Reg Edwards wrote:

But where have you hidden this remarkable transmission line which is long
enough to mug and hoodwink so-called SWR meters?

It does not exist!

Most resonant 50-ohm-coax-fed dipoles would meet those requirements.
All that is needed is for it to be long enough to force the forward
V/I ratio to Z0. Given the small diameter of a piece of coax compared
to a wavelength at HF, it doesn't seem that it take a very long length.
Waveguides may be a different story.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

On Sat, 04 Oct 2003 10:46:41 -0500, Cecil Moore
wrote:

Reg Edwards wrote:

SWR meters are designed to operate and provide indications of SWR, Rho, Fwd
Power, Refl.Power, on the ASSUMPTION that the internal impedance of the
transmitter is 50 ohms.

I believe that to be an incorrect statement, Reg. The assumption is that
a Z0 of 50 ohms exists and the transmission line is long enough to force
the ratio of V/I to be 50 ohms for the forward wave and the reflected wave.
The phase between the forward voltage and current is assumed to be zero.
The phase between the reflected voltage and current is assumed to be zero.
Given all those assumptions, the internal impedance of the transmitter is
irrelevant. I'm not saying all those assumptions are always met.

Sorry, Cecil, the phase between reflected voltage and current is always 180
degrees, not zero. If it were not for this phenomenon the standing wave would
not be established as forward and reflected waves of both voltage and current
pass through each other otherwise undisturbed.

Walt, w2du

Put a 50 ohm dummy load on an SWR meter and feed it with a transmitter
of unknown source impedance. The SWR meter will always read 1:1 because
the dummy load forces the V/I ratio to be 50 no matter what the source
impedance. That's what the 50 ohm characteristic impedance of the
transmission is supposed to do to make the source impedance irrelevant.

PS: In the whole of his excellent 236-page exceedingly comprehensive
volume, Chipman, in 1969, makes not the slightest mention of SWR meters.

In 1969, virtually all ham transmitters had an adjustable pi-net output
so an SWR meter was not needed. When I started out as a ham in the 1950's,
just as many hams used 75 ohm coax as used 50 ohm coax, maybe more. The
pi-net output of a typical ham transmitter back then didn't care what the
Z0 was. I didn't own an SWR meter until the 1980's when I bought an IC-745.

In 1969, the "antenna tuner" was built into the transmitter. If wide-
range antenna tuners were built into transmitters today, there would be
little need for the SWR meter. I don't know of anyone who puts an SWR
meter between an SGC-230 and the antenna.

Walter Maxwell wrote:
Sorry, Cecil, the phase between reflected voltage and current is always 180
degrees, not zero.

Yep, I know better, I just mis-spoke. Did you know that there is no
such convention for light? It's Kirchhoff's current convention that
dictates a 180 degree phase between reflected voltage and reflected
current. EM light doesn't follow Kirchhoff's convention.

For EM light, there is no phase shift in the reflection if the index
of refraction is higher. If the index of refraction is lower, there
is a 180 degree phase shift in both E and H fields.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

Reg Edwards wrote:
But where have you hidden this remarkable transmission line which is long
enough to mug and hoodwink so-called SWR meters?

It does not exist! Your argument falls flat at the start.

I don't know the answer to this question but perhaps some lurker does.

On each side of my SWR meter, I have three feet of RG-400 coax. The
spacing between conductors must be about 0.1 inches. With a spacing
of 0.1 inch between conductors in the coax, what length of coax is
required to force a V/I ratio of 50 ohms? The ratio of 3 feet to 0.1
inches is 360. I suspect that three feet is plenty long enough.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

"Richard Clark" wrote in message
...
....................................
Richard, how can you possibly believe that the output impedance of the
source
has any effect on the SWR on a transmission line?

Stephen Adam of HP using Beatty describes it quite well. The data you
have by email and has been posted here demonstrates it equally well.
It takes no more than two resistors and a length of line to confirm or
deny. My data confirms it, absolutely no one has offered negative
evidence, simply denials...................................
73's
Richard Clark, KB7QHC

Richard,

Please humor me. If the source impedance has an effect on SWR, surely an
equation exists that spells that out. Perhaps you can divulge it for
everybody.

Tam/WB2TT

"Reg Edwards" wrote in message
...

Reg, that can't possibly be you. Someone has hijacked your e-mail.

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

Ian, it IS me! Please calm yourself.

Let me put what I said into somewhat different words.

SWR meters are designed to operate and provide indications of SWR, Rho,
Fwd
Power, Refl.Power, on the ASSUMPTION that the internal impedance of the
transmitter is 50 ohms. It makes the same INCORRECT assumption as a lot
of
people do. This should not be surprising because it was people who
designed
it.

So SWR meters nearly always give FALSE indications about what actually
exists.

Perfectionists may be upset at the repercussions of this alarming
statement.

PS: In the whole of his excellent 236-page exceedingly comprehensive
volume, Chipman, in 1969, makes not the slightest mention of SWR meters.
----
Reg, G4FGQ

Reg,
The SWR meter knows only by how much the load deviates from 50 Ohms.
Somebody has very cleverly interpreted this, and calculated how the meter
scale should be labeled. Actually, the SWR/Power meter has information that
is not displayed. For instance, for a 2:1 SWR it has the needed information
to differentiate between a 25 and 100 Ohm koad, but to display this
information would require adding extra parts

BTW, I did force the SWR meter to see a different source impedance. There
was no difference in SWR readings for either the 1:1 or 2:1 case.

On Sat, 04 Oct 2003 10:08:40 -0500, Cecil Moore
wrote:
Here's a quote from Chipman.
....
Would you like to pose a complex Z0?

Hi Cecil,

What for? Random selections of quotation are hardly the basis for
discussion. -Eh- let me take that back, it seems it's the ONLY basis
for discussion.

I note, as posed before, that Ian who "might" hold a copy of Chipman
has yet to respond to my points about its contents. My having offered
chapter and verse, it would seem less than a monumental task to simply
turn to the page and verify my selection, or refute Chipman's
statements. Those who hold him dear seem the least likely to respond
to his teachings.

73's
Richard Clark, KB7QHC

On Sat, 4 Oct 2003 14:26:37 -0400, "Tarmo Tammaru"
wrote:
Richard,

Please humor me. If the source impedance has an effect on SWR, surely an
equation exists that spells that out. Perhaps you can divulge it for
everybody.

Tam/WB2TT


Hi Tam,

I could, but I won't. If you wish to be humored, email me as has
Walt. That venue is far more productive than me providing yet another
citation, its quote, its elaboration, its demonstration at the bench
with data, to only observe it won't "change my mind" sclerosis
mentality exhibited in this forum's sneer review.

I have offered several such matters direct to the point to have those
who could respond from actual verification by observing it in their
copy simply vanish from the debate. As I recall, you did exactly the
same thing with a Motorola application note about source Z that you
never confirmed or denied after introducing it as evidence against my
position.

As for humoring, I find that in the obvious logical disconnects and
exhibiting it here.

73's
Richard Clark, KB7QHC

SWR meters are designed to operate and provide indications of SWR, Rho,
Fwd
Power, Refl.Power, on the ASSUMPTION that the internal impedance of the
transmitter is 50 ohms. It makes the same INCORRECT assumption as a lot
of
people do. This should not be surprising because it was people who
designed
it.

So SWR meters nearly always give FALSE indications about what actually
exists.

------------------------------------------------------
Reg,

BTW, I did force the SWR meter to see a different source impedance. There
was no difference in SWR readings for either the 1:1 or 2:1 case.

------------------------------------------------------

Tarmo,

And of course, as you and I know, on whatever line there is between the
meter and transmitter, the swr is neither the indicated 1:1 nor 2:1 because
the input impedance looking back towards the tranmitter is not the assumed
50 ohms. Both readings are false, even meaningless. There may in fact be no
standing waves to measure.

To avoid confusing novices and budding engineers, retarding education,
rename the meter the TLI (Transmitter Loading Indicator) which is what it
really is.
----
Reg, G4FGQ

Richard Clark wrote:
I note, as posed before, that Ian who "might" hold a copy of Chipman
has yet to respond to my points about its contents.

I have ordered a copy. From what I have read of Chipman so far,
everything can be explained by achieving a conjugate match at
one point on the transmission line when the reactance looking
in either direction is at a maximum. This is simply a resonance
effect. Here's a bench experiment that might shed some light
on this problem.

source--50 ohm coax--(-j500)--SWR meter--(+j500)--50 ohm coax--50 ohm load

There is a localized high reactive energy exchange through the SWR meter
between the capacitance and the coil but nowhere else on the transmission
line. That has got to have an effect on the SWR reading which is probably
not good. What, exactly, is the big deal? It is just another distributed
circuit problem.
--
73, Cecil http://www.qsl.net/w5dxp



-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----