"Reg Edwards" wrote (clips):
Yet another reason why the so-called swr meter does not
measure swr is because there is no transmission line
(between meter and transmitter) on which to measure it.
SWR on it cannot not exist.

The indication displayed by that meter is the result of the match of the
transmission line and antenna connected to the output of the transmitter to
the value for which the meter was designed and calibrated. Certainly it is
possible for SWR to exist in this RF system in normal use, and the meter
measures its value.

My objection to current practice arises because the invalid
name of the instrument, plus all the arguments which arise
in futile attempts to justify it, cause nothing but emotional
confusion amongst novices and old-wives alike.

The generic function of this meter is to measure the degree of match between
a source and a load. It is not a direct measure of SWR. When properly
designed, it is a measure and comparison of voltages developed by the
incident and reflected power in the system as they pass a sample point.

There may not be enough transmission line in the RF system for the standing
wave pattern itself to develop on it fully. It doesn't matter. The ratio
of forward to reflected power in the system will be the same as if there WAS
enough line, and that is what the meter measures.

The meter could be calibrated in units of return loss, reflection
coefficient, or SWR -- all of which have corresponding equivalents. A
return loss of 26.45 dB = 4.76% reflection coefficient = 1.1:1 SWR, for
example.

The historical convention for this meter is to calibrate its display in
units of SWR. Or the meter scale could just have three zones: Good - ? -
Bad, which would do away with all these troublesome technical terms and the
objections they elicit from some (nudge, nudge). No offense.

RF






Ian, without wishing to cause the slightest offence, I'm afraid your long,
ingrained, aquaintance with the old-wives' tales surrounding swr meters is
preventing you (and others) from seeing things from a different point of
view.

The instrument is just a 4-arm RF resistance bridge, the arm subject to
variation being the input impedance of the transmission line to the
antenna
which can be any Zo you like. The other 3 arms are fixed.

The 'meter' merely indicates whether or not the input impedance of the
line-to-the-antenna is some special value of ohms (usually 50) because
that
is the desired transmitter load.

It won't, and cannot even, tell you what the value of that special value
actually is except under the very exceptional condition that it is exactly
correct.

And it tells you absolutely nothing else about what exists or is going on
in
the station unless you deduce and add to it what you already know by other
means anyway.

My objection to current practice arises because the invalid name of the
instrument, plus all the arguments which arise in futile attempts to
justify
it, cause nothing but emotional confusion amongst novices and old-wives
alike.

So why not just change the name to TLI (Transmitter Loading Indicator) and
all the confusion and arguments will cease. Novices will no longer have to
be re-educated about the true meaning and relevance of swr.

Or YOU can choose a new name if you wish and take the credit for it.

No circuit changes are needed. ;o)
---
Regards, Reg, G4FGQ