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.