Dave wrote:
you can look at it various ways.

As I mentioned above; engineers, technicians, wave mechanics,
physicists, experimenters, etc., ALL live on this list grin. Mea
Culpa, I'm a retired engineer.

Just remember, stubs WORK very well. Thank the owner of your local
repeater for tuning the stubs [AKA CAVITIES] to reduce the desense below
receiver response levels, typically -120 dB or more attenuation.


1. the wave traveling wave analysis... the harmonic goes down the stub,
reflects back, and when it gets back to the transmission line it is 180
degress out of phase with the next cycle so it cancels it at the junction...
therefore there is no harmonic to propagate down the line past the junction.
this of course will raise the hackles of the anti-reflectionists who will
then say there is also no harmonic left to propagate down the stub which
means there is a virtual short at the junction, but no way to generate it
since nothing can be there to go down the stub.

2. the power analysis. power goes in, power comes out, it all reflects back
and forth until the energy becomes infinite and the amp blows up... but of
course energy is conserved and momentum must go somewhere so the stub
probably walks across the table with each wave reflection.

3. the sinusoidal steady state analysis. this takes the stub and transforms
the shorted impedance at the far end back to the junction and then does all
calculations as if the real short existed at the junction.... this will of
course annoy the reflectionists who will point out in never ending detail
how you can't explain tv ghosts, radar, or other transient phenomena this
way... of course by assuming the sinusoidal steady state at the start you
exclude those systems from this type of analysis, but that won't stop the
protests.

4. the s analysis... who know what this will say except cecil who will find
some way to steer the discussion over to it.

5. the optical layer analysis... see above.

"Henry Kolesnik" wrote in message
...

I know they work! One of my reasons for asking the question is I've not
found any mention in the literature of where the
"attenuation/rejection/reflection/filter residue" goes.

--
73
Hank WD5JFR
"Dave" wrote in message
...

the harmonic is 'attenuated' in that the magnitude of it is reduced when

the

stub is in line. i look at it like you could replace the stub with a

lumped

filter at the same point so the term attenuation makes more sense than
reflections or rejections... i don't really care where the harmonic

goes,

i

want to know how much it is attenuated by so i can compare with other

types

of filters.

"Henry Kolesnik" wrote in message
.com...

Dave

Nice site, I like the "white paper" approach as I prefer the info

without

the glitter. I've only read a few items and I
quote: "This is a plot of the attenuation provided by the stub. You

can

see

that it provides about 32db of attenuation at 28.25Mhz. " I've

noticed

that

the literature I've purused indicates that stubs either attenuate or

reject.

None say reflect! I don't want to get into a discussion of word

definitions

becasue reflect and feject are close but attenuate is not in the same

class.

Comments...

--
73
Hank WD5JFR

"Dave" wrote in message
news
"Henry Kolesnik" wrote in message
y.com...

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.