On Tue, 14 Oct 2003 09:09:20 -0500, Cecil Moore
wrote:
on an averaging RMS wattmeter.

Hi Cecil,

An average, by definition, cannot resolve a difference. Pointing out
such disconnects comes of your trying to force fit all problems to the
answer found on one xeroxed page.

This, also and again, shows to go you that introducing new variables
into an old issue you cannot resolve in the first place does little
for the new or the old.

73's
Richard Clark, KB7QHC

Cecil, W5DXP wrote:
"A flat system is conjugately matched, i.e. you see 50+j0 in one
direction and 50-j0 in the other direction."

Let`s simplify Cecil`s example. 50+j0 and 50-j0 can both be expressed as
50 ohms resistive. In other words they are the same.

A matched 50-ohm transmission line under maximum power transfer
conditions also has a 50-ohm source.

Conjugate matching is equivalent to maximum power transfer.

I agree with Cecil that: "A flat system is conjugately matched, i.e. you
see 50+j0 in one direction and 50-j0 in the other direction."

No matter where you slice the transmission line you see 50 ohms
resistive (volts and amps are in-phase) looking in either direction.
Nothing amiss except the word "conjugate" is superfluous in the special
case where the system is free from reactance.

Best regards, Richard Harrison, KB5WZI

I cleaned up the circuit somewhat. The current sense resistor is now 0.1
Ohm, and the signal is sampled through voltage follower opamps. So, there is
no shunt loading of any kind. I also increased the sampling rate.

For the example where the load is 50 - j400, and source is 0, I now get an
SWR of 66.3. Adding a source impedance of +j400 gives an SWR of 69.1. Since
I am doing a transient analysis, and reading amplitudes off the waveform,
this is about as close as I can get to having the two SWR readings be the
same. PF for the second case is now 86.25W and PR is 81.02, which gives a
net power close to the desired 5.0. The absolute numbers are clearly
meaningless; only their difference has any meaning.

I also tried a less extreme termination, 50 - j100. This gave an SWR of 5.7.
Conjugate matching at the source gave me 5.8. I think it is safe to say that
source impedance does not affect SWR.

I am going to try some other stuff, The simulator is perfectly happy if ,
for instance, I drive both sides of the meter with a 1KW signal. Either at
the same, or two different frequencies.

Tam/WB2TT
"Cecil Moore" wrote in message
...
Tarmo Tammaru wrote:
Now for Cecil 1. ZL = 50 - j400. VF=1.62, VR=1.56, SWR=53, PF=1.33W,
PR=1.24W.

Now for Cecil 2. ZL=50-j400, BUT ZS= 0 + J400. VF=11.2, VR=10.9,
SWR=73.7,
PF=64W, PR=60.6W. I am at such a high impedance here, that I suspect the
10K
sampling resistors are loading down the circuit somewhat. (I might try
100K
instead).

Note that there is absolutely nothing explicit in the circuit that has
anything to do with transmission lines. All components are perfect;
there
are no stray inductances or stray capacitors.

Chipman alludes to such a "phenomenon of resonance" in Chapter 10,
"Resonant Transmission Line Circuits". For instance, at a conjugate match
point where 100+j100 is seen looking in one direction and 100-j100 is
seen looking in the opposite direction, there seems to be a *localized*
exchange of extra energy between +j100 and -j100 that can adversely affect
the value indicated by an SWR meter placed between those two values.
--
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 Tue, 14 Oct 2003 14:51:38 -0400, "Tarmo Tammaru"
wrote:
I also tried a less extreme termination, 50 - j100. This gave an SWR of 5.7.
Conjugate matching at the source gave me 5.8. I think it is safe to say that
source impedance does not affect SWR.

Hi Tam,

From the sublime to the ridiculous. The SWR of what? Where? :-)

A transmitter is loaded with two components and a meter placed between
them - woohah! Using a SWR meter inappropriately is not proof of
measuring SWR. More sense could be found in measuring the
distribution of tea leaves.

The mythical lurkers should note all the effort that goes into a
perversion of a vastly simpler exercise that could be conducted easily
at the bench; and the reason for not going to the bench? Some infer
too hard (by lack of effort); others explicitly state it doesn't
matter (through reams of virtual pages gusting on about its
inconsequence); and yet others deferring it with excuses it demands
too much time for the effort.

But it does have its amusing moments, and I guess when all is said and
done, that counts for something.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote in message
...

The mythical lurkers should note all the effort that goes into a
perversion of a vastly simpler exercise that could be conducted easily
at the bench; and the reason for not going to the bench? Some infer
too hard (by lack of effort); others explicitly state it doesn't
matter (through reams of virtual pages gusting on about its
inconsequence); and yet others deferring it with excuses it demands
too much time for the effort.

Richard,

A simulation of a circuit is better than the "bench". I have components with
0% tolerance, 0 length leads, no parasitic components, and no power limits.
It does precisely what a physical meter is a compromise of.

It does not care whether there is a piece of coax connected to the circuit
or not. Neither does the physical meter. Both find SWR by calculating the
deviation of the load impedance from 50 Ohms.

Tam/WB2TT

On Tue, 14 Oct 2003 20:32:33 -0400, "Tarmo Tammaru"
wrote:

Richard,

A simulation of a circuit is better than the "bench". I have components with
0% tolerance, 0 length leads, no parasitic components, and no power limits.
It does precisely what a physical meter is a compromise of.

It does not care whether there is a piece of coax connected to the circuit
or not. Neither does the physical meter. Both find SWR by calculating the
deviation of the load impedance from 50 Ohms.

Tam/WB2TT


Hi Tam,

Simulations conform to nature, they do not enforce their own rules and
try to mimic someone's notion of "what should be."

If it does not care about coax, this kind of response is an implicit
statement of its being "too hard to manage" so-forget-about-it
approach to changing the problem to suit the answer. In other words,
a model of what? Nothing closer to the original than the oft-quoted
humor of "What is the definition of an elephant? A mouse built to
government specification!"

And so I return to the statement I objected to:
source impedance does not affect SWR.
which is shown no where to have been attempted, and is shown nowhere
to have been proven. What SWR? Where?

I note the total absence of technical answers to these specific
questions with proofs of unrelated doodling offered instead.

The condescension of
A simulation of a circuit is better than the "bench".
is absurd, especially when that same simulation fails to confirm bench
experience. I would challenge you to offer the testimony of any
single (credible) author of a simulator to stand by this profundity.

I note this last effort of yours is one of several iterations - which
simulation was the most perfect? The first or the last? Who is to
know? How is it to be known? Simulation did not describe to you what
you had to change in the simulation to achieve Nirvana. None of your
rationale for change emanated from the data, it sprang from the
experience of someone's bench providing superior results. If this
exercise is so much better, it should have taken only one pass to
accomplish. The negation of that is found in the failed attempts.
Thus the assertion of:
A simulation of a circuit is better than the "bench".
has been shown to be absurd through successive failures by the author
of that statement.

As I have offered before, there is humor to be found in the disconnect
and this *******ization by Cecil reigns supreme in examples. But to
its credit, it keeps me amused and offers considerable fodder for the
mythical lurker to observe where the logical landmines are (or in
counting the field's litter of amputees attempting pirouettes). ;-)

73's
Richard Clark, KB7QHC

Tarmo Tammaru wrote:
"Richard Clark" wrote in message
...

The mythical lurkers should note all the effort that goes into a
perversion of a vastly simpler exercise that could be conducted easily
at the bench; and the reason for not going to the bench? Some infer
too hard (by lack of effort); others explicitly state it doesn't
matter (through reams of virtual pages gusting on about its
inconsequence); and yet others deferring it with excuses it demands
too much time for the effort.


Richard,

A simulation of a circuit is better than the "bench". I have components with
0% tolerance, 0 length leads, no parasitic components, and no power limits.
It does precisely what a physical meter is a compromise of.

It does not care whether there is a piece of coax connected to the circuit
or not. Neither does the physical meter. Both find SWR by calculating the
deviation of the load impedance from 50 Ohms.

Tam/WB2TT

And, consequently, the results you get should be exactly the same as
those of us using equations rather than modeling simulations get. I
don't see any reason why people who don't believe the equations would
believe simulation results.

Roy Lewallen, W7EL

It does not care whether there is a piece of coax connected to the circuit
or not. Neither does the physical meter. Both find SWR by calculating the
deviation of the load impedance from 50 Ohms.

Tam/WB2TT

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

Your attitude is quite correct Tam.

But the situation is even worse than that! The so-called SWR meter cannot
even tell you the all-important sign of the deviation - just that a
deviation in some unknown direction exists.

The indicated SWR is meaningless. It is *supposed* (?) by the meter to exist
on a transmission line which does NOT exist. What does anybody ever do with
the imaginary value except argue about it on these walls and over the
air-waves.

The thing has been fooling gullible radio amaters and professionals ever
since it was invented. Sounds very technical and knowledgable though. A
good selling point. But it hardly engenders the amateur's "Self training
and education in the art of communicating by radio". It is positively
harmful.

In what year was it first introduced? I imagine it arrived very soon after
the first expensive 5 watt RF transistor came off the production line.

However, the 0-to-infinity SWR scale can easily be treated as a typing error
by dabbing on some of that white stuff.
----
Reg, G4FGQ

Richard Clark wrote:
A transmitter is loaded with two components and a meter placed between
them - woohah!

Richard, I've got Chipman's book now. Where does he say that SWR
depends upon the source impedance. He does describe a localized
resonance effect within a transmission line. Are you saying the
source impedance is a causal parameter for that localized resonance
effect?

Not arguing with you - just still trying to understand what you
are saying.
--
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:
As I have offered before, there is humor to be found in the disconnect
and this *******ization by Cecil reigns supreme in examples.

Hmmmmm, that "*******ization by Cecil" supports your side of the
argument, Richard. Would you rather it not support your argument?
--
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! =-----