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
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