Steve Nosko wrote:
Oops! Time to wipe the CRT clean... Henry wants to discuss a SHORTED
stub...reset. end. stop.

Sorry, a shorted 1/2WL stub exhibits a short at the fundamental frequency
and an open when it is 1/4WL at 1/2 the frequency of the first. Same
principles apply.

Absolutely nothing except superposition and interference happens at the
mouth of a stub. All the reflected action happens at the physical open
circuit. Virtual impedances are only a V/I ratio and CANNOT cause
reflections. Absolutely no reflections are happening at the mouth of
the stub (unless a physical impedance discontinuity exists there).

\\ Nit alarm on\\ (Though I consider this a clarification in an attempt
to simplify the explanation and remove the extra complexity added by the
double terms) I consider superposition and interference to be the same
thing.

So do I. I probably should have said superposition/interference, which logically
equals (superposition AND interference) since ONE AND ONE = ONE.

Consider this. If a stub really presented an infinite impedance, you could
simply remove it and nothing would change.

At the fundamental (_OPEN_ 1/4W stub, remember) this IS TRUE.
Are you saying that the 1/4W _shorted_ stub addition or removal makes a
BIG difference at the fundamental -I think not, or you still talking about
the 1/4W _open_ stub which kills the system at the fundamental when added.

Any stub that presents an infinite impedance should be able to be removed
and without anything changing. You have an infinite impedance before the removal
and you have an infinite impedance after the removal, so nothing changes when
you remove the stub. (Hint: Devil's advocate reasoning applied) Of course,
something changes when one removes the stub - that's the entire point. There
are forward components and reflected components flowing in and out of a stub.
That's why removing it changes things.
--
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! =-----

"Cecil Moore" wrote in message
...
Steve Nosko wrote:
Oops! Time to wipe the CRT clean... Henry wants to discuss a SHORTED
stub...reset. end. stop.

Sorry, a shorted 1/2WL stub ... Same
principles apply.

That's why I went ahead and continued on the "complementary situation"
[...]

Any stub that presents an infinite impedance should be able to be removed
and without anything changing. You have an infinite impedance before the
removal
and you have an infinite impedance after the removal, so nothing changes
when
you remove the stub. (Hint: Devil's advocate reasoning applied)

Your "Devil's advocate "meaning escapes me...


Of course,
something changes when one removes the stub - that's the entire point.
There
are forward components and reflected components flowing in and out of a
stub.
That's why removing it changes things.

Yea, but in the practical sense, it does not change anything at the
fundamental (desired) frequency [[high Z stub, power still to the load]].
It's only when you consider the harmonics, if they are there, that anything
important changes, right. So I'm puzzled why you included that part in your
comment.
--
Steve N, K,9;d, c. i My email has no u's.

Steve Nosko wrote:
Yea, but in the practical sense, it does not change anything at the
fundamental (desired) frequency [[high Z stub, power still to the load]].
It's only when you consider the harmonics, if they are there, that anything
important changes, right. So I'm puzzled why you included that part in your
comment.

Some people believe that there is no current flowing into or out of a
1/4WL shorted stub. But all they have to do to change their minds is
measure the current through the short at the end of the stub. It is sky
high. The SWR inside a 1/4WL shorted stub is near infinite, i.e. the
square root of Pr/Pf inside a stub is near unity.
--
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! =-----

Any stub that presents an infinite impedance should be able to be removed
and without anything changing. You have an infinite impedance before the
removal and you have an infinite impedance after the removal, so nothing
changes. There are forward components and reflected components flowing in and
out of a stub. That's why removing it changes things.

Is it because energy is stored in the stub? If the impedance is infinite then
no power dissipation is removed from the system. Something is dynamic in
nature in this example because if you remove an infinite impedance, nothing
will happen. Could the change be due to the fact that the stub is in the near
field of the antenna and subject to induced rf currents? If this were the
case, then removal of the stub would change things.
If the stub presents an infinite impedance, with no external influences,
removing it should have no effect. If the stub were replaced with a quality
parallel resonant LC circuit in a shielded box, would removing it make any
difference? I don't know, I am asking.


73 Gary N4AST

JGBOYLES wrote:
If the stub presents an infinite impedance, with no external influences,
removing it should have no effect.

Exactly! Therefore, the infinite impedance at the mouth of a stub
is a virtual impedance, not a physical impedance. The physical
impedance exists at the end of the stub where all the reflections
are taking place. Reflections occur only at a physical impedance
discontinuity.
--
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! =-----