"Richard Clark" wrote in message
...
On Fri, 05 Nov 2004 13:57:16 -0600, Cecil Moore
wrote:
The combined effort to suppers the ideas of Kraus and Balanis is getting
Darn spellchecker. "suppers" should be "suppress".
more ridiculous with each passing day. It can no longer be explained by
ignorance.
Blame the spellchecker?

C'mon, Richard. That's a cheap shot beneath even you, I thought.

"Richard Clark" wrote in message
...
On Fri, 05 Nov 2004 07:45:16 GMT, Richard Clark
wrote:

So much for theories of Rr being modified by loading. I would
appreciate other effort in kind to correct any oversights I've made

Hi All,

Nothing to offer? I didn't think so. :-)

Well, to enlarge the dialogue (but still reject those who prefer to
change the topic to what they CAN prove), any -ahem- "explanations?"

73's
Richard Clark, KB7QHC



Did you say something, Richard?

"Richard Clark" wrote in message
news
On Fri, 05 Nov 2004 10:45:57 -0800, Jim Kelley
wrote:

I have a question. Can you express the mathematical and/or physical
relationship between Rr and antenna gain? It would sure help to clarify
the point you were trying to make.

Hi Jim,

I would have thought someone else could, given the bandwidth of
discussion in making the current taper shorter and the constant
current section longer. Testing does not bear their facile
relationship out however, and for the topic of a short antenna
(otherwise, why are we talking about loading coils?) it would seem
that antenna gain is immutable over several octaves below a
quarterwave length.

Of course, I coulda done something wrong. I did use a commonly
available design. I did use a commonly available modeler. I even may
have done the wrong thing in choosing a design that could be evaluated
for free. Perhaps I erred in providing the cogent details of
construction. It took all of 20 minutes to accomplish (far less time
than that expended in theories of current-in/current-out). These
technical hurdles appear to have set the bar too high for my work's
refutation in kind. I appreciate that "it's hard work!" ;-)

To answer your question, if you just abandon the perfect load, then
you stand to achieve a higher gain. If you shorten the antenna, then
you stand to achieve a higher gain. There is no change in Rr with the
addition of Xl. Hence the mathematical relationship for an antenna
shorter than quarterwave would be suggested as:
gain ~ 1/Rr
gain ~ 1/Xl
Rr Z

Don't take this gain to the bank however.

73's
Richard Clark, KB7QHC



Oh... This is about gain? No wonder I'm confused about the subject.

"Roy Lewallen" wrote in message
...
I'm sorry, but I can't make any sense out of your response, so I'm unable
to answer your question.

Roy Lewallen, W7EL


Richard does that a lot, doesn't he?


Richard Clark wrote:

On Fri, 05 Nov 2004 13:06:40 -0800, Roy Lewallen
wrote:


What makes you think that the Rr isn't changing?


Hi Roy,

With what?

I have offered a very ascetic report of very simple actions from very
simple terms. You have chosen to change those terms to fit your own
answer (I do not choose to put this into the context of a perfect
world). Please offer effort in kind, or point out what error I've
made instead of what error I might have made if something were changed
from my model.

73's
Richard Clark, KB7QHC

On Sat, 06 Nov 2004 02:34:32 GMT, "Frank"
wrote:

Regarding Richard's comments "Assuming the same currents". Not sure I
understand, since the feed-point current varies with constant power

Hi Frank,

That is quite simple. The file VERT1.EZ has as a source, a constant
current generator - a fact I pointed out in the summary of my results.
Your presumption of constant power is a natural one for the sake of
common discussion, but it is not even the default source for EZNEC.

[However, having said that, a curiosity of program design has found
that the concept of a "new file" has been orphaned. Any time the
application is opened, it is opened with LAST.EZ and I cannot recall
upon initial acquisition if EZNEC ever started with a blank slate.
Given that you cannot have less than 1 wire nor 1 source, then there
is on way to force a blank file. Hence the concept of a default
resides in the last file opened.]

In other words, each and every iteration of antenna, irrespective of
its presumed or actual Rr or drivepoint Z had the same current applied
to it, 1 Ampere.

Now, if ANY resistance had changed, it then follows that the POWER
would have changed too (which presents us with that puzzle
confused by the expression V=I/R.
that came out of the blue) at a linear rate (1² = 1).

Note, a doubling of drivepoint Z by the addition of a load does not
result in 3dB gain over the former design. I have seen I * I * R
bandied about as an "explanation" and yet at least 3dB is remarkably
absent in the results. What R is this that everyone speaks of?
Certainly not the real component of drivepoint Z. What about the Rr
that must've changed? Copper loss absorb it? Ground loss?

As I offered, I must've done something wrong, taken the wrong turn,
interpreted the modeler in error, -ahem- not read the help file....

I will bet it was that last one - which only reveals no one has. ;-)

[aside]
So, Wes, I will amend my ways and delve into that treasure of
knowledge before returning your work in kind (no point in retread
effort) sometime tomorrow morning.

[to the audience]
C'mon folks, this has to be an especially simple resolution - I'm glad
that so many are just as flummoxed (even Reg is uncharacteristically
silent in this regard :-)

73's
Richard Clark, KB7QHC

On Fri, 5 Nov 2004 22:06:42 -0600, "John Smith"
wrote:
C'mon, Richard. That's a cheap shot beneath even you, I thought.

Hi John,

Your exposure to cheap shots is clearly shallow. ;-)

73's
Richard Clark, KB7QHC

I'd be glad to help clarify any confusion, but I can't for the life of
me figure out what the confusion is about.

Regarding EZNEC's sources, you have the option of using a
constant-current source, constant-voltage source, or having a fixed
power applied to the model. If a fixed power level is chosen, multiple
sources will have the same ratio of voltages and currents as you've
specified. For example, if your model has two sources, one of 1 amp and
the other 2 amps, and you choose a fixed power level, the current from
the second source will always be twice the current from the first (and
at the specified relative phase), but both will be modified as necessary
to produce the total power you specified.

Fixed power is selected in the Options menu. While the relative source
currents (2 amps and 1 amp in the example) are saved with the model, the
Options menu choices aren't. They're applied to all models. Changes you
make in the Options menu remain effective until you end the program. If
you choose "Save as Default" from the Options menu, the current settings
will remain in effect even after you end the program, until you change them.

I don't personally use a fixed power level very often, since I'm more
often interested in things like currents on wires relative to a source,
so it's convenient for me to set the source to 1 amp. The fixed power
level is useful whenever you need an absolute value of voltage or
current, though, or want to see how the voltage, current, or load power
dissipation changes as you modify the model. It can be helpful in
understanding radiation resistance, by illustrating the relationship
among feepoint power, current, and resistance.

Just what is it that's confusing about radiation resistance and EZNEC
results? Richard's EZNEC results are exactly what I'd expect, and
they're consistent with theory. (I'm talking about established theory
found in textbooks, not ones cooked up by people who don't understand
basic principles or common nomenclature.) The small gain change due to
the ground reflection reaction to altered current distribution was
admittedly a surprise, but it makes perfect sense after a moment's
thought. If someone can summarize what seems to be wrong, I'll do my
honest best to explain it. Is the problem that the gain doesn't go up
with Rr? Of course it doesn't, in the nearly lossless antennas of
Richard's models. Why should it? I tried to explain why in my earlier
posting, but I'll try again if that's what the problem is.

Roy Lewallen, W7EL

Richard Clark wrote:

On Sat, 06 Nov 2004 02:34:32 GMT, "Frank"
wrote:


Regarding Richard's comments "Assuming the same currents". Not sure I
understand, since the feed-point current varies with constant power


Hi Frank,

That is quite simple. The file VERT1.EZ has as a source, a constant
current generator - a fact I pointed out in the summary of my results.
Your presumption of constant power is a natural one for the sake of
common discussion, but it is not even the default source for EZNEC.

[However, having said that, a curiosity of program design has found
that the concept of a "new file" has been orphaned. Any time the
application is opened, it is opened with LAST.EZ and I cannot recall
upon initial acquisition if EZNEC ever started with a blank slate.
Given that you cannot have less than 1 wire nor 1 source, then there
is on way to force a blank file. Hence the concept of a default
resides in the last file opened.]

In other words, each and every iteration of antenna, irrespective of
its presumed or actual Rr or drivepoint Z had the same current applied
to it, 1 Ampere.

Now, if ANY resistance had changed, it then follows that the POWER
would have changed too (which presents us with that puzzle

confused by the expression V=I/R.

that came out of the blue) at a linear rate (1² = 1).

Note, a doubling of drivepoint Z by the addition of a load does not
result in 3dB gain over the former design. I have seen I * I * R
bandied about as an "explanation" and yet at least 3dB is remarkably
absent in the results. What R is this that everyone speaks of?
Certainly not the real component of drivepoint Z. What about the Rr
that must've changed? Copper loss absorb it? Ground loss?

As I offered, I must've done something wrong, taken the wrong turn,
interpreted the modeler in error, -ahem- not read the help file....

I will bet it was that last one - which only reveals no one has. ;-)

[aside]
So, Wes, I will amend my ways and delve into that treasure of
knowledge before returning your work in kind (no point in retread
effort) sometime tomorrow morning.

[to the audience]
C'mon folks, this has to be an especially simple resolution - I'm glad
that so many are just as flummoxed (even Reg is uncharacteristically
silent in this regard :-)

73's
Richard Clark, KB7QHC

On Thu, 4 Nov 2004 08:08:00 -0600, (Richard
Harrison) wrote:

|Wes, N7WS wrote:
|"Could you describe in more detail what the "pictures" are saying."
|
|My edition of "Low-Band DXing" is copyrighted in 1994.
|
|The "pictures" are graphs of current distribution on (6) different
|1/4-wave vertical antennas:
|1) full size
|2) base loaded 1/8-wave of wire
|3) capacitive hat loaded 1/8-wave
|4) center loaded 1/16-wave wire above & below
|5) continuously loaded (all coil) antenna
|6) combined top and base loading of short vertical

Okay, I guessed correctly. This is fig. 9-40 in the third edition.
|
|The current distribution graphs are in a section (2.1) titled
|"Radiation Resistance"

Figure 9-44
|
|In every case , the current tapers lower from feedpoint end to the
|loading coil`s end nearer the open end of the antenna. Devoldere
|discusses the various loading methods.

Yes, but as I mentioned in my analysis at:

http://www.qsl.net/n7ws/Loaded%20antennas.htm

for the extremely short antennas that were (are) the subject of the
"shootout" business, the current actually increases between the ends
of the inductor.

Richard Clark wrote:
Cecil Moore wrote:
Darn spellchecker. "suppers" should be "suppress".

Blame the spellchecker?

Yep, it changed "supress" to "suppers".
--
73, Cecil http://www.qsl.net/w5dxp


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John Smith wrote:
"Oh...This is about gain?"

Don`t think so. This is about unequal currents into and out of an
antenna loading coil. The effect a loading coil has on received signals
is due at least in part to its effect on radiation resistance versus
total (radiation + loss) resistance. If you increase radiation
resistance as comared with loss resistance you increase effective
radiated power. Directive gain has nothing to do with loss.

Here is Terman`s comment on gain in Note 2 on page 870 of his 1955
edition:
"Directive gain depends entirely on the distribution in space of
radiated power. The power input to the antenna, the antenna losses, or
the power consumed in a terminating resistance have nothing to do with
directive gain. Such factors are taken into account in terms of the
power gain of the antenna which is defined as the ratio of the power
input to the comparison antenna required to develop a particular field
strength in the direction of maximum radiation, to the power input that
must be delivered to the directional antenna to obtain the same field
strength in the same direction. Unless otherwise specified the
comparison antenna is a lossless isotropic radiator."

Best regards, Richard Harrison, KB5WZI