bound:
I'd say the minimum number and length of radials is 3 (must define a
plane)
and 1/4 wavelength (satisfies boundary conditions).

Upper (infinite sheet of copper)
As Walt and Reg have debated, the "Cleese extreme" (to steal from
Reg's
post) is trying to duplicate the "infinite perfectly conducting
plane" of
our elementary physics books.
Cheers and beers

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

Yes Adam, a logical way of looking at it.

Associated with any number there is always another number which is
sometimes, but not often enough, used to describe its uncertainty.

But nearly always it takes much longer to determine the uncertainty
than it does to arrive at the first number, especially if the first
number is the result of a measurement.
----
Reg.



That got a chuckle.
I'm an EXPERIMENTAL physicist.
;^)

Length & number of radials
 

Depends.
You could just keep adding radials when you can afford more copper until
things stop improving.
(Whatever "stop improving" means to you.)
Copper's expensive.

My SteppIR vertical is on an aluminum roof.
(Just my approach to the problem)

And Walt's right.
What is trivially obvious to us wasn't so in 1937.
Maxwell's equations weren't 100 years old yet.
It had only been a few years since Gibbs wrote them in the modern form we
use.
Radio was barely understood by only a few people.

73
H.

NQ5H
"Wayne" wrote in message
news:L0Nwg.5924$yN3.4270@trnddc04...
These are very good points. I am reading these postings to try to
understand the behavior of actual implementations that lie somewhere
between the extremes you pointed out. In other words, what gets you the
most bang for the buck.... How fast does performance change with
increased radial length and number of radials.


"H. Adam Stevens, NQ5H" wrote in message
...
I'm often confronted with problems as a physicist where one can only get
a handle on upper and lower bounds.
Lower bound:
I'd say the minimum number and length of radials is 3 (must define a
plane) and 1/4 wavelength (satisfies boundary conditions).

Upper (infinite sheet of copper)
As Walt and Reg have debated, the "Cleese extreme" (to steal from Reg's
post) is trying to duplicate the "infinite perfectly conducting plane" of
our elementary physics books.
Cheers and beers
H.

73, NQ5H

Length & number of radials
 

On Sun, 23 Jul 2006 11:35:42 -0500, "H. Adam Stevens, NQ5H"
wrote:

Depends.
You could just keep adding radials when you can afford more copper until
things stop improving.
(Whatever "stop improving" means to you.)
Copper's expensive.

My SteppIR vertical is on an aluminum roof.
(Just my approach to the problem)

And Walt's right.
What is trivially obvious to us wasn't so in 1937.
Maxwell's equations weren't 100 years old yet.
It had only been a few years since Gibbs wrote them in the modern form we
use.
Radio was barely understood by only a few people.


Hi OM,

In fact, how "many" people knew is immaterial to what was known a good
twenty five years before the BLE paper.

From my "Standard Handbook for Electrical Engineers," 1912,
Sec. 21, Radiotelegraphy, Method of Exciting the Antenna, part 283
Antenna Ground Connections:
"The outward and inward movement of the lines of electric force
during the oscillations in the antenna give rise to earth
currents. These earth currents are most intense in the immediate
neighborhood of the antenna, and if the earth is a poor conductor
a large waste of energy ensues. To guard against this loss, a
radiating network of wire is place beneath and around the antenna.
In the case of a flat-top antenna, the radius of this wire net
should not be less than the length of the horizontal portion of
the antenna."

I shouldn't have to point out that a handbook is not the place where
new science appears, but where tested science is aggregated. Earth
currents, screens, and lost power were not unfamiliar a century ago.

What is "Bleeding obvious" about the BLE paper, is that it puts
numbers to the quoted paragraph above in the face of its mocking:
At risk of upsetting a great number of patriotic USA citizens, all BLE
hero-worshippers
It is quite evident that the merit of the BLE paper serves the true
spirit of Lord Kelvin, and that in the context of this group, it is
USA citizens who honor his precepts in the face of this last piece of
British trolling of Reggie's who is more interested in juvenile
posturing than celebrating his heritage's expression in a fine work.

73's
Richard Clark, KB7QHC

Length & number of radials
 

Reg Edwards wrote:
"H. Adam Stevens, NQ5H" wrote

I'm often confronted with problems as a physicist where one can only

get a

handle on upper and lower bounds.
Lower bound:
I'd say the minimum number and length of radials is 3 (must define a

plane)

and 1/4 wavelength (satisfies boundary conditions).

Upper (infinite sheet of copper)
As Walt and Reg have debated, the "Cleese extreme" (to steal from

Reg's

post) is trying to duplicate the "infinite perfectly conducting

plane" of

our elementary physics books.
Cheers and beers


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

Yes Adam, a logical way of looking at it.

Associated with any number there is always another number which is
sometimes, but not often enough, used to describe its uncertainty.

But nearly always it takes much longer to determine the uncertainty
than it does to arrive at the first number, especially if the first
number is the result of a measurement.
----
Reg.



What is the uncertainty of the uncertainty? If the uncertainty is a
number, then, "Associated with any number there is always another
number which is sometimes, but not often enough, used to describe its
uncertainty." You're going to end up with an infinite string of
uncertainties if you keep this up, Reg.
73,
Tom Donaly, KA6RUH (Who never could understand Sartre.)

Length & number of radials
 

"Wayne" wrote
understand the behavior of actual implementations that lie somewhere
between
the extremes you pointed out. In other words, what gets you the
most bang
for the buck.... How fast does performance change with increased
radial
length and number of radials.
===================================

That's exactly what program RADIAL_3 is intended to help you with.

All the user has to do is convert radiating efficiency into bucks. The
higher the radiating efficiency the more bucks it will cost, the
greater the length of wire, and the more painful the back ache.

It's a matter of diminishing returns.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

Length & number of radials
 

"Reg Edwards" wrote in message
...

"Wayne" wrote
understand the behavior of actual implementations that lie somewhere
between
the extremes you pointed out. In other words, what gets you the
most bang
for the buck.... How fast does performance change with increased
radial
length and number of radials.
===================================

That's exactly what program RADIAL_3 is intended to help you with.

All the user has to do is convert radiating efficiency into bucks. The
higher the radiating efficiency the more bucks it will cost, the
greater the length of wire, and the more painful the back ache.

It's a matter of diminishing returns.
----
.................................................. .........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. .........



So if you calculate it in Pounds, is the back ache worse?
;^)

73
H.

Length & number of radials
 

Thanks Richard...however the info you present doesn't deal with the real
issue that has been raised by Reg's program: (you are adressing another area
of possible disagreement)

Do 26 radials 5 metres long perform substantially as well as 26 radials 16
metres long at 3.62 mhz with the two soil constants = 25 (in my case), with
radial wire size #14 and antenna wire size #10 (I think I used 2mm and 4mm
in my calculations.)

The issue has never been (for me) how closely does Reg's program match a 1/4
wave vertical with standard length radials. The "real" question is does
Reg's program accurately reflect the performance of vastly shorter radials
than the typical "wives' tale" (Reg's characterization) 1/4 wave length
radials.

I have always accepted that some shortening of earth based (on or under)
radials (below the assumed 1/4 w or longer as in BL&E) was acceptable. The
problem is, Reg's program allows incredible shortening, predicting high
efficiency at the same time.

I have a 1000' of wire left to put down. If Reg is right, I can put down 66
radials 5 metres long and get outstanding surface coverage. If more
"orthodox" texts are correct, then I should stick with 16 metre (approx 50')
length and then I can only put down 20 more radials than the 26 I have now.

Let's not get distracted (although your point for the 20 degree antenna
shows yet another departure from BL&E).

Here's the fundamental contradiction between Reg's program and the orthodox
approaches:

================================================
Reg says (given the values I have stated above), that 5 metre long radials
will peform (substantially) as well as 16 metre long radials, all other
things being equal. Thinking this makes my head hurt.
================================================

BL&E seems to contradict this (although I haven't found the precise
comparison I'm looking for yet).

Tom, W8JI's, measurements seem to contradict this.

NEC-4 should be able to tell us how much current is in a radial and how that
current is distributed along the length of the wire. If it disappears into
inconsequential levels within the first 5 metres, then it confirms Reg's
assertion. If it does not, i.e., it remains at substantive levels well
beyond 5 metres, then it contradicts Reg's program, and agrees with BL&E, as
well as W8JI. (I thought NEC-4 could do this problem, maybe my assumption is
completely wrong.)

================================================== ============
If NEC-4 can't do this "current along a radial" analysis (buried or on the
surface, take your pick), then we need experimental data that shows us the
same thing: how fast does the current along a radial decrease to
inconsequential levels. If it is within the first 5 metres, Reg is right. If
not, he's wrong. It's as simple as that.
================================================== =============
Why is it so hard to get this answer?

hasan, N0AN


"Richard Fry" wrote in message
...
"Reg Edwards" wrote
"Richard Fry" wrote
N. B. for/to REG EDWARDS (G4FQP): I hope that you will be
motivated to follow through on one or the other of these offers,
and that you will post a comparison of the results of your
ready-to-run, "radial_3" DOS program as compared to the
BL&E datum, for equivalent conditions.
= = =
What equivalent conditions? Where can they be found? What was the
ground resistivity and permittivity on BL&E's site?

I am not motivated to do anything except reply to your remarks.
...
Reg.
_______________

OK, I'll do it then. Attached is a plot of BL&E's numbers versus yours,
for
the conditions stated there. Ground resistivity and permittivity were
estimated using the FCC's M-3 chart to select values of R and K at the
BL&E
test site from those shown in your program.

Other parameters for radial_3 calculations were taken from the physical
and
electrical descriptions in the BL&E paper. The OD and depth of the
radials
were estimated.

You and BL&E agree fairly well for a 90 degree vertical, but not well at
all
for a 20 degree vertical.

I'll be glad to explain how I generated my plots, and even send you the
spreadsheet, if you want.

RF

Length & number of radials
 

"hasan schiers" wrote ...
Do 26 radials 5 metres long perform substantially as well as
26 radials 16 metres long at 3.62 mhz with the two soil
constants = 25 (in my case), with radial wire size #14 and
antenna wire size #10 (I think I used 2mm and 4mm in my calculations.)

Some insight into this is provided by the following.

Figure 37 in the BL&E paper shows about 77.5% of the theoretical maximum
inverse field for a 77 degree vertical used with 30 radials of
0.137-wavelength each.

Figure 36 shows 90.6% of the theoretical maximum inverse field for the same
vertical with 30 radials of 0.411-wavelength.

For 30 each 0.137-wavelength radials and a 77 degree vertical, Reg's program
radial_3 calculates an efficiency corresponding to 87.2% of the theoretical
maximum inverse field. (Other parameters for radial_3 were as shown in the
plots I posted earlier.) This is significant when considering that the
inverse field varies by the square root of this power difference.

NEC-4 should be able to tell us how much current is in a radial
and how that current is distributed along the length of the wire. If it
disappears into inconsequential levels within the first 5 metres,
then it confirms Reg's assertion. If it does not, i.e., it remains at
substantive levels well beyond 5 metres, then it contradicts Reg's
program, and agrees with BL&E, as well as W8JI.

BL&E data show that if few radials are used they may as well be "short,"
because system performance isn't improved greatly by making them much
longer. Quoting the BL&E paper (p.760), "These diagrams show that the
ground system consisting of only 15 radial wires need not be more than 0.1
wave length long, while the system consisting of 113 radials is still
effective out to 0.5 wave length.

But there was no experimental evidence from BL&E showing that radiation
efficiency ever _improved_ with shorter radials, as apparently calculated by
radials_3..

RF

Length & number of radials
 

Wayne,

The best study I've seen is in both the ARRL Antenna Handbook and in ON4UN's
Low Band DX'ing Handbook. I think it was a 3 station that came up with a
method (consistent with BL&E) that gave a simple formula for putting down
the optimum number and length of radials, for a given length of radial wire
available. I used that study to originally arrive at 50' long radials at
80m. This gave tip to tip separation of about 3 or 4 feet on 80m, which met
his criteria. The material above specifically answers the question: how do
you get the best bang for the buck for a given amount of available radial
wire.

Read that material..or at least get the formula and apply it to your
available wire...that will get you were most of us are with respect to
optimizing radials.

Now, Reg has come up with his program that flies in the face of these other
studies, indicating one can obtain comparable performance with MUCH shorter
radials (5 metres instead of 16 metres) and that is what started this whole
thread. We await some sort of comfirmation from several sources that Reg's
numbers are correct. If they are, Reg will become famous.

Currently here is how things line up:

1. BL&E doesn't seem to agree with Reg's numbers (on the issue of short
radials)
2. Tom, W8JI's, recollection of his measurement don't either.
3. NEC-4 is in the process of analyzing the short radial comparability claim
as we speak.

The entire issue is: does the current in the radials described above taper
off as quickly as Reg predicts, or not? If it does, the short radials will
be comparable and Reg is right. If it doesn't, Reg needs to fix his program
in that particular section.

We await more data, or someone to extract from BL&E a precise answer to the
actual question: how fast does current fall in a radial as you move away
from the base of a 1/4 wave ground mounted vertical with shallowly buried
radials.

In the mean time, you can get started with the formula I referred to above.
If Reg is right, you used more wire than needed. If not, you have your wire
in place and are ready to go.

....hasan, N0AN
"Wayne" wrote in message
news:L0Nwg.5924$yN3.4270@trnddc04...
These are very good points. I am reading these postings to try to
understand the behavior of actual implementations that lie somewhere
between the extremes you pointed out. In other words, what gets you the
most bang for the buck.... How fast does performance change with
increased radial length and number of radials.

Length & number of radials
 

On Mon, 24 Jul 2006 08:32:08 -0500, "hasan schiers"
wrote:

The best study I've seen is in both the ARRL Antenna Handbook and in ON4UN's
Low Band DX'ing Handbook. I think it was a 3 station that came up with a
method (consistent with BL&E) that gave a simple formula for putting down
the optimum number and length of radials, for a given length of radial wire
available. I used that study to originally arrive at 50' long radials at
80m. This gave tip to tip separation of about 3 or 4 feet on 80m, which met
his criteria. The material above specifically answers the question: how do
you get the best bang for the buck for a given amount of available radial
wire.

You can find the article and the formula in the August 2004 QST.

Danny, K6MHE

Length & number of radials
 

On Mon, 24 Jul 2006 08:47:36 -0700, Dan Richardson
wrote:

You can find the article and the formula in the August 2004 QST.


OOOPS! Make that August 2003!

Sorry,

Danny, K6MHE