Richard Fry wrote -
The generic function of this meter is to measure the degree of match
between
a source and a load.

--------------------------------------------------------

Exactly! So let's call it a TLI. Which is what it actually is. Abolish
the source of confusion and the arguments on what it does.

Of what use is the swr to anybody anyway, even when you think you know what
it is? What do you do with it? What does it tell you that you don't
already know?
---
Reg

In message , Reg Edwards
writes
Richard Fry wrote -
The generic function of this meter is to measure the degree of match
between
a source and a load.

--------------------------------------------------------

Exactly! So let's call it a TLI. Which is what it actually is. Abolish
the source of confusion and the arguments on what it does.

Of what use is the swr to anybody anyway, even when you think you know what
it is? What do you do with it? What does it tell you that you don't
already know?
---
Reg



Call it an RLR meter, which is what it IS really measuring.
Ian.
--

Ian Jackson wrote:
Call it an RLR meter, which is what it IS really measuring.

How about an "SVI", Superposed Voltage-sample(+/-)Current-sample,
named for the math function that it is performing?
--
73, Cecil http://www.qsl.net/w5dxp


-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

"Reg Edwards" wrote:
Of what use is the swr to anybody anyway, even when
you think you know what it is? What do you do with it?

You strive to minimize it.

What does it tell you that you don't already know?

You won't know anything about the degree of match between a source and its
load without a means of measuring it. It doesn't matter whether we state
the result of the measurement in units of SWR, return loss or as a
reflection coefficient -- they all give the same information, and allow the
same action to be taken as a result.

To be accurate and valid, none of these units requires measurements to be
taken with some discrete length of transmission line between the source and
the load -- including SWR.

RF

Richard Fry wrote:
"It doesn`t matter whether we state the result of measurement in units
of SWR, return loss, or as a reflection coefficient -- they all give the
same information -- ."

Correct. The units above are fungible. All are an expression of the
mismatch of a load to the Zo of the transmission line.

With a Bird wattmeter, the reflection coefficient (rho) is the sq. rt.
of the reflected power divided by the forward power.

SWR = 1+rho / 1-rho

Return loss in dB = 20 log (rho)

Return loss in dB = 10 log (Ref.Pwr./Fwd.Pwr.)

Rho = (ZL/Zo)-1 / (ZL/Zo)+1

None of the expressions above include the source Z, therefore it does
not apply.

Best regards, Richard Harrison, KB5WZI

"Reg Edwards" wrote

let's call it a TLI. Which is what it actually is. Abolish
the source of confusion and the arguments on what it does.
_____________

Afterthought... if you call it a TLI, is that really less confusing? The
term "Transmitter Loading Indicator" could apply to a way to display the
amount of power at the tx output terminals, and show nothing of the quality
of the load that is dissipating that power (e.g., the degree of match
between the source and the load).

RF

On Fri, 3 Sep 2004 14:14:57 +0000 (UTC), "Reg Edwards"
wrote:

|Richard Fry wrote -
| The generic function of this meter is to measure the degree of match
|between
| a source and a load.
|
|--------------------------------------------------------
|
|Exactly!

Not!

The source plays no role at all. The degree of match that is
indicated is that between the line (or system Zo) and the load Z.

A 50 ohm instrument with a 50 ohm termination shows a reflection
coefficient (or whatever mathematical equivalent you want to use) of
zero regardless of the source impedance.


|So let's call it a TLI.

Let's don't. That's just more bafflegab. Suppose the source impedance
is 25 ohm and the load is 50 ohm. By this new monstrosity of a
definition, the source should be delighted when the "transmitter
loading indicator" says---well---I'm not sure what it says, but I
think the desired number is either 0 or 1. And another source
(transmitter) with a source Z of 100 ohm should be equally happy.
Right?


|Which is what it actually is. Abolish
|the source of confusion and the arguments on what it does.


I'm all for abolishing the confusion too, so why did you add to it?

"Wes Stewart" wrote (clip):

"Reg Edwards" wrote:
|Richard Fry wrote -
| The generic function of this meter is to measure
| the degree of match between a source and a load.
|--------------------------------------------------------
|Exactly!

Not!
The source plays no role at all. The degree of match that is
indicated is that between the line (or system Zo) and the load Z.
A 50 ohm instrument with a 50 ohm termination shows a reflection
coefficient (or whatever mathematical equivalent you want to use) of
zero regardless of the source impedance.
__________

I wrote "BETWEEN a source and a load," not OF the source
and a load. There is a difference.

RF

Richard Fry wrote:
"Wes Stewart" wrote (clip):

"Reg Edwards" wrote:
|Richard Fry wrote -
| The generic function of this meter is to measure
| the degree of match between a source and a load.
|--------------------------------------------------------
|Exactly!

Not!
The source plays no role at all. The degree of match that is
indicated is that between the line (or system Zo) and the load Z.
A 50 ohm instrument with a 50 ohm termination shows a reflection
coefficient (or whatever mathematical equivalent you want to use) of
zero regardless of the source impedance.
__________

I wrote "BETWEEN a source and a load," not OF the source
and a load. There is a difference.

The only difference between those two terms is that "match between" is
normal and grammatical technical usage; and "match of" ain't neither.

Wes is correct. What the meter measures is the match (expressed as
reflection coefficient, SWR, whatever) between the system Zo for which
that meter was designed and calibrated, and the load Z.

The meter measures nothing that involves the source, except the level of
RF that it supplies. It does not respond in any way whatever to the
source impedance.


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

"Ian White, G3SEK wrote
The meter measures nothing that involves the source, except
the level of RF that it supplies. It does not respond in any way
whatever to the source impedance.
_____________

Not that I said it did in my part of the thread, but nevertheless the above
statement is not strictly true. In the case where the source Z of the tx PA
does not match its load Z (which is typical), power reflected from the load
mismatch will at least partly be re-reflected from the PA -- which then
contributes to the power sensed by a "wattmeter" in the output path.

RF