Reflection Loss
 

"Richard Harrison" wrote
There really is no need to rename the ubiquituos SWR meter as Reg
has
recommended. This really requires no comment as it isn`t about to
happen.
=========================================

Richard,

Maybe you are right about no need to rename the SWR meter. It does
indeed indicate SWR when located at the correct place in the system,
it is correctly calibrated impedance-wise, and there is a line on
which it can be assumed an SWR exists.

But where the thing is located in 99.9 percent of occasions it
indicates nonsense. Where SWR on the antenna's feedline is concerned
it is totally misleading to novices, CB-ers, amateurs and
professionals alike. Hardly educational!

I have noticed a few references to TLI are beginning to appear. All
that's needed is a sensible Japanese, Chinese or Korean transceiver
manufacturer to face the facts and refer to TLI in an operating or
maintenance manual.

I know its sometimes difficult to learn a new word in a new way of
thinking but force yourself to comply with the obvious!

It's much easier than having to change to the Metric System. The same
economies apply.
----
Reg, G4FGQ.

Reflection Loss
 

Reg Edwards wrote:
I have nothing from Kraus. I know of him only from the frequency at
which he is referred to by bible worshippers on this newsgroup.

Reg, for anyone who is interested, "Antennas for All Applications",
3rd edition, by Kraus and Marhefka, ISBN 0-07-232103-2, is available
"new" or "as new" from the following source for $30. It would be nice
if everyone on this newsgroup would spring for one. It comes close to
being the best $30 that I ever spent on a book.

http://www.abebooks.com/

http://dogbert.abebooks.com/servlet/...072321032&x=54

--
73, Cecil http://www.qsl.net/w5dxp

Reflection Loss
 

On Mon, 6 Mar 2006 16:58:03 +0000 (UTC), "Reg Edwards"
wrote:

I have read about B,L & E. They are the famous trio who left the site
without bothering to measure ground resistivity.

This is the makings of Victorian Melodrama, because they also did not
measu
the altitude;
the humidity;
the phase of the moon;
the date of the Paschal moon;
the height of the tide in Tasmania;
the frequency of eruptions from Mt. Etna;
the red shift emitted from the star Betelgeuse.

Of course, Reggie, I will leave you with the last half dozen responses
to flesh out this list.

73's
Richard Clark, KB7QHC

Reflection Loss
 

On Mon, 6 Mar 2006 04:49:53 -0600, (Richard
Harrison) wrote:



Richard,

You originally stated:

On page 99 of Terman`s 1955 edition of "Electronic and Radio
Engineering" (my textbook was an earlier edition) is found the formula
to convert the reflection coefficient into SWR or vice versa. These
two parameters are innexorably locked together by formulas (4-22a) and
(4-22b).

You are squirming away from the accuracy of your assertion that Terman
calculates reflection coefficient from SWR, ie the "or vice versa" in
your statement.

The reflection coefficient is a complex number with magnitude and
phase, as you acknowledge when you later say "It is true that the
reflection coefficient is a vector ratio of the reflected voltage to
the incident voltage at the load".

In formula 4-22b of my copy of Terman, the term on the lhs is |rho|,
which is the magnitude of the reflection coefficient.

No, you cannot calculate the reflection coefficient from SWR alone,
but you can calculate the magnitude alone, but that is less
information than the reflection coefficient.

To illustrate, and as you know, the reflection coefficient at a point
can be used with the line propagation constants to calculate the
impedance at another point on the line. You cannot do that with the
magnitude of the reflection coefficient.

You have misrepresented Terman, he does not calculate the reflection
coefficient from SWR (at least not in my copy).

Owen
--

Reflection Loss
 

Owen Duffy wrote:
"In formula 4-22b of my copy of Terman, the term on the lhs is Irhol
which is the magnitude of the reflection coefficient."

In my copy, 4-22b gives the "absolute value" of the reflection
coefficient (it is embraced with bars) which I believe means the
"absolute value" of a number or a symbol without reference to its
algebraic sign.

(4-22b):
+or- reflection coefficient=
SWR-1 / SWR+1

These formulas, (4-22a) and 4-22b) aren`t just theory. They are
constantly put to use. A derivation which uses the sq rt of the ratio of
refllected power to forward power for the reflection coefficient appears
on page 23 of my Bird Model 43 Directional Thruline Wattmeter Manual.:
SWR = 1+reflection coefficient / 1-reflection coefficient
(Same as 4-22a)

Transmission lines are special because they enforce Zo. That is, in
either direction of travel, when you apply a voltage to the low-loss
line, the current which results is locked in-phase with the applied
voltage. In other words, Zo is a resistance.

Best regards, Richard Harrison, KB5WZI

Reflection Loss
 

I have just had several glasses of Australian Zonte's Footstep wine.
I can recommend it. Its name can be traced back to a marsupial which
replaced the dinosaurs. .............

Maybe so, but the name gives me the image of a bunch of VK's stomping
around on a bunch of grapes with their bare feet. Just hoped they
washed
them first... "the feet, more importantly than the grapes" :/
MK

Reflection Loss
 

On Mon, 6 Mar 2006 20:20:14 -0600, (Richard
Harrison) wrote:

Owen Duffy wrote:
"In formula 4-22b of my copy of Terman, the term on the lhs is |rho|
which is the magnitude of the reflection coefficient."

In my copy, 4-22b gives the "absolute value" of the reflection
coefficient (it is embraced with bars) which I believe means the
"absolute value" of a number or a symbol without reference to its
algebraic sign.

(4-22b):
+or- reflection coefficient=
SWR-1 / SWR+1

Richard, you seem to be dealing with reflection coefficient as a real
number when in fact it is a complex number. Your definition of |rho|
is inadequate when rho is complex.

Terman actually says in the preceding text "The standing wave ratio S
is one means of expressing the magnitude of the reflection
coefficient; the exact relationship between the two is..."

Your statement "On page 99 of Terman`s 1955 edition of "Electronic and
Radio Engineering" (my textbook was an earlier edition) is found the
formula to convert the reflection coefficient into SWR or vice versa.
These two parameters are innexorably locked together by formulas
(4-22a) and (4-22b)." is wrong where it says "convert the reflection
coefficient into SWR or vice versa" in respect of the "vice-versa"
because you ignore the fact that the reflection coefficient is a
complex quantity, and that the "magnitude of reflection coefficient"
is not the same thing as "reflection coefficient. You cannot calculate
the reflection coefficient from the SWR (except of course the special
case where SWR=1).

You have cited Terman in support of your own loose words, but Terman's
words are more carefully chosen and correct, yours are not, and the
Terman reference does not support your misconception at all.

Owen
--

Reflection Loss
 

Owen Duffy wrote:
"Richard, You seem to be dealing with reflection coefficient as a real
number when in fact it is a complex number."

I plead guilty.

Best regards, Richard Harrison, KB5WZI

Reflection Loss
 

Richard Harrison wrote:

Owen Duffy wrote:
"Richard, You seem to be dealing with reflection coefficient as a real
number when in fact it is a complex number."

I plead guilty.

OTOH, some text I have in my library treats 'rho' as a magnitude
and 'gamma' as the complex reflection coefficient.
--
73, Cecil http://www.qsl.net/w5dxp

Reflection Loss
 

On Tue, 07 Mar 2006 18:04:50 GMT, Cecil Moore wrote:

Richard Harrison wrote:

Owen Duffy wrote:
"Richard, You seem to be dealing with reflection coefficient as a real
number when in fact it is a complex number."

I plead guilty.

OTOH, some text I have in my library treats 'rho' as a magnitude
and 'gamma' as the complex reflection coefficient.

Irespective of the symbol that may be used, and there are
unfortunately many schemes, the reflection coefficient is a complex
quantity.

Owen
--