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
...

"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.

Dave wrote:
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

A fellow ham sent me an email suggesting a use for a shorted
1/4WL stub that had not occurred to me before. Many hams have
static electricity problems with dipoles since there is not
a DC path between the poles. For a single-frequency dipole,
a shorted 1/4WL stub could be installed at the feedpoint to
drain off the static electricity without affecting the
performance much on the fundamental frequency. It would also
aid in the suppression of even harmonics.
--
73, Cecil http://www.qsl.net/w5dxp



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Henry Kolesnik wrote:

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...

They indeed do attenuate or reject. Reflections is the method by which
stubs accomplish the attenuation or rejection. If one is only interested
in implementing stubs, and not interested in how they work, one need not
deal with reflections. What one must realize, however, that the SWR inside
a resonant stub is as high as it can be. All the reflections take place at
the shorted or open end of a stub, i.e. at the physical discontinuity point
where rho = |1.0|.

I don't have any argument with people who say, "I only want to use stubs.
I don't care how or why they work." My argument is with people who falsely
describe how they work, e.g. "Since the impedance looking into a shorted
1/4WL lossless stub is infinite, no current flows into or out of the stub."
If that were really true, one could remove the stub without changing
anything. The net superposed current may be zero but the forward and reflected
currents exist there and can be very high values. In fact, I have melted the
insulating material at the end of a shorted coaxial stub due to high I^2*R losses.
--
73, Cecil http://www.qsl.net/w5dxp



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yes, that works very nicely also. it does provide a dc ground for otherwise
ungrounded antennas like verticals or dipoles providing a way for static
build up to drain safely.

"Cecil Moore" wrote in message
...
Dave wrote:
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

A fellow ham sent me an email suggesting a use for a shorted
1/4WL stub that had not occurred to me before. Many hams have
static electricity problems with dipoles since there is not
a DC path between the poles. For a single-frequency dipole,
a shorted 1/4WL stub could be installed at the feedpoint to
drain off the static electricity without affecting the
performance much on the fundamental frequency. It would also
aid in the suppression of even harmonics.
--
73, Cecil http://www.qsl.net/w5dxp



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-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

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
m...
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
...

"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.

A fellow ham sent me an email suggesting a use for a shorted
1/4WL stub that had not occurred to me before. Many hams have
static electricity problems with dipoles since there is not
a DC path between the poles. For a single-frequency dipole,
a shorted 1/4WL stub could be installed at the feedpoint to
drain off the static electricity without affecting the
performance much on the fundamental frequency. It would also
aid in the suppression of even harmonics.
--
73, Cecil http://www.qsl.net/w5dxp



Very effective way for monoband antennas. The improved version of this is the
"Bazooka Balun" which besides above mentioned benefits acts as a balun. I used
it on all my monoband antennas. Provides DC path to ground, harmonic
supression, RF choke function and balanced to unbalanced feed point conversion.


Yuri, K3BU.us
www.computeradio.us home of Dream Radio One

Dave wrote:
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.

Where is the bulk of the attenuation taking place, at/in the stub,
or as a V^2/R loss back upstream? (Not a trick question)
--
73, Cecil http://www.qsl.net/w5dxp

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
m...
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
...

"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.

Yuri Blanarovich wrote:
Very effective way for monoband antennas. The improved version of this is the
"Bazooka Balun" which besides above mentioned benefits acts as a balun. I used
it on all my monoband antennas. Provides DC path to ground, harmonic
supression, RF choke function and balanced to unbalanced feed point conversion.

A 4:1 toroidal balun will also do the same thing -
provide a DC path between conductors.
--
73, Cecil http://www.qsl.net/w5dxp

you can look at it various ways.
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
m...
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
...

"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.