Cecil Moore wrote:

Assume a one second long lossless unterminated transmission line.
Pour 1000 watts into it for one second. During the next second, we
disconnect the line from the source and you grab the two wires, one
in each hand. Then tell us whether reflected power exists or not.


So if we had an infinitely long antenna, would the power put into it
last forever?

- Mike KB3EIA -

Mike Coslo wrote:

Cecil Moore wrote:

Assume a one second long lossless unterminated transmission line.
Pour 1000 watts into it for one second. During the next second, we
disconnect the line from the source and you grab the two wires, one
in each hand. Then tell us whether reflected power exists or not.

So if we had an infinitely long antenna, would the power put into it
last forever?

It would have a feedpoint impedance of around 600 ohms and I
don't know how long it would have to be to eliminate reflections.
A terminated rhombic comes close to the characteristics of an
infinitely long antenna.
--
73, Cecil http://www.qsl.net/w5dxp



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Richard Clark wrote:
There are both wave descriptions of this process, and lumped circuit
equivalents. Both work, and both describe the same process from
different points of view. One does not negate the other's validity

I agree with that last statement - and we can take it a step further.

Each description can do things that the other one can't; no argument
about that. But in cases where both descriptions should be valid, then
they *must* agree.

This is a basic cross-check that should always be applied... but
regrettably isn't.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

On Sun, 23 May 2004 09:31:10 +0100, "Ian White, G3SEK"
wrote:

This is a basic cross-check that should always be applied... but
regrettably isn't.

Hi Ian,

Perhaps in this immediate thread. However, I have demonstrated both
sides coming to the same conclusions several many times, and one
example as recently as within this last week.

This issue is not about being right, it is about ego foremost else why
all the debate? Hank has asked a fairly straightforward question
with rather simple terms he could accept as a compelling case. To
this point (some 22 entries) that has been largely abandoned with each
scribbler answering their own imagining of how to discover the
philosopher's stone.

73's
Richard Clark, KB7QHC

Richard Clark wrote:

Hi Ian,

Perhaps in this immediate thread. However, I have demonstrated both
sides coming to the same conclusions several many times, and one
example as recently as within this last week.

This issue is not about being right, it is about ego foremost else why
all the debate? Hank has asked a fairly straightforward question
with rather simple terms he could accept as a compelling case. To
this point (some 22 entries) that has been largely abandoned with each
scribbler answering their own imagining of how to discover the
philosopher's stone.

73's
Richard Clark, KB7QHC

I haven't been here terribly long, maybe 6 weeks, but I have noticed
that your comment applies to around half of the threads longer than 4 or
so comments.

A better ratio than many newsgroups, and people seem to have a sense of
humor, which a lot of other newsgroup's participants decidedly do not.
So, all in all, it could be worse.

tom
K0TAR

Tom Ring wrote:

Richard Clark wrote:

Hi Ian,

Perhaps in this immediate thread. However, I have demonstrated both
sides coming to the same conclusions several many times, and one
example as recently as within this last week.

This issue is not about being right, it is about ego foremost else why
all the debate? Hank has asked a fairly straightforward question
with rather simple terms he could accept as a compelling case. To
this point (some 22 entries) that has been largely abandoned with each
scribbler answering their own imagining of how to discover the
philosopher's stone.

73's
Richard Clark, KB7QHC


I haven't been here terribly long, maybe 6 weeks, but I have noticed
that your comment applies to around half of the threads longer than 4 or
so comments.

A better ratio than many newsgroups, and people seem to have a sense of
humor, which a lot of other newsgroup's participants decidedly do not.
So, all in all, it could be worse.

That's very true, Tom. Even with the egos, the civility level is
pretty high in here. Of course that is probably why the fringe elements
don't hang out here.

- Mike KB3EIA -

Richard Clark wrote:
As for the math, you will find it by
the reams, once you've been overwhelmed with the arcana of hyperbolic
descriptions of a novel physics that have to proceed its proof.

A scattering parameter analysis, described in HP Application Note
95-1 (available on the web) is ideal for analyzing what happens
at a match point in a typical ham radio antenna system.

b1 = s11(a1) + s12(a2)

b2 = s21(a1) + s22(a2)

b1 is the net forward voltage, b2 is the net reflected voltage
a1 is the incident forward voltage, a2 is the incident reflected voltage

Quoting from HP AN 95-1: Another advantage of s-parameters springs
from the simple relationship between the variables a1, a2, b1, and
b2, and various power waves:

|a1|^2 = Power incident on the input of the network.
(forward power incident on the match point)

|a2|^2 = Power reflected from the load.

|b1|^2 = Power reflected from the input port of the network.
(power reflected from the match point back toward the source)

|b2|^2 = Power incident on the load.

The previous four equations show that s-parameters are simply
related to power gain and mismatch loss, quantities which are
often of more interest than the corresponding voltage functions.

|s11|^2 = Power reflected from the network input divided by
power incident on the network input

|s22|^2 = Power reflected from the network output divided by
power incident on the network output

|s21|^2 = Power delivered to a Z0 load divided by power available
from a Z0 source

|s12|^2 = Reverse transducer power gain with Z0 load and source

End quote.

b2 is the voltage reflected back toward the source and

b2 = s21(a1) + s22(a2)

It should be obvious that b2 cannot be zero unless there exists
total destructive interference between s21(a1) and s22(a2), i.e.
s21(a1) is equal in magnitude and opposite in phase to s22(a2).
--
73, Cecil http://www.qsl.net/w5dxp



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On Sun, 23 May 2004 10:06:15 -0500, Cecil Moore
wrote:

Richard Clark wrote:
As for the math, you will find it by
the reams, once you've been overwhelmed with the arcana of hyperbolic
descriptions of a novel physics that have to proceed its proof.

A scattering parameter analysis,...
arcana deleted as an obviously fulfilled prophecy.

Richard Clark wrote:

wrote:
A scattering parameter analysis,...

arcana deleted as an obviously fulfilled prophecy.

Richard, you are the only technical person I know of who
ever considered s-paramater analysis to be a secret or
mystery. It is one of the more technically popular methods
of analysis, ideally suited to transmission line analysis.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil Moore wrote:

Richard Clark wrote:

As for the math, you will find it by
the reams, once you've been overwhelmed with the arcana of hyperbolic
descriptions of a novel physics that have to proceed its proof.


A scattering parameter analysis, described in HP Application Note
95-1 (available on the web) is ideal for analyzing what happens
at a match point in a typical ham radio antenna system.

b1 = s11(a1) + s12(a2)

b2 = s21(a1) + s22(a2)

b1 is the net forward voltage, b2 is the net reflected voltage
a1 is the incident forward voltage, a2 is the incident reflected voltage

Quoting from HP AN 95-1: Another advantage of s-parameters springs
from the simple relationship between the variables a1, a2, b1, and
b2, and various power waves:

|a1|^2 = Power incident on the input of the network.
(forward power incident on the match point)

|a2|^2 = Power reflected from the load.

|b1|^2 = Power reflected from the input port of the network.
(power reflected from the match point back toward the source)

|b2|^2 = Power incident on the load.

The previous four equations show that s-parameters are simply
related to power gain and mismatch loss, quantities which are
often of more interest than the corresponding voltage functions.

|s11|^2 = Power reflected from the network input divided by
power incident on the network input

|s22|^2 = Power reflected from the network output divided by
power incident on the network output

|s21|^2 = Power delivered to a Z0 load divided by power available
from a Z0 source

|s12|^2 = Reverse transducer power gain with Z0 load and source

End quote.

b2 is the voltage reflected back toward the source and

b2 = s21(a1) + s22(a2)

It should be obvious that b2 cannot be zero unless there exists
total destructive interference between s21(a1) and s22(a2), i.e.
s21(a1) is equal in magnitude and opposite in phase to s22(a2).
--
73, Cecil http://www.qsl.net/w5dxp

Richard is right, There is the first ream!

Sorry, I'm a bit pippish today..........

- Mike KB3EIA -