Cecil, W5DXP wrote:
"There are only two possible directions, forward and reverse in which
energy can flow. Multiple reflections do not create any more
directions."

True. Further, all the same-frequency, same-direction signals merge. So,
as Cecil said, there are only two same-frequency signals on a
transmission line, forward and reverse. The interference pattern these
signals produce does not represent another signal.

Trying to use ordinary circuit analysis on standing-wave antennas is
problematic, but it`s been tried in this thread. Here is what R.W.P.
King wrote in "Transmission Lines, Antennas, and Wave Guides", King,
Mimno, and Wing, 1945, on page 86:
"Inductance and capacitance as used in near-zone circuits with uniform
current cannot be defined, and ordinary circuit analysis does not
apply." This has not stopped efforts in this thread to analyze LC
circuits as if we were dealing with low frequencies.

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:

Cecil, W5DXP wrote:
"There are only two possible directions, forward and reverse in which
energy can flow. Multiple reflections do not create any more
directions."

True. Further, all the same-frequency, same-direction signals merge. So,
as Cecil said, there are only two same-frequency signals on a
transmission line, forward and reverse. The interference pattern these
signals produce does not represent another signal.

So the claim is that the amplitude of the reflection being bandied about
is the sum of multiple reflections? I haven't seen any indication of
that. It appears to be simply the amplitude of the first reflection.
At least, that's the way it appears to me, the uninitiated.

73, Jim AC6XG

Richard Harrison wrote:
Trying to use ordinary circuit analysis on standing-wave antennas is
problematic, but it`s been tried in this thread. Here is what R.W.P.
King wrote in "Transmission Lines, Antennas, and Wave Guides", King,
Mimno, and Wing, 1945, on page 86:
"Inductance and capacitance as used in near-zone circuits with uniform
current cannot be defined, and ordinary circuit analysis does not
apply." This has not stopped efforts in this thread to analyze LC
circuits as if we were dealing with low frequencies.

Very true. The basic problem, as I see it, is in assuming that the standing-
wave current only has one component. For standing-wave antennas, the
standing-wave current must necessarily have two components, If and Ir, as
explained by Balanis in _Antenna_Theory_, (page 489, 2nd edition).

In general, when forward waves and reflected waves exist in the circuit,
lumped circuit analysis fails and distributed network analysis is the only
method that yields the correct result. So even if one allows that the forward
current magnitude is constant through a coil and the reflected current
magnitude is constant through a coil, the net current magnitude will not
be constant because of the phase differences in the two superposed currents
at each end of the coil.

I've been told by the gurus that I can ignore the forward and reflected
waves and still obtain the correct steady-state solution. A mobile bugcatcher
coil on 75m seems to disprove that assertion. But I have been called a
"Grasshopper" and thus apparently have a lot yet to learn.
--
73, Cecil http://www.qsl.net/w5dxp



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Jim Kelley wrote:
So the claim is that the amplitude of the reflection being bandied about
is the sum of multiple reflections? I haven't seen any indication of
that. It appears to be simply the amplitude of the first reflection.
At least, that's the way it appears to me, the uninitiated.

Shirley, you jest. Reference pages 17-20 in _T-Lines & Networks_ by Johnson.
Consider a T-line with an SWR of 5.8284:1 and a constant 100W Z0-matched
source. The forward power will be 100W, 150W, 175W, 187.5W, 193.75W,
196.875W, 198.4375W, ..., 200W. After steady-state is reached, the
reflected power is a constant 100W (sans modulation and noise).
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil Moore wrote:

Jim Kelley wrote:
So the claim is that the amplitude of the reflection being bandied about
is the sum of multiple reflections? I haven't seen any indication of
that. It appears to be simply the amplitude of the first reflection.
At least, that's the way it appears to me, the uninitiated.

Shirley, you jest. Reference pages 17-20 in _T-Lines & Networks_ by Johnson.
Consider a T-line with an SWR of 5.8284:1 and a constant 100W Z0-matched
source. The forward power will be 100W, 150W, 175W, 187.5W, 193.75W,
196.875W, 198.4375W, ..., 200W. After steady-state is reached, the
reflected power is a constant 100W (sans modulation and noise).

Interesting reference. Wish I had it. He's showing re-reflections from
a Z0-matched source? I don't think I understand all I know about that.
:-)

73, AC6XG

On Tue, 18 Nov 2003 13:52:04 -0800, Jim Kelley
wrote:

|
|
|Cecil Moore wrote:
|
| Jim Kelley wrote:
| So the claim is that the amplitude of the reflection being bandied about
| is the sum of multiple reflections? I haven't seen any indication of
| that. It appears to be simply the amplitude of the first reflection.
| At least, that's the way it appears to me, the uninitiated.
|
| Shirley, you jest. Reference pages 17-20 in _T-Lines & Networks_ by Johnson.
| Consider a T-line with an SWR of 5.8284:1 and a constant 100W Z0-matched
| source. The forward power will be 100W, 150W, 175W, 187.5W, 193.75W,
| 196.875W, 198.4375W, ..., 200W. After steady-state is reached, the
| reflected power is a constant 100W (sans modulation and noise).
|
|Interesting reference. Wish I had it.

I have it and it doesn't say anything of the sort.

|He's showing re-reflections from
|a Z0-matched source? I don't think I understand all I know about that.
|:-)
|
|73, AC6XG

Jim Kelley wrote:
Interesting reference. Wish I had it. He's showing re-reflections from
a Z0-matched source? I don't think I understand all I know about that.

Nope, the reference is a DC transient buildup to steady-state but the
same principles apply to RMS values.
--
73, Cecil http://www.qsl.net/w5dxp



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Wes Stewart wrote:

Jim Kelley wrote:

|Cecil Moore wrote:
| Shirley, you jest. Reference pages 17-20 in _T-Lines & Networks_ by Johnson.

Now change the context from a DC example to an RF example:

| Consider a T-line with an SWR of 5.8284:1 and a constant 100W Z0-matched
| source. The forward power will be 100W, 150W, 175W, 187.5W, 193.75W,
| 196.875W, 198.4375W, ..., 200W. After steady-state is reached, the
| reflected power is a constant 100W (sans modulation and noise).
|
|Interesting reference. Wish I had it.

I have it and it doesn't say anything of the sort.

I didn't quote anything it says, Wes, I just gave it as a reference. Then I
suggested a different example to be considered. When the SWR is 5.8284:1,
the reflected power is 1/2 of the forward power making mental calculations
easy. The RF example was out of my head, not out of the reference.
--
73, Cecil http://www.qsl.net/w5dxp



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On Tue, 18 Nov 2003 23:32:11 -0600, Cecil Moore
wrote:

|Wes Stewart wrote:
|
| Jim Kelley wrote:
|
| |Cecil Moore wrote:
| | Shirley, you jest. Reference pages 17-20 in _T-Lines & Networks_ by Johnson.
|
|Now change the context from a DC example to an RF example:
|
| | Consider a T-line with an SWR of 5.8284:1 and a constant 100W Z0-matched
| | source. The forward power will be 100W, 150W, 175W, 187.5W, 193.75W,
| | 196.875W, 198.4375W, ..., 200W. After steady-state is reached, the
| | reflected power is a constant 100W (sans modulation and noise).
| |
| |Interesting reference. Wish I had it.
|
| I have it and it doesn't say anything of the sort.
|
|I didn't quote anything it says, Wes, I just gave it as a reference. Then I
|suggested a different example to be considered. When the SWR is 5.8284:1,
|the reflected power is 1/2 of the forward power making mental calculations
|easy. The RF example was out of my head, not out of the reference.

Well then, I'm citing Einstein's Theory of Relatively, but I'm going
to use another example.

How about a DC voltage source and a switch connected to a Zo
transmission line terminated in R = 3*Zo. Sound familiar? (For those
without the text, it's Johnson's example)

Johnson says in part, "The first reflected wave will in turn be
reflected when it reaches the sending end. The terminating impedance
is *zero* (emphasis added) at the end....."

It's quite a leap from a DC situation with zero source impedance to a
RF situation with a matched source.

"Cecil Moore" wrote in message
...
I didn't quote anything it says, Wes, I just gave it as a reference. Then
I
suggested a different example to be considered. When the SWR is 5.8284:1,
the reflected power is 1/2 of the forward power making mental calculations
easy. The RF example was out of my head, not out of the reference.

But how does that relate to the topic of multiple reflections? Perhaps if
you had just quoted the reference instead....?

73, Jim AC6XG