Peter, what an excellent, straight-forward, plain
-English, explanation. And you didn't enlist the
aid of a single guru. Not even Terman or the
ARRL handbook. ;o)
-----
Reg

"Peter O. Brackett" wrote in message link.net...
Slick:

[snip]
And not the complex conjugate of Z0.
:
:
This is ABSOLUTELY WRONG!

The reflection coefficient is zero only when the Zload
is the conjugate of the Zo.

Go look it up in any BASIC RF book!

Slick
[snip]

Easy now boy! You'r almost as bad as me!


ok...taking some deep breaths here...

:)


It is entirely possible, in fact I know this to be true, that there can be
more than one *definition* of "the reflection coefficient". And so... one
cannot say definitively that one particular defintion is WRONG.


But we need a definite definition, otherwise everyone has their
own standard, so when i say "reflection coefficient", you will will
know what i mean, not something else.

When i say "Elephant", hopefully the same animal pops into your
head.



If the definition of the reflection coefficient is given as rho = (Z - R)/(Z
+ R) then that's what it is. This particular definition corresponds to the
situation which results in rho being null when the unknown Z is equal to the
reference impedance R, i.e. an "image match". If the definition is given as
rho = (Z - conj(R))/(Z + conj(R)) then rho will be null when the unknown Z
is equal to the conjugate of the reference impedance conj(R), i.e. a
"conjugate match".



Correction: rho = (Z - conj(R))/(Z + (R)), the conjugate being
only in the denominator.


Slick

Roy Lewallen wrote in message ...
I'm eagerly awaiting your analysis showing how and why it's wrong. Or
simply which of the statements and equations I wrote are incorrect, and
what the correct statement or equation should be and why. Or even a
simple numerical example that illustrates the relationship between
reflection and power transfer.


I think Reg put it best:

"Dear Dr Slick, it's very easy.

Take a real, long telephone line with Zo = 300 - j250 ohms at 1000 Hz.

Load it with a real resistor of 10 ohms in series with a real
inductance of
40 millihenrys.

The inductance has a reactance of 250 ohms at 1000 Hz.

If you agree with the following formula,

Magnitude of Reflection Coefficient of the load, ZL, relative to line
impedance

= ( ZL - Zo ) / ( ZL + Zo ) = 1.865 which exceeds unity,

and has an angle of -59.9 degrees.

The resulting standing waves may also be calculated.

Are you happy now ?"
---
Reg, G4FGQ


If it were not for Reg pointing out this example, i wouldn't have
researched and corrected my original, "purely real" Zo post with the
more general conjugate Zo formula.

And i researched it because i knew that you cannot have a R.C.
greater than one for a passive network (you can only have a R.C.
greater than one for an active network, which would be a "return gain"
instead of a "return loss"), so i knew that when Zo is complex, my
original post must have been wrong.

Roy, you and i have been slinging mud at each other, but i do
respect the things you have taught me, and i do thank you for deriving
the uV/meter equation for dipoles.

But i want you to know that i'm not doing this for my ego. Didn't
i admit that calling antennas "transducers" was a better word than
"transformers", albiet 2 transducers make 1 transformer?

I have yet to see you admit that someone else has a point.

Intelligent people can be close-minded, that is for certainly, in
which case, their intelligence is blunted.



Slick

"David Robbins" wrote in message ...
"Dr. Slick" wrote in message
...
Roy Lewallen wrote in message
...

A. The one just posted by Peter, (Zl - Z0conj) / (Zl + Z0conj)

B. Slick's, (Zl - Z0conj) / (Zl + Z0)

This is the correct formula.

it is??? -10 points and repeat last week's homework.


Who are you to correct my homework? Look it up yourself

It's absolutely the correct formula

For passive circuits, 0=[rho]=1,

And strictly speaking: Reflection Coefficient =
(Zl-Zo*)/(Zl+Zo)

Where * indicates conjugate.



C. The one in all my texts and used by practicing engineers, (Zl - Z0) /
(Zl + Z0)



This formula is correct too, but only because most texts assume a
purely real Zo.

F+, and take the whole class again.


Slick

I ain't like most engineers boy, and i'm certainly more edumacated than
you!

You don't know Sh**!


Slick


Hi, Garvin, you old gwee.
Does your family know you're monkeying around like this on
the net?
73,
Tom Donaly, KA6RUH

Roy Lewallen wrote:
I've never seen the (voltage) reflection coefficient defined as anything
other than the ratio of reflected voltage to forward voltage. Do you
have any reputable source that defines it differently?

s11 is a reflection coefficient that has the special condition that
a2 must be equal zero. When a2 is not equal zero, the s11 reflection
coefficient and the apparent reflection coefficient are not the same.
--
73, Cecil http://www.qsl.net/w5dxp



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Thank you. That is, of course, for a two port network. Since we've been
talking strictly about a one-port case (I think, anyway), let me
rephrase the question. Do you have any reputable source that defines the
reflection coefficient for a one-port network as anything other than Vr/Vf.

Although it's not really relevant to the discussion at hand, I believe a
valid argument could be made that if a2 isn't equal to zero, then S11
isn't a reflection coefficient at all. It surely isn't the reflection
coefficient at port 1, anyway. But it's a point I'll happily concede in
lieu of fussing about it.

Roy Lewallen, W7EL

W5DXP wrote:
Roy Lewallen wrote:

I've never seen the (voltage) reflection coefficient defined as
anything other than the ratio of reflected voltage to forward voltage.
Do you have any reputable source that defines it differently?


s11 is a reflection coefficient that has the special condition that
a2 must be equal zero. When a2 is not equal zero, the s11 reflection
coefficient and the apparent reflection coefficient are not the same.

Now that the various typo mistakes have been corrected, and putting
aside for the moment the name calling and ad hominem arguments, could
it be that _both_ sides in this discussion are correct? Camp 'A' says
that the reflection coefficient is computed the classical way, without
using Zo conjugate, and offers various mathematical proofs and
discussions of infinitely long lines. Camp 'B' says the reflection
coefficient is computed with Zo* (Zo conjugate) in the numerator, and
offers explanations dealing with the conservation of energy and
maximum transfer of power.

Both sides may be correct since they are talking about _two different_
meanings for the term "reflection coefficient." One has to do with
voltage (or current) traveling waves and the other has to do with
power. Quoting two references:

###

From Chipman, "Theory and Problems of Transmission Lines," 1968:

Section 7.1, Reflection coefficient for voltage waves:
[Discussion and math, then] ...
rho = (ZL - Zo) / (ZL + Zo)

Section 7.6, Complex characteristic impedance
[Various mathematical manipulations, then] ... "the maximum possible
value for |rho| is found to be 1 + sqrt(2) or about 2.41. ... [T]he
principal of conservation of energy is not violated even when the
magnitude of the [voltage wave] reflection coefficient exceeds unity."

[then more math, then] ... "The conclusion is somewhat surprising,
though inescapable, that a transmission line can be terminated with a
[voltage wave] reflection coefficient whose magnitude is as great as
2.41 without there being any implication that the power level of the
reflected wave is greater than that of the incident wave."

[then a discussion of a source with internal impedance Zo connected to
a line with characteristic impedance also Zo that is terminated with a
load of impedance ZL, then] "... more power will be delivered to a
terminal load impedance Zo* [conjugate of Zo] that produces a
reflected [voltage] wave on the line than to a terminal load impedance
Zo that produces no reflected [voltage] wave."

So Chipman states quite clearly that zero reflected voltage wave
magnitude does _not_ mean maximum power transfer. On the contrary,
maximum power is transferred only when there is a non-zero voltage
wave reflection (assuming a complex Zo line). Counter arguments along
the lines of "Well that doesn't seem right to me so therefore Chipman
must be wrong" don't carry much weight given Chipman's credentials.

###

From Kurokawa, "Power Waves and the Scattering Matrix," IEEE
Transactions on Microwave Theory and Techniques, March 1965:

Section 2, explanation of and mathematical definition of the concept
of "power waves," explicitly noted by the author to be distinct from
the more commonly discussed voltage and current traveling waves.

Section 3, definition of the reflection coefficient [for power waves]:
s = (ZL - Zo*) / (ZL + Zo)
with a footnote "[Only w]hen Zo is real and positive this is the
voltage wave reflection coefficient." Kurokawa takes pains to make it
clear that his "s" power wave reflection coefficient is not the same
as the (usually rho or Gamma) voltage wave reflection coefficient.

Section 9, comparison with [voltage and current] traveling waves:
"... since the [voltage or current] traveling wave reflection
coefficient is given by (ZL - Zo) / (ZL + Zo) [note no conjugate] and
the maximum power transfer takes place when ZL=Zo*, ... it is only
when there is a certain reflection in terms of [voltage or current]
traveling waves that the maximum power is transferred from the line to
the load."

So Kurokawa agrees with Chipman concerning the condition for maximum
power transfer. Kurokawa also defines two different reflection
coefficients, both in the same paper.

[In some of the above quotes I have altered the subscript letter
assigned to Z, merely for consistency between the two references.]

###

So, it seems to me, everybody can agree as long as it is understood
that there are different meanings for the term "reflection
coefficient." One meaning, and its mathematical definition, applies
to voltage or current waves. The other, with a slightly different
mathematical definition, applies to the power transfer from a line to
a load. They are one and the same only when the reactive portion of
Zo (Xo) is ignored. It may or may not be acceptable to do so,
depending on the attenuation of the line and the frequency. Lossy
lines and lower frequencies yield more negative values for the Xo
component of Zo.

You can use Reg's COAXPAIR or my TLDetails program to do the math and
show concrete examples. Try something like 100 feet of RG-174 at 0.1
MHz, terminated with loads equivalent to Zo and then Zo conjugate, and
compare the rho (or SWR) figures versus the power delivered to the
load for each case. When the termination equals Zo conjugate, note
that the total dB loss is actually _less_ than the matched line loss.
As counter intuitive as this may sound, Chipman offers an explanation
on page 139. (And as others are sure to point out, this makes
absolutely no difference in practical applications and is of academic
interest only.)

Copy of the Kurokawa paper, in pdf format, available on request via
private email. I've obtained copies of Chipman, on two separate
occasions, from Powell's in Portland.

Dan, AC6LA
www.qsl.net/ac6la/

"Dr. Slick" wrote in message
om...
"David Robbins" wrote in message
...
"Dr. Slick" wrote in message
...
Roy Lewallen wrote in message
...

A. The one just posted by Peter, (Zl - Z0conj) / (Zl + Z0conj)

B. Slick's, (Zl - Z0conj) / (Zl + Z0)

This is the correct formula.

it is??? -10 points and repeat last week's homework.


Who are you to correct my homework? Look it up yourself



i did, and its wrong.... but you cut off my reference in your reply. there
is no conjugate term in the complete solution for a real line.

Dan wrote:

So Chipman states quite clearly that zero reflected voltage wave
magnitude does _not_ mean maximum power transfer. On the contrary,
maximum power is transferred only when there is a non-zero voltage wave
reflection (assuming a complex Zo line). Counter arguments along the
lines of "Well that doesn't seem right to me so therefore Chipman must
be wrong" don't carry much weight given Chipman's credentials.

Thanks for that posting, Dan, and for what looks like a very clear
summary.

Just one point, about that very last word: what are Chipman's
"credentials", really? They are not that he is a well-known[*] textbook
author, college professor, PhD, or anything like that. This discussion
is already way overloaded with personal "credentials" of that kind!

Chipman's true credentials are that he has thought about this subject,
noticed the apparent problem, worked it out, and presented clear,
correct conclusions in a way that other people can follow. Those are the
only credentials that really count.


[*] Well-known to some college students in the USA, perhaps? I'd never
heard of him, but Dan's summary suggests this book might be worth
looking for.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

Roy Lewallen wrote:
Although it's not really relevant to the discussion at hand, I believe a
valid argument could be made that if a2 isn't equal to zero, then S11
isn't a reflection coefficient at all. It surely isn't the reflection
coefficient at port 1, anyway.

Actually, it is, Roy. s11 is the *physical* reflection coefficient.
For instance, in the following two-port network:

source---50 ohm feedline---+---1/2WL 150 ohm feedline---50 ohm load

s11 is *defined* as the input reflection coefficient with the output
port terminated by a matched load (ZL=150 ohms sets a2=0). s11
continues to be *defined* as 0.5 even when a2 is not zero.

s11 = (150-50)/(150+50) = 0.5

Since a Z0-match exists at '+', the reflection coefficient on the
50 ohm feedline is zero. rho = Sqrt(Pref/Pfwd)

For a two-port network with a2 not equal to zero, the reflection
coefficient 's11' is NOT equal to the reflection coefficient 'rho'.

The energy analysis on my web page deals only with physical reflection
coefficients. If 'rho' is not a physical reflection coefficient, then
it is the END RESULT of a mathematical calculation and is not the
CAUSE of anything. If a source doesn't "see" a physical impedance
discontinuity, it doesn't "see" anything except forward and reflected
waves. Coherent waves traveling in opposite directions are "unaware" of
each other. Coherent waves traveling in the same direction merge, lose
their separate identies, and become indistinguishable from one another.
--
73, Cecil http://www.qsl.net/w5dxp



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Dan wrote:
Now that the various typo mistakes have been corrected, and putting
aside for the moment the name calling and ad hominem arguments, could
it be that _both_ sides in this discussion are correct? Camp 'A' says
that the reflection coefficient is computed the classical way, without
using Zo conjugate, and offers various mathematical proofs and
discussions of infinitely long lines. Camp 'B' says the reflection
coefficient is computed with Zo* (Zo conjugate) in the numerator, and
offers explanations dealing with the conservation of energy and
maximum transfer of power.

Both sides may be correct since they are talking about _two different_
meanings for the term "reflection coefficient." One has to do with
voltage (or current) traveling waves and the other has to do with
power.

If a lossy line is terminated with the complex Z0,
there is no reflection from the load, but the
maximum possible power is not delivered. If the
*load* is made equal to the complex conjugate of
Z0 the maximum *forward power* is delivered but
there is a reflected power (VSWR is not 1:1).

It is difficult to say that the maximum *power* is
delivered without knowing the generator impedance,
since it is involved in any so-called "conjugate
match". For a lossy line, the idea of conjugate
match is, at best, very approximate anyway. And
generator impedance is a mystery in most, but not
all, transmitter PA situations. One possible
exception: a large amount of negative feedback
helps to determine, to some extent, output
impedance, for a signal with time-varying
amplitude (e.g. SSB).

It seems to me to be clear that the use of Z0* in
the reflection coefficient equation has not been
corroborated (see Roy's post), but the use of
ZL=ZO* has been. The two ideas are not equivalent.

After looking at some examples, using the exact
complex hyperbolic equations with Mathcad, it is
obvious that a line must be very lossy to make a
significant difference whether ZL or ZL* is used
to terminate the line. Still, it is important to
understand the basic principles involved, so this
exercise is not foolishness at all.

A word about "credentials". We all respect
established and competent authors. But I have
noticed on several occasions that blind faith has
some exceptions. As an experienced author, I am
personally familiar with this problem.

G. Gonzalez (highly respected) "Microwave
Transistor Amplifiers" second edition, has a good
discussion of Power Waves, based on Kurokawa (I
also have his article). There are no transmission
lines, and the term ZS* (ZS=generator impedance)
is used. In particular, a power wave reflection
coefficient is defined:

Gp = (ZL-ZS*)/(ZL+ZS)

which looks quite familiar, with ZS replacing Z0.
Also, a voltage reflection coefficient:

Gv = [Zs/Zs*] x [(ZL-ZS*)/(ZL+ZS)]

and a current reflection coefficient

Gv = Gp.

The author also defines two-port scattering
parameters in terms of power waves, in which ZS*
and ZL* appear.

For the purposes of the present topic, involving
transmission lines, it seems best to stay away
from power waves, without a lot more studying.

Bill W0IYH

Cecil:

[snip]
s11 is a reflection coefficient that has the special condition that
a2 must be equal zero. When a2 is not equal zero, the s11 reflection
coefficient and the apparent reflection coefficient are not the same.
--
73, Cecil http://www.qsl.net/w5dxp
[snip]

No! The scattering paramters, e.g for a two-port the s11, s12, s21 and s22
are all parameters fixed by the network and are not dependent upon either
the independent or dependent variables! i.e. b1 = s11*a1 + s12*a2, and b2
= s21*a1 + s22* a2.

--
Peter K1PO
Indialantic By-the-Sea, FL.

Roy:

[snip]
"Roy Lewallen" wrote in message
...
This is interesting. But how did it lead you to the equation you
determined must be correct? That is, what definition of reflection
coefficient did you start with, where did you get it, and how did you
get from there to the reflection coefficient equation you presented?

I assume that, consistent with the admonition in the last paragraph of
your posting, you were "careful to follow through and be consistent with
your definitions, measurements, algebra, and arithmetic". It would be
very instructive for us to be able to follow the process you did in
coming to what you feel is the "right answer".

Roy Lewallen, W7EL
[snip]

I followed up with a complete, and I hope simple and easy to follow,
algebraic development in another nearby posting. Have a look and let us
know what you think.

BTW... I don't necessarily agree with Slick's defintition of the reflection
coefficient and for sure, his is not the one I use. But I will defend to
the death his right to use the one he defines, as long as all of his
subsequent calculations and measurements are consistent with that
definition.

Slice and I will always end up with the same voltages v and currents i, it's
just that our wave variables a and b won't agree!

Viewing "waves" is just a viewpoint! One has to view them "through" an
instrument called a reflectometer. When viewed through ammeters and
voltmeters we will all measure the same things.

Only the "electricals" the v and I are "real"! The "waves" the a and b are
just different manifestations of v and i as viewed through and instrument
[reflectometer] using a, perhaps arbitrary, reference impedance, or matrix
transformation.

Sorry Cecil. :-)

--
Peter K1PO
Indialantic By-the-Sea, FL.

Reg:

[snip]
"Reg Edwards" wrote in message
...
Peter, what an excellent, straight-forward, plain
-English, explanation. And you didn't enlist the
aid of a single guru. Not even Terman or the
ARRL handbook. ;o)
-----
Reg
[snip]

Heh, heh...

I beleive in working it all out from first principles, can't trust anybody
else, except of course you and your wonderful programs. :-)

--
Peter K1PO
Indialantic By-the-Sea, FL.

William E. Sabin wrote:
Dan wrote:

Now that the various typo mistakes have been corrected, and putting
aside for the moment the name calling and ad hominem arguments, could
it be that _both_ sides in this discussion are correct? Camp 'A' says
that the reflection coefficient is computed the classical way, without
using Zo conjugate, and offers various mathematical proofs and
discussions of infinitely long lines. Camp 'B' says the reflection
coefficient is computed with Zo* (Zo conjugate) in the numerator, and
offers explanations dealing with the conservation of energy and
maximum transfer of power.

Both sides may be correct since they are talking about _two different_
meanings for the term "reflection coefficient." One has to do with
voltage (or current) traveling waves and the other has to do with
power.


If a lossy line is terminated with the complex Z0, there is no
reflection from the load, but the maximum possible power is not
delivered. If the *load* is made equal to the complex conjugate of Z0
the maximum *forward power* is delivered but there is a reflected power
(VSWR is not 1:1).

It is difficult to say that the maximum *power* is delivered without
knowing the generator impedance, since it is involved in any so-called
"conjugate match". For a lossy line, the idea of conjugate match is, at
best, very approximate anyway. And generator impedance is a mystery in
most, but not all, transmitter PA situations. One possible exception: a
large amount of negative feedback helps to determine, to some extent,
output impedance, for a signal with time-varying amplitude (e.g. SSB).

It seems to me to be clear that the use of Z0* in the reflection
coefficient equation has not been corroborated (see Roy's post), but the
use of ZL=ZO* has been. The two ideas are not equivalent.

After looking at some examples, using the exact complex hyperbolic
equations with Mathcad, it is obvious that a line must be very lossy to
make a significant difference whether ZL or ZL*

Correction: Z0 or Z0*

is used to terminate the
line. Still, it is important to understand the basic principles
involved, so this exercise is not foolishness at all.

A word about "credentials". We all respect established and competent
authors. But I have noticed on several occasions that blind faith has
some exceptions. As an experienced author, I am personally familiar with
this problem.

G. Gonzalez (highly respected) "Microwave Transistor Amplifiers" second
edition, has a good discussion of Power Waves, based on Kurokawa (I also
have his article). There are no transmission lines, and the term ZS*
(ZS=generator impedance) is used. In particular, a power wave reflection
coefficient is defined:

Gp = (ZL-ZS*)/(ZL+ZS)

which looks quite familiar, with ZS replacing Z0. Also, a voltage
reflection coefficient:

Gv = [Zs/Zs*] x [(ZL-ZS*)/(ZL+ZS)]

and a current reflection coefficient

Gv = Gp.

Correction: Gi = Gp


The author also defines two-port scattering parameters in terms of power
waves, in which ZS* and ZL* appear.

For the purposes of the present topic, involving transmission lines, it
seems best to stay away from power waves, without a lot more studying.

Bill W0IYH

Slick:

[snip]
Correction: rho = (Z - conj(R))/(Z + (R)), the conjugate being
only in the denominator.

Slick
[snip]

Well here we have to part company.

Not using the same "thing" in both numerator and denominator *is* being
inconsistent!

See my algebraic development in another posting on this thread.

--
Peter K1PO
Indialantic By-the-Sea, FL.

On Sun, 24 Aug 2003 15:27:02 GMT, "Peter O. Brackett"
wrote:

See anything wrong with this analysis?


Hi Peter,

One thing: you are expecting everyone to agree that the source has a
characteristic Z.

The chasm that separates factions is found in this alone where many
who say, no "it is NOT 50 Ohms" (or "it doesn't matter") are loath to
come up with an actual value to conjugate (in other words, a sterile
position). Such a forced choice leads obviously to the deflation of
pet theories. To date their best argument is you cannot possibly know
that value (for any of a variety of reasons, unrelated to simply
sitting down at the bench and measuring an actual value). In short,
institutionalized ignorance, embraced with a mystic missionary zeal,
is their crowing logic.

But I do enjoy their examples and logic puzzles reminiscent of the
necromancer's formulæ for transmutation of gold into lead. The
unrequited dreams would be fulfilled if only the discovery of the
Philosopher's Stone could be realized. Hence debate proceeds with the
leaps and twirls of zen-cartwheeling.

73's
Richard Clark, KB7QHC

Richard Clark wrote:


To date their best argument is you cannot possibly know
that value (for any of a variety of reasons, unrelated to simply
sitting down at the bench and measuring an actual value). In short,
institutionalized ignorance, embraced with a mystic missionary zeal,
is their crowing logic.

The problem lies in the difficulty of measuring or
calculating Zs, especially for signals that have
large variations in amplitude, such as SSB.

There is no institutionalized ignorance, just a
lot of skepticism regarding the reliability of the
analysis methods and the measurement methods.

Bill W0IYH

On Sun, 24 Aug 2003 12:22:34 +0100, "Ian White, G3SEK"
wrote:

[*] Well-known to some college students in the USA, perhaps? I'd never
heard of him, but Dan's summary suggests this book might be worth
looking for.

Hi Ian,

Any university student in course work relating to Transmission lines
would have a copy. It comes from a successful line of tutorials known
as "Schaum's Outlines."

Chipman also discusses the relevancy of the characteristic Z of a
source to SWR, which is tucked away in the unread part. ;-)

73's
Richard Clark, KB7QHC

On Sun, 24 Aug 2003 11:26:00 -0500, "William E. Sabin"
sabinw@mwci-news wrote:

Richard Clark wrote:


To date their best argument is you cannot possibly know
that value (for any of a variety of reasons, unrelated to simply
sitting down at the bench and measuring an actual value). In short,
institutionalized ignorance, embraced with a mystic missionary zeal,
is their crowing logic.

The problem lies in the difficulty of measuring or
calculating Zs, especially for signals that have
large variations in amplitude, such as SSB.

There is no institutionalized ignorance, just a
lot of skepticism regarding the reliability of the
analysis methods and the measurement methods.

Bill W0IYH


Hi Bill,

If the best that skeptics can offer to methods described and data
obtained are "it's not important" or "the time is not justified going
there;" then that is not a particularly high bar of excellence in
reasoning and remains thinly veiled institutionalized ignorance.

Or call it intellectual glaciation, the insurmountable obstacles plea
as argument defending naysaying is frayed and time worn. This is all
"special engineering olympics" caliber justification. Perhaps the
correspondents who enter into these debates should have their
handicaps posted somewhere so the odds makers could weigh the risks of
following such gold medal champions.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...
Chipman also discusses the relevancy of the characteristic Z of a
source to SWR, which is tucked away in the unread part. ;-)

73's
Richard Clark, KB7QHC

Richard,

There used to be a Dr. Chipman who taught a fields/waves course at the
University of Toledo (OH) in the 60s. Do you know if it is the same guy?

Tam/WB2TT

"Dr. Slick" wrote in message
om...
(Tdonaly) wrote in message
...


You know, Garvin, if you can't even tell the numerator from the
denominator, you're in sad shape. Maybe you should stick
to playing your guitar and doodling.
73,
Tom Donaly, KA6RUH


Maybe you should stick to your all-night wanking sessions...


Slick

one word --- blisters

"Dr. Slick" wrote in message
om...

[s]**2 = [(ZL - Zo*) / (ZL + Zo)]**2 the "power reflection
coefficent".

Note the squares.

yes, please do note the squares.... and remember, just because

[s]**2 = [(ZL - Zo*) / (ZL + Zo)]**2
does NOT mean that
s = (ZL - Zo*) / (ZL + Zo)

this is the one big trap that all you guys that like to use power in your
calculations fall into. just because you know the power doesn't mean that
you know squat about the voltage and current on the line. you can not work
backwards. that is why it is always better to work with voltage or current
waves and then in the end after you have solved all those waves you can
always calculate power if you really need to know it.

Peter O. Brackett wrote:
s11 is a reflection coefficient that has the special condition that
a2 must be equal zero. When a2 is not equal zero, the s11 reflection
coefficient and the apparent reflection coefficient (rho) are not the same.

No! The scattering paramters, e.g for a two-port the s11, s12, s21 and s22
are all parameters fixed by the network and are not dependent upon either
the independent or dependent variables! i.e. b1 = s11*a1 + s12*a2, and b2
= s21*a1 + s22* a2.

I'm sorry, Peter, but you probably misunderstood me. s11 cannot possibly
be the same as 'rho' when a2=100 watts.

s11 = b1/a1 when a2=0.

b1 is equal to something else if a2 is not zero.

rho = Sqrt(Pref/Pfwd)

These do NOT have to be the same values. That's all I was saying.
--
73, Cecil http://www.qsl.net/w5dxp



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Peter O. Brackett wrote:
Only the "electricals" the v and I are "real"! The "waves" the a and b are
just different manifestations of v and i as viewed through and instrument
[reflectometer] using a, perhaps arbitrary, reference impedance, or matrix
transformation.

Sorry Cecil. :-)

Sorry Peter, quantum physics disagrees with you. It's the electrons,
photons, and virtual photons that are real. :-)
--
73, Cecil http://www.qsl.net/w5dxp



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Peter O. Brackett wrote:
I beleive in working it all out from first principles, can't trust anybody
else, except of course you and your wonderful programs. :-)

Ever try to develop Morse code from first principles? :-)
--
73, Cecil http://www.qsl.net/w5dxp



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Dr. Slick wrote:
I've got the same paper. It's a bit confusing, because then he
calls [s]**2 = [(ZL - Zo*) / (ZL + Zo)]**2 the "power reflection
coefficent". Where if you take the square root to the power reflection
coefficient, you should get the voltage r. c. So perhaps s =
(ZL - Zo*) / (ZL + Zo) really IS the voltage R. C., even in this paper!

There's no confusion at all (except here on this newsgroup). The power
reflection coefficient is known as the "Reflectance" in optics. The
voltage reflection coefficient that we know and love in RF is one
of the Fresnel (1788-1827) Equations. In optics, it is known as the
"amplitude reflection coefficient", equation 4.34 in _Optics_, 4th edition.

May I suggest that everyone obtain a copy of _Optics_, by Hecht, and
contribute to his/her basic understanding of EM waves. Light was
detectable eons before RF and thus had an extreme head start. We are
presently arguing principles that were already resolved by the end of
the 18th century.
--
73, Cecil http://www.qsl.net/w5dxp



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OHH MY GHOD!! Your sooo smart to find my real name!

(slaps head in stupidity, i forgot about a Google search, Dammit!)

:)


Slick

Ah, the fatuous irony of youth. Say, Yee, I'm curious. Did you ever attend
Lowell? Also, what got you interested in radio? I would think a self-anointed
artist cum musician like you would avoid technical subjects like the
plague. You don't seem to be doing very well at any rate.
73,
Tom Donaly, KA6RUH

Sorry Peter, quantum physics disagrees with you. It's the electrons,
photons, and virtual photons that are real. :-)
--
73, Cecil http://www.qsl.net/w5dxp


What's the radius of a virtual photon, Cecil?
73,
Tom Donaly, KA6RUH

"Peter O. Brackett" wrote in message link.net...
Slick:

[snip]
Correction: rho = (Z - conj(R))/(Z + (R)), the conjugate being
only in the denominator.

Slick
[snip]

Well here we have to part company.

Not using the same "thing" in both numerator and denominator *is* being
inconsistent!

See my algebraic development in another posting on this thread.


Opps Again!

Correction: rho = (Z - conj(R))/(Z + (R)), the conjugate being
only in the numerator.


Slick

Cecil:

[snip]
Ever try to develop Morse code from first principles? :-)
--
73, Cecil http://www.qsl.net/w5dxp
[snip]

Even Morse didn't do that! Apparently historians believe that his faithful
servant Vail did that.

--
Peter K1PO
dah di dah

"David Robbins" wrote in message ...
"Dr. Slick" wrote in message
om...

[s]**2 = [(ZL - Zo*) / (ZL + Zo)]**2 the "power reflection
coefficent".

Note the squares.

yes, please do note the squares.... and remember, just because

[s]**2 = [(ZL - Zo*) / (ZL + Zo)]**2
does NOT mean that
s = (ZL - Zo*) / (ZL + Zo)

this is the one big trap that all you guys that like to use power in your
calculations fall into. just because you know the power doesn't mean that
you know squat about the voltage and current on the line. you can not work
backwards. that is why it is always better to work with voltage or current
waves and then in the end after you have solved all those waves you can
always calculate power if you really need to know it.


yes, but he does say that s = (ZL - Zo*) / (ZL + Zo) , first.

But he foolishly calls it a "power wave R. C."

Then he squares the magnitudes [s]**2 = [(ZL - Zo*) / (ZL +
Zo)]**2

And calls this the "power R. C."


The bottom label is fine, we've all see this before, as the ratio
of the RMS incident and reflected voltages, when squared, should give
you the ratio of the average incident and reflected powers, or the
power R. C.


But to call the voltage reflection coefficient a "power wave R.
C."
is really foolish, IMO.


Slick

Design, development and test of circuit and board level RF designs
including impedance matching networks (simulating on MIMP) for E-PHEMT
power amplifiers for the GSM, DCS, and PCS cellular bands
(880MHz-1900MHz). Simulations on ADS to assess manufacturability and
robustness. Bias tuning for EDGE mode EVM and Adjacent channel power.
Optimize circuit design and board layout for PAE, gain flatness,
stability under mismatched loads, receive-band noise, AM to PM, input
VSWR and harmonic suppression.
Design and construction of FM stereo multiplexed Phase Locked
Loop transmitters, broadband design (88-108MHz). Design and selection
of VCOs, pre-scalers, and loop filters. Antenna design and
construction: 5/8ths vertical groundplane, 1/4 wavelength, and
dipoles. Compressor-limiter and Chebychev Low-pass filter design.
Microwave (MMIC) testing and tuning (2-18GHz). Design of
equalizers and filters. Linearity of Detector Logarithmic Video
Amplifiers. Temperature compensation networks.


You win a prize if you can guess where i last worked...

Your turn Tom...


Slick

Very impressive. You've designed 5/8s vertical ground planes,
1/4 wavelength [something or others, I guess] and dipoles.
Where are you working now? Did you go to Lowell?
73,
Tom Donaly, KA6RUH

Tdonaly wrote:
What's the radius of a virtual photon, Cecil?

From _Optics_, by Hecht: "When two electrons repel one another, or an
electron and proton attract, it is by emitting and absorbing virtual
photons and thereby transferring momentum from one to the other, ...
Virtual photons can never escape to be detected directly by some
instrument."
--
73, Cecil http://www.qsl.net/w5dxp



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