"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

For those who have forgotten how or have never measured SWR.

Two separate voltage measurements are needed at two different places along
the line.
Slide the voltmeter along the line until a maximum is found.
Remember the reading, Vmax.
Slide the meter along the line again until a minimum is found.
Remember the reading, Vmin.
Before you forget, divide Vmax by Vmin.
You are left with a single number.
It has no dimensions.
It is the TRUE swr.

NOTE: In the above description and calculation there is no mention of Zo,
terminating impedance, source impedance, reflection coefficient, forward
power, reflected power, reflected volts, reflected current, Smith charts, or
conjugate matches. All these things are superflous to the determination. No
information other than the two voltage measurements is needed.

All other methods which purport to measure swr require injection of
additional information. And assumptions form an essential part of the
process. They can hardly be called swr measurements. Particularly when
they can indicate it on non-existent lines.

Reg Edwards wrote:
For those who have forgotten how or have never measured SWR.


Hang on, Reg - didn't you spend your career working on VLF cables that
went under the ocean?


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

Reg Edwards wrote:
All other methods which purport to measure swr require injection of
additional information. And assumptions form an essential part of the
process. They can hardly be called swr measurements.

They can be called indirect (calculated) SWR measurements
and assumptions indeed do form an essential part of the
process. That's not at all unusual for indirect measurements.

Particularly when they can indicate it on non-existent lines.

One of the assumptions is that a transmission line exists. If
a transmission line doesn't exist, the measurement conditional
assumptions are violated, and the actual values may not be
the desired or expected results. Happens all the time with
various measuring instruments.
--
73, Cecil http://www.qsl.net/w5dxp



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On Sat, 4 Sep 2004 14:08:53 +0000 (UTC), "Reg Edwards"
wrote:

NOTE: In the above description and calculation there is no mention of Zo,
terminating impedance, source impedance, reflection coefficient, forward
power, reflected power, reflected volts, reflected current, Smith charts, or
conjugate matches. All these things are superflous to the determination. No
information other than the two voltage measurements is needed.

Hi All,

No mention merely means there is no offer of accuracy (not very
important, eh what?). These two measurements (repeated at intervals)
can reveal a SWR that varies along the length of the line like a snake
- UNLESS of course, you DO observe unmentionables like Load reflection
co-efficients and Source reflection co-efficients. As such, a
description of how not to measure SWR, but rather how to exhibit error
if you perchance have the misfortune of having a transmitter that is
unmatched to a 50 Ohm transmission system whose load is in fact
mismatched also.

Need I point out that if both ends are matched - what's the point in
measuring SWR? ;-)

73's
Richard Clark, KB7QHC

Richard Fry wrote:
"Or the meter scale could just have three zones: Good - ? - Bad,---."

As I recall, such a meter display used to be called an "English Scale".
This may appeal to Reg.

Best regards, Richard Harrison, KB5WZI

Somebody said, I can't tell who (or is that whom?):
Reg,
I know you 'have a thing' about the SWR meter not measuring SWR.
I have an ohm-meter. It doesn't 'measure' ohms. It actually measures
current.
How many 'meters' actually measure what we say they measure?
Speedometer?

So these used to measure magnetic drag on a conducting cup of a transmission
output monitoring rotary cable and therefore should be called a
Mdoaccoatomrc-o-meter

Flow-meter?

Lets see. One versions I am familiar with measures the number of free
balls passing a given point in a circulary disposed tube while following the
movement of a liquid and therefore is a:
Fbpagpiacdt-o-meter, I guess..


Odometer?
And this turky measures the revolutions of the first thingy.


Kill-ommeter? (as pronounced by thickies - ugh!)

Don't you mean Kill-o-meter?

Woops! Does anyone sell these meters???

Besides we say cent-a-meter


And... and... an ohm-meter is really an "incorrectly calibrated am-meter",
as is a volt-meter. Then is an am-meter a "magnetic field produced by a
coil", or an MFPBAC-o-meter ???

Methinks thou splitteth hairs.

Well...

How come we say ther-mom-eter and speed-om-eter and o-dom-eter and
comp-tom-eter, but we don't say ohm-om-eter, volt-om-eter nor am-om-eter...

And how come we say "how come" when we mean "why do"????
And why is a "K" 1000 in our world and a "K" 1024 in the digital world
except for hard drives where a meg is 1,000,000....

....and why am I here... for those who like rhetoricals.

Someone needs something serious to think/talk/post about.

Hmmmm. Me thinketh there needs to be a troll-o-meter, or would it be a
troll-om-eter...
73

Boy! spell check sure didn't like this post!
--
Steve N, K,9;d, c. i My email has no u's. and no meters either.