On 20 Jun 2005 09:24:22 -0700, wrote:

Even if Zo=50+j2,
If? Still some doubt after a plunge of 12 orders of magnitude:
If Zo=50+j0.000000000001
Lower precision If's still yield the same logical contradiction to:
then it's close enough!

then the VSWR will still be very close to a 1:1 match.
The significant "if" is in your capacity to demonstrate
Even if Zo=50+j2,

You antenna boys don't build too many
power amplifiers, obviously.

Well, looking at the group title, it does not reveal rec.*.amplifiers,
does it? And you have no credentials to speak of, unless selling to
naifs, like selling dope to school children, falls into the same proof
of authority.

73's
Richard Clark, KB7QHC

On 20 Jun 2005 09:24:22 -0700, wrote:

|
|
|Richard Clark wrote:
| On 20 Jun 2005 01:00:51 -0700, wrote:
| If Zo=50+j0.000000000001,
| And it is not
| then it's close enough!
| hence it follows from this logic, it is not close enough.
|
|
| Even if Zo=50+j2, then the VSWR will
|still be very close to a 1:1 match.
|
| You antenna boys don't build too many
|power amplifiers, obviously.

And you know this how? And it matters why?

But in case it does, I've been building amps since I was a teenager.
Through the years, I built a number of hf and vhf amps for friends.

Here's one I built for myself.

http://www.qsl.net/n7ws/K7CVT_Amp.html

Its replacement with an 8877 is sitting beside me.

Richard Clark wrote:
On 20 Jun 2005 09:24:22 -0700, wrote:

Even if Zo=50+j2,
If? Still some doubt after a plunge of 12 orders of magnitude:
If Zo=50+j0.000000000001
Lower precision If's still yield the same logical contradiction to:
then it's close enough!

then the VSWR will still be very close to a 1:1 match.
The significant "if" is in your capacity to demonstrate
Even if Zo=50+j2,

You antenna boys don't build too many
power amplifiers, obviously.

Well, looking at the group title, it does not reveal rec.*.amplifiers,
does it? And you have no credentials to speak of, unless selling to
naifs, like selling dope to school children, falls into the same proof
of authority.


Oh wait a minute, you're one
of the ham radio guys, right?

That certainly explains a lot!


S.

On 20 Jun 2005 23:16:05 -0700, wrote:

Oh wait a minute, you're one
of the ham radio guys, right?

Flash of insight, that.

That certainly explains a lot!

Must've been a brutal education. Think of the learning grade to climb
Ohm's law.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On 20 Jun 2005 23:16:05 -0700, wrote:

Oh wait a minute, you're one
of the ham radio guys, right?

Flash of insight, that.


Yeah...I guess those funny
little numbers and letters you have
by your name might have something to
do with it...hmmmmm....



That certainly explains a lot!

Must've been a brutal education. Think of the learning grade to climb
Ohm's law.

73's
Richard Clark, KB7QHC


Speaking of "grade", you write
like you're in the 2nd or 3rd.


S.

Ian White, GM3SEK wrote:
"It had been correct, when they incorrectly revised it (the conjugate
reference), now it has been corrected again."

Hope they got it right this time.

My dictionary says: "conjugate - Either of a pair of complex numbers
that are mutually related in that their real parts are identical and the
imaginary part of one is the negative of the imaginary part of the
other.

We find maximum power transfer requires equal resistances in source and
load. Also reactance, if any, be tuned out of the circuit. This is a
conjugate match, such that source and load are conjugates by the
dictionary definition.

Many texts go into detail. I like the story of conjugates given in
"Transmission Lines, Antennas, and Wave Guides", If it were at hand, I
would quote from it. Found it. See page 43. The authors are King, Mimno,
and Wing.

Best regards, Richard Harrison, KB5WZI

"Wes Stewart" *n7ws*@ yahoo.com wrote in message
...
On 20 Jun 2005 09:24:22 -0700, wrote:

|
|
|Richard Clark wrote:
| On 20 Jun 2005 01:00:51 -0700, wrote:
| If Zo=50+j0.000000000001,
| And it is not
| then it's close enough!
| hence it follows from this logic, it is not close enough.
|
|
| Even if Zo=50+j2, then the VSWR will
|still be very close to a 1:1 match.
|
| You antenna boys don't build too many
|power amplifiers, obviously.

And you know this how? And it matters why?

But in case it does, I've been building amps since I was a teenager.
Through the years, I built a number of hf and vhf amps for friends.

Here's one I built for myself.

http://www.qsl.net/n7ws/K7CVT_Amp.html

Its replacement with an 8877 is sitting beside me.

That's a beautiful amp, Wes. I'm curious--how did it handle Slick's
1.040807999:1 swr, from his 50+j2 load impedance?

Walt, W2DU

Walter Maxwell wrote:
"Wes Stewart" *n7ws*@ yahoo.com wrote in message
...
On 20 Jun 2005 09:24:22 -0700, wrote:

|
|
|Richard Clark wrote:
| On 20 Jun 2005 01:00:51 -0700, wrote:
| If Zo=50+j0.000000000001,
| And it is not
| then it's close enough!
| hence it follows from this logic, it is not close enough.
|
|
| Even if Zo=50+j2, then the VSWR will
|still be very close to a 1:1 match.
|
| You antenna boys don't build too many
|power amplifiers, obviously.

And you know this how? And it matters why?

But in case it does, I've been building amps since I was a teenager.
Through the years, I built a number of hf and vhf amps for friends.

Here's one I built for myself.

http://www.qsl.net/n7ws/K7CVT_Amp.html

Its replacement with an 8877 is sitting beside me.

That's a beautiful amp, Wes. I'm curious--how did it handle Slick's
1.040807999:1 swr, from his 50+j2 load impedance?


Looks aren't everything.

It couldn't handle even a 1.04:1 and
just blew out!

Now it's being used as a doorstop...


S.

On 21 Jun 2005 16:46:07 -0700, wrote:



Walter Maxwell wrote:
"Wes Stewart" *n7ws*@ yahoo.com wrote in message
...
On 20 Jun 2005 09:24:22 -0700, wrote:

|
|
|Richard Clark wrote:
| On 20 Jun 2005 01:00:51 -0700, wrote:
| If Zo=50+j0.000000000001,
| And it is not
| then it's close enough!
| hence it follows from this logic, it is not close enough.
|
|
| Even if Zo=50+j2, then the VSWR will
|still be very close to a 1:1 match.
|
| You antenna boys don't build too many
|power amplifiers, obviously.

And you know this how? And it matters why?

But in case it does, I've been building amps since I was a teenager.
Through the years, I built a number of hf and vhf amps for friends.

Here's one I built for myself.

http://www.qsl.net/n7ws/K7CVT_Amp.html

Its replacement with an 8877 is sitting beside me.

That's a beautiful amp, Wes. I'm curious--how did it handle Slick's
1.040807999:1 swr, from his 50+j2 load impedance?


Looks aren't everything.

It couldn't handle even a 1.04:1 and
just blew out!

Now it's being used as a doorstop...


It operated a lot better than "Dr." (not so) Slick does.

He makes a comment that no one here builds amps. I present evidence
to the contrary and this is the best he can do.

What a loser.

I worked about 30 states on two-meters from the depths of AZ using
that amp. The present amp has participated in working all continents
(WAC) on two-meters.

Wes Stewart wrote:

It operated a lot better than "Dr." (not so) Slick does.

He makes a comment that no one here builds amps. I present evidence
to the contrary and this is the best he can do.

What a loser.

I worked about 30 states on two-meters from the depths of AZ using
that amp. The present amp has participated in working all continents
(WAC) on two-meters.

I think Garvin Yee ("Dr. Slick") has WALG (Worked All Los Gatos) and
maybe even WAB (Worked All Berkeley). Does that count?

Roy Lewallen, W7EL

Roy Lewallen wrote:
Wes Stewart wrote:

It operated a lot better than "Dr." (not so) Slick does.

He makes a comment that no one here builds amps. I present evidence
to the contrary and this is the best he can do.


A bunch of pictures of dubious origin...
Would you care to give us some of your design
notes? Or did you build this one from someone
elses schematic?



I think Garvin Yee ("Dr. Slick") has WALG (Worked All Los Gatos) and
maybe even WAB (Worked All Berkeley). Does that count?

Roy Lewallen, W7EL


It certainly does count.

I have also WYM (Worked Yo' Momma!)


Slick

On 21 Jun 2005 23:03:46 -0700, wrote:



Roy Lewallen wrote:
Wes Stewart wrote:

It operated a lot better than "Dr." (not so) Slick does.

He makes a comment that no one here builds amps. I present evidence
to the contrary and this is the best he can do.


What a loser!

A bunch of pictures of dubious origin...

Yes, I'm accustomed to keeping photos around for 30 years of someone
else's work so I can someday pass it off as mine.

Would you care to give us some of your design
notes?

Yes, if I can find them; right after you post some notes and photos of
one of the many amps I'm sure you've built.

Or did you build this one from someone
elses (sic) schematic?

Read the text, Bozo. And then repeat after me: Rho can be greater
than one, rho can be greater than one, rho can be greater than one....

wrote in message
oups.com...


Roy Lewallen wrote:
Wes Stewart wrote:

It operated a lot better than "Dr." (not so) Slick does.

He makes a comment that no one here builds amps. I present evidence
to the contrary and this is the best he can do.


A bunch of pictures of dubious origin...
Would you care to give us some of your design
notes? Or did you build this one from someone
elses schematic?



I think Garvin Yee ("Dr. Slick") has WALG (Worked All Los Gatos) and
maybe even WAB (Worked All Berkeley). Does that count?

Roy Lewallen, W7EL


It certainly does count.

I have also WYM (Worked Yo' Momma!)


Slick

Garvin

There is a flaw in your reasoning. In order for somebody to copy an amp, or
whatever, somebody else still had to design and write up the original. In
many cases, you are here talking to that "somebody else".

Tam/WB2TT

Wes Stewart wrote:
On 21 Jun 2005 23:03:46 -0700, wrote:



Roy Lewallen wrote:
Wes Stewart wrote:

It operated a lot better than "Dr." (not so) Slick does.

He makes a comment that no one here builds amps. I present evidence
to the contrary and this is the best he can do.


What a loser!

A bunch of pictures of dubious origin...

Yes, I'm accustomed to keeping photos around for 30 years of someone
else's work so I can someday pass it off as mine.

Would you care to give us some of your design
notes?

Yes, if I can find them; right after you post some notes and photos of
one of the many amps I'm sure you've built.


Sound to me like you built this one from someone elses
schematic.



Or did you build this one from someone
elses (sic) schematic?

Read the text, Bozo. And then repeat after me: Rho can be greater
than one, rho can be greater than one, rho can be greater than one....


Repeat after me, Dweeb-head: Only with Return Gain, Only with
Return Gain, Only with Return Gain.....



Slick

wrote:
Wes Stewart wrote:
Read the text, Bozo. And then repeat after me: Rho can be greater
than one, rho can be greater than one, rho can be greater than one....

Repeat after me, Dweeb-head: Only with Return Gain, Only with
Return Gain, Only with Return Gain.....

Now, now, boys, be nice. Both of you can be right if you are not
talking about *power* gain. Since you are discussing VSWR, rho can be
greater than one AND the voltage return gain can be greater than one.
The voltage across a resonant circuit depends upon the 'Q' and can
certainly be higher than the applied incident voltage. For that exact
same reason, Vref can be higher than Vfor. It occurs when the load is
the conjugate of Z0 and Z0 is not purely resistive.
--
73, Cecil http://www.qsl.net/w5dxp

wrote:
wrote:

Wes Stewart wrote:

Read the text, Bozo. And then repeat after me: Rho can be greater
than one, rho can be greater than one, rho can be greater than one....

Repeat after me, Dweeb-head: Only with Return Gain, Only with
Return Gain, Only with Return Gain.....


Now, now, boys, be nice. Both of you can be right if you are not
talking about *power* gain. Since you are discussing VSWR, rho can be
greater than one AND the voltage return gain can be greater than one.
The voltage across a resonant circuit depends upon the 'Q' and can
certainly be higher than the applied incident voltage. For that exact
same reason, Vref can be higher than Vfor. It occurs when the load is
the conjugate of Z0 and Z0 is not purely resistive.
--
73, Cecil http://www.qsl.net/w5dxp


Given a 396 meter length of Radio Shack RG58. At 250 kiloherz TLD says
(after some manipulation) that it has a propagation constant of
689.6 X 10^-9 + j7.933 X 10^-3. Zo is 50 -j4.344. Feed it with a
voltage source of 100 volts with a source resistance of 50 ohms.
Put a load on it of j50 ohms. The voltage reflection coefficient at the
load is -4.116 X 10^-3 + j1.091. The absolute value of this number is
1.091, a number greater than one. The power into this line is .1088
Watts. Fine. However, if I calculate the power at the middle of
the line, I get -34.42 watts, a negative number. Moreover, the SWR
calculated at the beginning of the line is -23.21.
What is negative average power?
What does a negative SWR signify?
73,
Tom Donaly, KA6RUH

Tom Donaly wrote:

Given a 396 meter length of Radio Shack RG58. At 250 kiloherz TLD says
(after some manipulation) that it has a propagation constant of
689.6 X 10^-9 + j7.933 X 10^-3. Zo is 50 -j4.344. Feed it with a

Doesn't that imply that the the matched line loss at 0.25MHz is
689.6E-9*20*e^1*100 dB/100m?

That is 0.0006dB/100m, it seems too good to be true!

Owen

Owen wrote:
Tom Donaly wrote:

Given a 396 meter length of Radio Shack RG58. At 250 kiloherz TLD says
(after some manipulation) that it has a propagation constant of
689.6 X 10^-9 + j7.933 X 10^-3. Zo is 50 -j4.344. Feed it with a


Doesn't that imply that the the matched line loss at 0.25MHz is
689.6E-9*20*e^1*100 dB/100m?

That is 0.0006dB/100m, it seems too good to be true!

Owen
Hi Owen,
It is too good to be true. (Just consider it came from an unusually
good batch.) The whole exercise is nonsensical, though,
because it results in negative power and a negative SWR. Increase the
loss to a more realistic value and the negative power goes away as
does the negative SWR while the absolute value of the reflection
coefficient is still greater than 1. I was hoping I could get some
kind of nut philosophical justification for negative average power
out of Cecil, but you sprang the trap.
73,
Tom Donaly, KA6RUH

Tom Donaly wrote:
I was hoping I could get some
kind of nut philosophical justification for negative average power
out of Cecil, but you sprang the trap.

The sign of power can indicate direction as in:

Pnet = Pfor - Pref

or destructive interference as in:

Pnet = P1 + P2 - 2*SQRT(P1*P2)
--
73, Cecil http://www.qsl.net/w5dxp

CAM wrote:
Tom Donaly wrote:

I was hoping I could get some
kind of nut philosophical justification for negative average power
out of Cecil, but you sprang the trap.


The sign of power can indicate direction as in:

Pnet = Pfor - Pref

or destructive interference as in:

Pnet = P1 + P2 - 2*SQRT(P1*P2)
--
73, Cecil http://www.qsl.net/w5dxp


I should have known I could depend on you, Cecil.
73
Tom Donaly, KA6RUH

Tom Donaly wrote:
I should have known I could depend on you, Cecil.

Negative power is a fallout of the math model being used.
For instance, V*I*cos(theta) is negative when theta=180 degrees.
theta=180 degrees for reflected power.

If you have a windmill generator connected to your house
power wiring, you can cause your watthour meter to run
backwards. By convention, that would be negative energy
consumption.
--
73, Cecil http://www.qsl.net/w5dxp

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On Thu, 23 Jun 2005 15:08:09 GMT, "Tom Donaly"
wrote:

The whole exercise is nonsensical

Hi Tom,

You are FOURTH in a growing list of correspondents in the past couple
of weeks who've intentionally posted bum science to prove a point.

Unfortunatle none of those correspondents have made any pointed
impression on the bums they wanted to prove science to.

73's
Richard Clark, KB7QHC

Tom Donaly wrote:
Owen wrote:

Tom Donaly wrote:

Given a 396 meter length of Radio Shack RG58. At 250 kiloherz TLD says
(after some manipulation) that it has a propagation constant of
689.6 X 10^-9 + j7.933 X 10^-3. Zo is 50 -j4.344. Feed it with a



Doesn't that imply that the the matched line loss at 0.25MHz is
689.6E-9*20*e^1*100 dB/100m?

That is 0.0006dB/100m, it seems too good to be true!

Owen

Hi Owen,
It is too good to be true. (Just consider it came from an unusually
good batch.) The whole exercise is nonsensical, though,
because it results in negative power and a negative SWR. Increase the
loss to a more realistic value and the negative power goes away as
does the negative SWR while the absolute value of the reflection
coefficient is still greater than 1. I was hoping I could get some
kind of nut philosophical justification for negative average power
out of Cecil, but you sprang the trap.
73,
Tom Donaly, KA6RUH

Well, you are right I was fooled by your statement "Given a 396 meter
length of Radio Shack RG58" which seemed to say a real cable.

I suspect the source of "negative power" values stems from the
assumption that Power=Real(Vf*If*-Vf*Ir*), whereas it is my
understanding that the power flow at a point on the line is Real(V*I*)
or Real((Vf+Vr)*(If-Ir)* which expands to Real(Vf*If* - Vf*Ir* + Vr*If*
- VrIr*) so that when Power=Real(Vf*If*-Vf*Ir*) is assumed, two of the
terms (- Vf*Ir* + Vr*If*) are being ignored.

The real part of (-Vf*Ir* + Vr*If*) is zero when Zo is real, so they can
be ignored for calculating real power when Zo is real.

In the case of your example, but using real RG58C/U (and Zo is not
real), it looks to me like Real(Vf*If*-Vf*Ir*) is negative out to about
60m from the load, but Real(V*I*) is always positive and always grows
toward the generator.

A graphic showing the behaviour of the terms is at
http://www.vk1od.net/RG58sol.gif .

Owen

PS: My notation: the * postfix unary operator means complex conjugate,
ie (If-Ir)* means compex congugate of (If-Ir).

If you are having trouble viewing the gif file because it has been
zoomed to fit in the browser window, most modern browsers allow you to
zoom it up to 100% size.

In Windows Exploder, hold your cursor over the image until a little
"Expand" control appears, click the "Expand" control and there you go.

In Firefox, just click on the image.

Owen wrote:

I suspect the source of "negative power" values stems from the
assumption that Power=Real(Vf*If*-Vf*Ir*), whereas it is my
understanding that the power flow at a point on the line is Real(V*I*)
or Real((Vf+Vr)*(If-Ir)* which expands to Real(Vf*If* - Vf*Ir* + Vr*If*
- VrIr*) so that when Power=Real(Vf*If*-Vf*Ir*) is assumed, two of the
terms (- Vf*Ir* + Vr*If*) are being ignored.

The real part of (-Vf*Ir* + Vr*If*) is zero when Zo is real, so they can
be ignored for calculating real power when Zo is real.

In the case of your example, but using real RG58C/U (and Zo is not
real), it looks to me like Real(Vf*If*-Vf*Ir*) is negative out to about
60m from the load, but Real(V*I*) is always positive and always grows
toward the generator.

A graphic showing the behaviour of the terms is at
http://www.vk1od.net/RG58sol.gif .


I meant to also mention the response of a typical reflectometer.

The type of reflectometer that samples the voltage at a point, and the
current at the same point to create a voltage proportional to that
current, (such that the magnitude and phase of the voltage due to the
current sample is equal to and opposite to the voltage sample when the
line is terminated in its characteristic impedance,) then adds the two
voltages algebraicly and measures the magnitude of the resultant
responds to Vr, or if it is turned around, to Vf. Such an instrument
does not respond to the two cross product terms terms discussed in the
quote.

So even if you adjusted such a reflectometer so that it nulled on the
true Zo of the cable by adjusting the phase and amplitude of the voltage
same wrt current sample, it would respond to Vf and Vr and could not be
scaled to read forward and reverse power (since it doesn't respond to
the cross product terms).

So, in Tom's case (though with real RG58), a reflectometer of that type,
properly nulled and scaled in Watts would indicate more reflected power
than forward close to the load. The instrument is correctly responding
to the magnitude of the reflection coefficient, but scaling in Watts can
only be valid for Zo real.

Owen


PS: My notation: the * postfix unary operator means complex conjugate,
ie (If-Ir)* means compex congugate of (If-Ir).

If you are having trouble viewing the gif file because it has been
zoomed to fit in the browser window, most modern browsers allow you to
zoom it up to 100% size.

In Windows Exploder, hold your cursor over the image until a little
"Expand" control appears, click the "Expand" control and there you go.

In Firefox, just click on the image.

Richard Clark wrote:
On Thu, 23 Jun 2005 15:08:09 GMT, "Tom Donaly"
wrote:


The whole exercise is nonsensical


Hi Tom,

You are FOURTH in a growing list of correspondents in the past couple
of weeks who've intentionally posted bum science to prove a point.

Unfortunatle none of those correspondents have made any pointed
impression on the bums they wanted to prove science to.

73's
Richard Clark, KB7QHC

Hi Richard,
mea culpa, only what I posted was more parody than
science. At least it was meant to be. Nothing, short of
a visitation by The Creator will make some of the correspondents
to this newsgroup change their thinking about how transmission
lines behave. However, for those who aren't sure of whether
they're right or not, the contemplation of absurdity may
sharpen the understanding. (Or it may not. I'll try not to
post things like this in the future, but can't guarantee
forebearance.)
73,
Tom Donaly, KA6RUH

Tom Donaly wrote:
Nothing, short of
a visitation by The Creator will make some of the correspondents
to this newsgroup change their thinking about how transmission
lines behave.

Hey Tom, what do you think about Ramo & Whinnery's assertion
in _Fields_and_Waves_... 2nd edition, page 291 " .. we are
often most interested in the ratio of power in the reflected
wave to that in the incident wave, and this ratio is given
by the square of the magnitude of [rho], as can be shown by
considering the Poynting vectors: Pz-/Pz+ = |rho|^2 (3)"

Note the plural "Poynting vectors", Pz- for reflected power
and Pz+ for forward power.
--
73, Cecil, http://www.qsl.net/w5dxp


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Nothing, short of
a visitation by The Creator will make some of the correspondents
to this newsgroup change their thinking about how transmission
lines behave.

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

Not even The Creator will get ME to change MY thinking.

Not even if the so-called SWR meter is located in the right place.

Not even if it's a Bird with wings.

Owen wrote:
Tom Donaly wrote:

Owen wrote:

Tom Donaly wrote:

Given a 396 meter length of Radio Shack RG58. At 250 kiloherz TLD says
(after some manipulation) that it has a propagation constant of
689.6 X 10^-9 + j7.933 X 10^-3. Zo is 50 -j4.344. Feed it with a




Doesn't that imply that the the matched line loss at 0.25MHz is
689.6E-9*20*e^1*100 dB/100m?

That is 0.0006dB/100m, it seems too good to be true!

Owen


Hi Owen,
It is too good to be true. (Just consider it came from an unusually
good batch.) The whole exercise is nonsensical, though,
because it results in negative power and a negative SWR. Increase the
loss to a more realistic value and the negative power goes away as
does the negative SWR while the absolute value of the reflection
coefficient is still greater than 1. I was hoping I could get some
kind of nut philosophical justification for negative average power
out of Cecil, but you sprang the trap.
73,
Tom Donaly, KA6RUH


Well, you are right I was fooled by your statement "Given a 396 meter
length of Radio Shack RG58" which seemed to say a real cable.

I suspect the source of "negative power" values stems from the
assumption that Power=Real(Vf*If*-Vf*Ir*), whereas it is my
understanding that the power flow at a point on the line is Real(V*I*)
or Real((Vf+Vr)*(If-Ir)* which expands to Real(Vf*If* - Vf*Ir* + Vr*If*
- VrIr*) so that when Power=Real(Vf*If*-Vf*Ir*) is assumed, two of the
terms (- Vf*Ir* + Vr*If*) are being ignored.

The real part of (-Vf*Ir* + Vr*If*) is zero when Zo is real, so they can
be ignored for calculating real power when Zo is real.

In the case of your example, but using real RG58C/U (and Zo is not
real), it looks to me like Real(Vf*If*-Vf*Ir*) is negative out to about
60m from the load, but Real(V*I*) is always positive and always grows
toward the generator.

A graphic showing the behaviour of the terms is at
http://www.vk1od.net/RG58sol.gif .

Owen

PS: My notation: the * postfix unary operator means complex conjugate,
ie (If-Ir)* means compex congugate of (If-Ir).

If you are having trouble viewing the gif file because it has been
zoomed to fit in the browser window, most modern browsers allow you to
zoom it up to 100% size.

In Windows Exploder, hold your cursor over the image until a little
"Expand" control appears, click the "Expand" control and there you go.

In Firefox, just click on the image.

I used the complicated expressions for V and I found
in _Field and Wave Electromagnetics_ by David K. Cheng on page 468,
and then found the power by taking the real part of VI*. If you're
interested in doing it the hard way, you can first find V and I,
then take (V + ZoI)/2Sqrt(ReZo) and call that a. Then take
(V - Zo*I)/2Sqrt(ReZo) and call that b. The power is then just
|a|^2 - |b|^2. This last comes from _Microwave Engineering Using
Microstrips_ by E.F. Fooks and R.A Zakarevicius.
Before doing any of this, though, be sure the propagation constant
is the right one for the Zo of the line. The books give
the propagation constant for a transmission line as sqrt((R + jwL)(G +
jwC)), and Zo as sqrt((R + jwL)/(G + jwL)) so it's reasonable to assume
the two are related. In other words, it doesn't seem as if you can just
pick numbers out of a hat for the two quantities and expect them to mean
anything.
73,
Tom Donaly, KA6RUH

"Cecil Moore" wrote in message
...
Tom Donaly wrote:
Nothing, short of
a visitation by The Creator will make some of the correspondents
to this newsgroup change their thinking about how transmission
lines behave.

Hey Tom, what do you think about Ramo & Whinnery's assertion
in _Fields_and_Waves_... 2nd edition, page 291 " .. we are
often most interested in the ratio of power in the reflected
wave to that in the incident wave, and this ratio is given
by the square of the magnitude of [rho], as can be shown by
considering the Poynting vectors: Pz-/Pz+ = |rho|^2 (3)"

Note the plural "Poynting vectors", Pz- for reflected power
and Pz+ for forward power.
--
73, Cecil, http://www.qsl.net/w5dxp

Cecil, concerning Poynting vectors, may I refer you to the last paragraph of
Page 8-3 in Reflections 1, or the last paragraph beginning on Page 8-2 of
Reflections 2.

Walt, W2DU

Walter Maxwell wrote:

"Cecil Moore" wrote:
... Ramo & Whinnery's assertion
in _Fields_and_Waves_... 2nd edition, page 291 " .. we are
often most interested in the ratio of power in the reflected
wave to that in the incident wave, and this ratio is given
by the square of the magnitude of [rho], as can be shown by
considering the Poynting vectors: Pz-/Pz+ = |rho|^2 (3)"

Note the plural "Poynting vectors", Pz- for reflected power
and Pz+ for forward power.

Cecil, concerning Poynting vectors, may I refer you to the last paragraph of
Page 8-3 in Reflections 1, or the last paragraph beginning on Page 8-2 of
Reflections 2.

Thanks Walt, it's been about 15 years since I first read
that short and sweet chapter in "Reflections 1".
--
73, Cecil http://www.qsl.net/w5dxp

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