Reg Edwards wrote:

Makes a change from so-called SWR meters.

Ah Reggie!

Hardly, SWR was the second most considered technical hurdle in the
development of RADAR.

73's
Richard Clark, KB7QHC

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

Ah Rich!, Yet again you deliberately distort my meaning in your
amusing game of 0ne-Upmanship.

For the benefit of lurkers, there's a great difference between meters
which purport to measure SWR at HF, but do no such thing and tell
lies, and probes inserted in waveguides at 3 GHz which tell the truth.
----
Reg.

Sorry, I don't see any difference between making voltage measurements
with a directional coupler and calculating SWR through meter calibration
and making voltage measurements on a slotted line and calculating SWR
with a calculator or pencil and paper.

Best I can tell is you are saying there is no such thing as a SWR meter.

That's like saying there is no such thing as an airspeed meter in an
airplane; the meter really measures air impact pressure.

If that is your point, so what?

--
Jim Pennino

Remove .spam.sux to reply.

Jim,

To measure SWR on the line it is necessary to place the SWR meter at
the antenna end of the line. Even then it gives the correct answer
only when the line impedance is 50 ohms.

But the SWR meter is always placed immediately adjacent to the
transmitter. Whatever the meter indicates it is not SWR because there
is no line on which to measure it. The meter is telling lies.

The meter indicates only whether or not the transmitter is loaded with
a resistance of 50 ohms. Which is ALL you want to know. It tells you
nothing more and nothing less.

This is, of course, a very valuable function of the instrument. But
it is NOT behaving as an SWR meter. Its name should be changed to
Transmitter Loading Indicator (TLI).

To use the name "SWR meter" and to imagine it is actually measuring an
SWR is seriously misleading and is a source of confusion about what is
really going on.

It is why there are perpetual arguments and misunderstandings about
SWR, tuners and related matters on this newsgroup and in every other
place.

Change the name to TLI, which is what it really does. Novices will not
be lead astray, clear thinking will prevail, false ideas will not take
root to remain embedded for the remainder of one's radio career.

Air pressure indicators instead of airspeedometers are OK because air
pressure actually exists.

SWR meters are NOT OK because there is no line for SWR to exist on.
(At least not where the meter is imagined or supposed to measure it.)

Makes a change from cavity magnetrons.
----
Reg.

On Sun, 25 Sep 2005 03:44:00 +0000 (UTC), "Reg Edwards"
wrote:

Ah, Reggie, and Richie----

You two ought to go on the road together--your humor beats Bob Hope's hands
down. You'd have em laughing their guts out in the aisles!

Walt, W2DU

Reg Edwards wrote:
Jim,

To measure SWR on the line it is necessary to place the SWR meter at
the antenna end of the line. Even then it gives the correct answer
only when the line impedance is 50 ohms.

Well, duh.

Anyone that doesn't know that SWR is with reference to a stated
impedance or that SWR is influenced by the characteristics of a
real transmission line just isn't paying attention.

But the SWR meter is always placed immediately adjacent to the
transmitter. Whatever the meter indicates it is not SWR because there
is no line on which to measure it. The meter is telling lies.

Errr, no, the meter is telling what it sees at the point of measurement.

If the measurer is so opaque that he/she doesn't take line influences
into account, it is hardly the fault of the measuring instrument that
what is reported is not the SWR of the antenna at the specified
impedance.

The meter indicates only whether or not the transmitter is loaded with
a resistance of 50 ohms. Which is ALL you want to know. It tells you
nothing more and nothing less.

Basically true given the stated conditions, and all that is probably
of interest for the average ham.

This is, of course, a very valuable function of the instrument. But
it is NOT behaving as an SWR meter. Its name should be changed to
Transmitter Loading Indicator (TLI).

Uttern nonsense; the instrument is still behaving as a SWR meter but
the user is not applying it per spec and not correcting measurement
error caused by line position.

By this logic we have a lot of names to change. For starters:

PAM has to change the name of their cooking spray to: Teenage looser
get high in a can.

Screwdriver manufacturers have to change the name of their product
to: General prying instrument and paint can lid removal tool.

You may add others.

To use the name "SWR meter" and to imagine it is actually measuring an
SWR is seriously misleading and is a source of confusion about what is
really going on.

Nonsense, the meter is always measuring SWR but the user is obviously
not measuring the SWR that would be seen at the end of the line.

You can't fault the instrument for it's misuse by the ignorant.

What would you call a low impedance voltmeter used by some nimrod
to measure voltage in a high impedance circuit?

It is why there are perpetual arguments and misunderstandings about
SWR, tuners and related matters on this newsgroup and in every other
place.

That is probably true since most people are opaque as to what goes
on on a real transmission line, but not everyone is.

Change the name to TLI, which is what it really does. Novices will not
be lead astray, clear thinking will prevail, false ideas will not take
root to remain embedded for the remainder of one's radio career.

Clear thinking would demand that the influences of a real line on the
observered SWR at an arbitrary point be explained.

Air pressure indicators instead of airspeedometers are OK because air
pressure actually exists.

Non sequitur; SWR actually exists. Getting an accurate measurment is
another issue and a matter of education.

SWR meters are NOT OK because there is no line for SWR to exist on.
(At least not where the meter is imagined or supposed to measure it.)

Nonsense.

Makes a change from cavity magnetrons.

More nonsense and not even a sentence.

About the only difference between microwave and HF is that it is a lot
easier to build a line, i.e. waveguide, that approximates a theoretical
ideal lossless transmission line for reasonable distances at microwave
than it is to build lossless coax as commonly used at HF.

All the theory remains the same.

Personally, I have never had any problem with understanding what it is
that a SWR meter displays.

----
Reg.



--
Jim Pennino

Remove .spam.sux to reply.

Errr, no, the meter is telling what it sees at the point of
measurement.

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

But the meter is not seeing an SWR because an SWR does not exist.

Where is the 50-ohm transmission line on which the SWR is imagined or
supposed to lie?

As you are unable to answer that question, the remainder of your
argument (which, as I say, arises because of the SWR meter misleading
misnomer) falls flat on its face.

You are an intelligent person. I don't doubt you have no problems
with understanding what the so-called SWR meter really indicates. But
you didn't learn this from observations of the SWR meter - as you
already know it tells lies!

Just to reiterate, the so-called SWR meter indicates only whether or
not the load on the transmitter is a resistive 50 ohms. If it is not
50 ohms it will not tell you what it actually is. Not that you need to
know what it actually is because you will readjust your tuner, without
thinking about it, to make it equal to 50 ohms. Which corresponds to
no deflection of the meter needle.

The TLI is a very useful and valuable device. It does not lead
novices and old-wives (who ought to know better) into false ideas, or
cause confusion and misunderstandings within the amateur fraternity.
Professionals dismiss SWR for what it is worth anyway.

Goodby to SWR except on lines where it matters and where it can be
measured. Which, in practice, are very few.
---
Reg, G4FGQ.

Reg Edwards wrote:
Where is the 50-ohm transmission line on which the SWR is imagined or
supposed to lie?

On my system, there's a 50 ohm cable from the transceiver to
the input of the SWR meter and another 50 ohm cable from the
output of the SWR meter to the balun. Each of these cables
forces the ratio of the voltage to current in each of the
traveling waves to a value of 50 ohms. I have an in-line
Autek WM-1 and no tuner.
--
73, Cecil http://www.qsl.net/w5dxp

"Cecil Moore" wrote

On my system, there's a 50 ohm cable from the transceiver to
the input of the SWR meter and another 50 ohm cable from the
output of the SWR meter to the balun. Each of these cables
forces the ratio of the voltage to current in each of the
traveling waves to a value of 50 ohms. I have an in-line
Autek WM-1 and no tuner.
--
====================================

Cec,
You can't measure SWR on a line which is less than 1/4-wave long.
Preferably it should be as long as 1/2-wavelength to ensure the max
and min voltage points both occur on it.

But what do you do with the SWR when you have measured it? Of what use
it?

All anybody needs to know is whether the transmitter is terminated or
is not terminated with 50-ohms. This is very important.

And when describing to a novice how your station works there's no need
to mention SWR or reflections. They are quite unecessary complications
and can be dispensed with except perhaps for trolling on newsgroups.
----
Reg.

Reg Edwards wrote:
You can't measure SWR on a line which is less than 1/4-wave long.

Because your measurements are taken 1/4WL apart, your SWR value
will be in error for all feedlines except lossless ones.

SWR can be had at any point on a transmission line.
Measure the forward power and reflected power at any point.
SWR = [SQRT(Pfor)+SQRT(Pref)]/[SQRT(Pfor)-SQRT(Pref)]

The transmission line length must only be long enough such that
the V/I ratio is forced to the Z0 value. According to some pretty
smart guys I asked, that's about 2% of a wavelength.
--
73, Cecil http://www.qsl.net/w5dxp

Reg Edwards wrote:

"Cecil Moore" wrote

On my system, there's a 50 ohm cable from the transceiver to
the input of the SWR meter and another 50 ohm cable from the
output of the SWR meter to the balun. Each of these cables
forces the ratio of the voltage to current in each of the
traveling waves to a value of 50 ohms. I have an in-line
Autek WM-1 and no tuner.
--
====================================

Cec,
You can't measure SWR on a line which is less than 1/4-wave long.
Preferably it should be as long as 1/2-wavelength to ensure the max
and min voltage points both occur on it.

Total and absolute nonsense.

Where do you come up with this stuff?

snip arm waving speech

--
Jim Pennino

Remove .spam.sux to reply.

Reg Edwards wrote:
Errr, no, the meter is telling what it sees at the point of
measurement.

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

But the meter is not seeing an SWR because an SWR does not exist.

Nonsense.

Where is the 50-ohm transmission line on which the SWR is imagined or
supposed to lie?

In my personal case, there is 50 Ohm transmission line between the
transceiver and the SWR meter, then a length of line to a coax switch,
then several lines out to antennas.

You seem fixated on haveing some magical length of transmission line
being necessary for a SWR to exist. This is nonsense.

As you are unable to answer that question, the remainder of your
argument (which, as I say, arises because of the SWR meter misleading
misnomer) falls flat on its face.

You are an intelligent person. I don't doubt you have no problems
with understanding what the so-called SWR meter really indicates. But
you didn't learn this from observations of the SWR meter - as you
already know it tells lies!

Babble.

A SWR meter indicates what is. Knowing what the reading really means
is a matter of education, not veracity.

Just to reiterate, the so-called SWR meter indicates only whether or
not the load on the transmitter is a resistive 50 ohms. If it is not
50 ohms it will not tell you what it actually is. Not that you need to
know what it actually is because you will readjust your tuner, without
thinking about it, to make it equal to 50 ohms. Which corresponds to
no deflection of the meter needle.

With some education and multiple measurements, you can caluclate
the actual impedance if one desires.

What tuner? What makes you believe everyone has a tuner?

The TLI is a very useful and valuable device. It does not lead
novices and old-wives (who ought to know better) into false ideas, or
cause confusion and misunderstandings within the amateur fraternity.
Professionals dismiss SWR for what it is worth anyway.

The only one I see confused is you and professionals use SWR all the
time and in many systems it is extremely important.

Goodby to SWR except on lines where it matters and where it can be
measured. Which, in practice, are very few.

If one knows what they are doing, SWR can always be measured.

---
Reg, G4FGQ.



--
Jim Pennino

Remove .spam.sux to reply.