I asked your for the details of your antenna and measurements, and how
you did your calculations, but I am still left wondering how you have
what appears to be a purely resistive feedpoint impedance and a radiation
resistance of 4 ohms. The second implies a short vertical, and if that is
the case, the first implies some form of loading... but you didn't
mention loading of any kind. Loading, if you have used it, may introduce
an equivalent series resistance at the feedpoint.

Once again, a dansawyer problems leaves us guessing to fill in the
missing dots before attempting to joint them up to make a picture.

Often, solving a problem is about being able to draw the picture, once
the picture is draw, the answer becomes trivial.

Owen

I was also confused by the base of the antenna being 1 meter above
ground, and the radials lying on the ground, or buried. If the base
of the antenna is 1 meter high, then any connection to the radials
is part of the radiation system. Why would you feed the antenna
1 meter up, and not at the base? The antenna is therefore
a ground mounted 5 meter vertical.

NEC predicts an input impedance of 4 - j 1300 with 36 ten meter
radials 1" below an average ground. Loading coils will of course
add to the input impedance.

The measured data are suspect. It would be interesting to know
the length, and type, of coax connecting to the network analyzer.
The return loss of 25 ohms at the end of a piece of coax will be
9.5 dB. Unless the coax is cut to a precise known length it
is unlikely that the phase angle of the return loss will be zero.


Frank.

On Mon, 09 Apr 2007 13:27:21 -0700, Roy Lewallen
wrote:

So, does the current go clockwise or counterclockwise? How much goes
that way compared to the radial component? Where can I find a
quantitative or explicit statement of your interpretation?

Hi Roy,

Probably in a library. Field work seems to resolve issues too. It
may even prove your speculation in contradiction to mine. Outside of
these authors, we both seem to be shy of "authoritative references" to
parse that Byzantine statement of theirs.

I can only further speculate that BL&H were remiss in specifically
quantifying loss (you aren't asking me for numbers you are already
aware of, are you?), while offering numerous formulaic relationships
of loss against many factors. If we look at their data and observe
that adding radials lowers loss, but not by any precise relationship,
are we left without quantifiable proof, or the obvious implication of
strong correlation? Was there deceit in their arriving at some
conclusions through inference? As Reggie would note, they didn't
actually measure earth at all! Such a retort was met with indignity
in the past, is it now their impeachment?

However, as to counter/anti/clockwise, What impels current to follow
any such presumption? There are two sides to every wire laying in a
plane and phase mappings for earth currents that are symmetrical about
them. To anticipate your challenging me on that statement (clearly
BL&H never, explicitly say this), I can only offer a modest sense of
observing the bleeding obvious. Myself, I don't find BL&H so obscure
to impose this remarkable characteristic that current leaves the wire
on only one side.

Brown, Lewis and Epstein were REPORTING, not inventing, nor offering
pedant readings of scripture. Scribes, such as we are, are free to
interpret within the bounds of their own data, assumptions, and
conclusions. I've offered mine that conforms to many of their points.
If you have your own, you must survive by the same strictures. Given
the specific contention, I am especially intrigued in how you would
answer why the current departed the wire, and where it goes in light
of a potential map created by the phase shifts.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Mon, 09 Apr 2007 13:27:21 -0700, Roy Lewallen
wrote:

So, does the current go clockwise or counterclockwise? How much goes
that way compared to the radial component? Where can I find a
quantitative or explicit statement of your interpretation?

Hi Roy,

Probably in a library. Field work seems to resolve issues too. It
may even prove your speculation in contradiction to mine. Outside of
these authors, we both seem to be shy of "authoritative references" to
parse that Byzantine statement of theirs.

I can only further speculate that BL&H were remiss in specifically
quantifying loss (you aren't asking me for numbers you are already
aware of, are you?), while offering numerous formulaic relationships
of loss against many factors. If we look at their data and observe
that adding radials lowers loss, but not by any precise relationship,
are we left without quantifiable proof, or the obvious implication of
strong correlation? Was there deceit in their arriving at some
conclusions through inference? As Reggie would note, they didn't
actually measure earth at all! Such a retort was met with indignity
in the past, is it now their impeachment?

However, as to counter/anti/clockwise, What impels current to follow
any such presumption? There are two sides to every wire laying in a
plane and phase mappings for earth currents that are symmetrical about
them. To anticipate your challenging me on that statement (clearly
BL&H never, explicitly say this), I can only offer a modest sense of
observing the bleeding obvious. Myself, I don't find BL&H so obscure
to impose this remarkable characteristic that current leaves the wire
on only one side.

Brown, Lewis and Epstein were REPORTING, not inventing, nor offering
pedant readings of scripture. Scribes, such as we are, are free to
interpret within the bounds of their own data, assumptions, and
conclusions. I've offered mine that conforms to many of their points.
If you have your own, you must survive by the same strictures. Given
the specific contention, I am especially intrigued in how you would
answer why the current departed the wire, and where it goes in light
of a potential map created by the phase shifts.

73's
Richard Clark, KB7QHC

Ok, I understand that. Your answers to the two questions I asked are
that you don't know and you don't know. In the absence of any evidence,
I'll continue to disbelieve there's a circumferential component of the
current.

Roy Lewallen, W7EL

Frank's wrote:
Severns' article "Verticals, Ground Systems and Some History",
July 2000, p. 39, quotes the following: "As indicated in Figure 1,
the tangential component of the H field (H(phi)) induces
horizontal currents (Ih) flowing radially and the normal
component of the E field (Ez) induces vertically flowing
currents (Iv). The paper is available for download
from www.arrl.org.

Thanks for the reference, but it makes no mention of circumferential
currents. At first glance, figure 1 seems to show a circumferential Ih,
but the text (as you quoted) clearly calls this a radial current -- the
circle in figure 1 turns out to be Hphi, circling the vertically
directed current.

Roy Lewallen, W7EL

Roy Lewallen wrote:
So, does the current go clockwise or counterclockwise? How much goes
that way compared to the radial component? Where can I find a
quantitative or explicit statement of your interpretation?

I think, based on the excerpt Richard has provided, it does both.
Imagine a leaky hose with water diffusing into the surroundings. So, if
you were to integrate over the entire width,or over any region which is
symmetric over the wire, the *net* is entirely radial, but if you look
at a small region, directly adjacent to the wire, there will be current
diverging from the wire as you move outward (assuming current flow is
outward... obviously, on the opposite half cycle, it converges toward
the wire, as it moves generally inward)...

I suspect one could also analyze it as a wave propagating away from teh
wire in the lossy surrounding medium, where the medium has a lower
propagation velocity than in the wire. (e.g. imagine a waveguide made
with the walls being soil)

Another sort of "hydraulic" model would be if you represented the
radials as below grade drainage ditches which have a lot more pitch than
the surrounding soil, so the water tends to flow diagonally down the
ditch walls.

The interesting question would be whether this is important at all..

One might go through lots and lots of analysis, worrying about the small
incremental effects of non-radial current, and find that the inherent
variations in soil properties are orders of magnitude larger.

Sounds like a good exercise for a graduate level E&M or calculus class..
you could cast it as a similar exercise in heat flow.. both temperature
and electrostatic fields satisfy Laplace's equation.

"Roy Lewallen" wrote in message
...
Frank's wrote:
Severns' article "Verticals, Ground Systems and Some History",
July 2000, p. 39, quotes the following: "As indicated in Figure 1,
the tangential component of the H field (H(phi)) induces
horizontal currents (Ih) flowing radially and the normal
component of the E field (Ez) induces vertically flowing
currents (Iv). The paper is available for download
from www.arrl.org.

Thanks for the reference, but it makes no mention of circumferential
currents. At first glance, figure 1 seems to show a circumferential Ih,
but the text (as you quoted) clearly calls this a radial current -- the
circle in figure 1 turns out to be Hphi, circling the vertically directed
current.

Roy Lewallen, W7EL

Yes, that is exactly the way I interpreted the article which is based
on the B, L, and E paper.

Frank

Richard Clark, KB7QHC wrote:
"Brown, Lewis and Epstein."

Ed Laport worked with B,L,&E at RCA. I don`t have my copy of his "Radio
Antenna Engineering" at hand, but do recall Ed`s exhortations not to
interconnect radials beyond an antenna`s drivepoint because it
encourages hysteresis (circulating) currents which do nothing to improve
antenna action but do increase loss.

All the useful ground currents at a tower are radial with respect to the
tower`s base.

Best regards, Richard Harrison, KB5WZI

Bart,

Thanks for the thought. Modeling predicts it is much lower then that;
however I don't want to overlook anything. The Q looks very good on the
network analyzer, however I have never run the math. The coil is about
3.3 inches in diameter. I will let you know.

Dan

Bart Rowlett wrote:
On Sun, 08 Apr 2007 20:20:36 -0700, dansawyeror wrote:

Owen,

I did not want to concentrate on that; however it is a fair question.
The frequency is 3970 kc and the methodology is based on use of an hp
network analyzer. The analyzer has both polar and Cartesian displays.
The outputs were cross checked.f

[snip]

To focus on the question is: Why is the ground resistance so high? It is
not important at this stage to determine its precise value. The point is
it is high enough to cause a return of 0 degrees. This puts the 'system'
at over 50 degrees. Even if the antenna were 6 to 8 Ohms the ground loss
would be at least 42 to 44 Ohms.

How is the antenna loaded and what is the Q of the loading coil? Coil
losses are almost certainly 5 ohms and could easily be as high as 35 ohms.

bart

Owen,

The antenna is a short loaded vertical. The base is about 1.1 meters
long and 90mm in diameter, the coil is about 160mm long and about 80mm
in diameter, the top is 3 meters. The coil wire is 12 gage and the
spacing is about .5. As a model cross check, the impedance of the coil
measures about 60 uH.

- Dan

Owen Duffy wrote:
Owen Duffy wrote in
:

dansawyeror wrote in
:

...

I think a summary is that at 3970KHz, the feedpoint Z looks like about
45 +j0 and you reckon the radiation resistance should be around 4+j0,
suggesting the earth system contributes around 40 ohms of resistance.
Observations at a single frequency provide a limited view of what
might be happening.

Dan,

I asked your for the details of your antenna and measurements, and how
you did your calculations, but I am still left wondering how you have
what appears to be a purely resistive feedpoint impedance and a radiation
resistance of 4 ohms. The second implies a short vertical, and if that is
the case, the first implies some form of loading... but you didn't
mention loading of any kind. Loading, if you have used it, may introduce
an equivalent series resistance at the feedpoint.

Once again, a dansawyer problems leaves us guessing to fill in the
missing dots before attempting to joint them up to make a picture.

Often, solving a problem is about being able to draw the picture, once
the picture is draw, the answer becomes trivial.

Owen

dansawyeror wrote in
:

Owen,

The antenna is a short loaded vertical. The base is about 1.1 meters
long and 90mm in diameter, the coil is about 160mm long and about 80mm
in diameter, the top is 3 meters. The coil wire is 12 gage and the
spacing is about .5. As a model cross check, the impedance of the coil
measures about 60 uH.


So, what do you think its impedance would be? 1500+j??

This is probably accounting for somewhere between 5 and 15 ohms of
additional resistance, depending on Q.

Owen