Dave wrote:

"Henry Kolesnik" wrote in message
...

I know that a shorted 1/4 wave stub exhibits a very high impedance. But
for the 2nd harmonic it's a 1/2 wave stub and exhibits a very low

impedance

or a short. There are claims that this can be used to filter the even
harmonics. Shorts can't diisipate power and must reflect, so how does a
stub work?


stubs work very nicely. you can get practical stub information at my web
site, including how to build a 40m to 15m 3rd harmonic stub filter:
http://www.k1ttt.net/technote/techref.html#filters

as you may have noticed by now you have kicked the proverbial hornets nest.
reflections are a touchy word in this group, usually attracting the endless
argument that travels from thread to thread. in time this will deteriorate
into name calling and endless argument over reflections, interference,
virtual impedances, and a few other topics.




We bounce between the Physics of Operation and the Practicalities of
Engineering. We have experts on all sides of the issue grin. And,
typically, engineers and physicists both use English but can't
communicate well grin, again grin

But your basic question is how does one answer your question: "Shorts
can't dissipate power and must reflect, so how does a stub work?"

In practical terms, you have answered your own question! Reflections.

In Physics terms, you have to deal with the wave inside the stub and the
[V^2(theta) + I^2(theta)] energy storage as a function of position
within the stub and the corresponding sources of loss also a function of
V^2 and I^2 inside the stub and finally the reflections that exist
within the stub caused by the intentional physical short circuit [or
open circuit].

So, are you pursuing Physics or Applications type knowledge?