On 14 Aug 2003 08:30:53 -0700, (Tom Bruhns) wrote:

"Ian White, G3SEK" wrote in message ...
...
The subject is why SWR meters might read differently with different
lengths of coax. Your statements about mismatch uncertainty are true,
but not relevant.

Somewhere in all this mess, I believe RC posted that the OP's
originally posted observations supported his claim (that source
impedance affects line SWR), but yet when I go back and read the OP's
observations, they are that the POWER delivered to the load changes
significantly with line length and the measured line SWR DOES NOT
change noticably.

It seems to me that the OP's observations directly support that the
line SWR does not change with changes in source impedance: if the
transmitter output impedance is not equal to the line impedance, the
additional line can be though of as lumped with the transmitter and
where it connects to the original length would be the point where the
source impedance would be measured...and it would have changed
significantly with added line, while the SWR did not.

Cheers,
Tom

Hi Tom,

Thanks for actually looking. You are indeed correct in your statement
about the "small" variation of SWR:
SWR DOES NOT change noticably.
This, too, is consistent with the data I have offered. Casual
benchwork is as likely to reveal that as not. This is to say that no
real examination was originally performed, it was discovered by
accident (the portents of the variation of Power were more
distracting) and the readings were discarded as, perhaps, simple
statistical fluctuation. If through the sheer chance of opportunistic
luck in drawing different line lengths into the original posting,
those values may have been far more significant. If I had trimmed my
data to a very short interval, it would have matched his. The
variation follows a sine curve shape (if anyone had actually viewed
the data, this would be obvious) and you can take several readings
along the slope with alarm, or several along the crest to
indifference. This simply reveals that the original posting lacked
many essential details, but contained many confirmatory ones.

This does not change the fact that as a subset of my data, that it
lacks supporting my results simply because it does not go to the
breadth nor depth of my study. I in fact offered three significant
quotes of his original observations made that are classic indicators
of Mismatch Uncertainty. The simple point of that issue is that you
cannot measure Power with any promise of accuracy when placed between
two discontinuities. Unless you can describe all paths. This is a
staple of simple wave interference. It necessarily follows that if
you cannot determine Power due to this indeterminacy, you have no
chance of determining SWR (you can certainly offer a reading and go on
about life blithely unaware).

Simply put, I don't see anyone here willing to put their "faith" to
the test; and I am the only one here with my skin in the game. I am
far more likely to accept error through honest effort equal to mine
that demonstrates it. But critics to this point have not only refused
to step up to the bench, but they have also denied the argument
through aggressively ignoring my methods and their results. I observe
far more reading of my comments here, than with that one posting. As
such, it is more than obvious that entertainment is the driving force
for this criticism, not technical review.

73's
Richard Clark, KB7QHC