Maybe I have a misunderstanding. I see a "mismatch" as being caused by only
two factors, either an uncompensated reactance--or, as Cecil mentioned,
feeding a bal/unbal antenna with the wrong feedline.
Indeed, any feedline can simply be analyzed as a series of lumped
reactances--inductive and capactitive.
How should I be viewing this?

Regards,
John

wrote in message
oups.com...
How does a mismatch affect the radiation pattern?
tnx .....

It doesn't. I don't consider unbalanced, the same as mismatched,
to answer Cecils question. Feedline radiation can effect the
pattern due to a lack of balun, etc, but thats not the same thing as an
impedance mismatch. Also...Antenna "loading" is not the same as
antenna "matching". Many short verticals need both...
MK

Errr, let me be a bit more specific...

The "beam width" of a quarter-wave has a very wide "acceptance ratio" and
grabs much more reflection from the ionosphere--a half-wave has a much
narrower beam width--it is a "quieter" antenna, but, grabs more of the
signal I am after...

At least, it appears like that...

A five-eights-wave has even a lower beam width--these three antennas,
because of length differences, exhibit differing reactances, when these
reactances are cancelled (such as using an L-Match) they become
"matched"--right?

Of course, this ignores conductor resistance, and takes for granted the
antenna is being fed at the proper point...



Regards,

John


"John Smith" wrote in message
...
Maybe I have a misunderstanding. I see a "mismatch" as being caused by
only two factors, either an uncompensated reactance--or, as Cecil
mentioned, feeding a bal/unbal antenna with the wrong feedline.
Indeed, any feedline can simply be analyzed as a series of lumped
reactances--inductive and capactitive.
How should I be viewing this?

Regards,
John

wrote in message
oups.com...
How does a mismatch affect the radiation pattern?
tnx .....

It doesn't. I don't consider unbalanced, the same as mismatched,
to answer Cecils question. Feedline radiation can effect the
pattern due to a lack of balun, etc, but thats not the same thing as an
impedance mismatch. Also...Antenna "loading" is not the same as
antenna "matching". Many short verticals need both...
MK

"John Smith" wrote
The "beam width" of a quarter-wave has a very wide "acceptance ratio" and
grabs much more reflection from the ionosphere--a half-wave has a much
narrower beam width--it is a "quieter" antenna, but, grabs more of the
signal I am after...
_____________

A 1/2-wave VHF/UHF vertical has more gain at lower elevation angles than a
1/4-wave, but that may not usefully improve the SNR of the system. Most of
the noise power in these antennas doesn't arrive from higher angles anyway,
because those freqs don't reflect well from the ionosphere.

RF

No. Feeder radiation has *nothing* to do with impedance
matching. Zero. Nada...Zilch. Ever!...You can have a perfect
1:1 match, and still have feedline radiation. Or you can have
a horrible impedance mismatch, and have very little feeder
radiation. Feeder unbalance, lack of baluns, chokes, etc, etc,
should never be confused with impedance matching. I don't
think the term "mismatch" should be applied to a lack of balance,
etc...If you tell me you have a mismatch, I'll always assume you
mean impedance. Anyway, no matter my views...
Impedance mismatch will never change the pattern of the antenna.
For practical purposes, it's the same as raising or lowering power
to the antenna. If you run 50 more watts to an antenna, it's pattern
does not change. Ditto, if you run 50 less...MK

huh? If you have an impedance mismatch, you are NOT feeding the antenna at
the proper point, or with the proper ohm line, or without a proper matching
circuit! Either one of these will exhibit some type of reactance!
OR! OMG! My "knowledge"/thinking is in error!
????

Regards,
John
wrote in message
ups.com...
No. Feeder radiation has *nothing* to do with impedance
matching. Zero. Nada...Zilch. Ever!...You can have a perfect
1:1 match, and still have feedline radiation. Or you can have
a horrible impedance mismatch, and have very little feeder
radiation. Feeder unbalance, lack of baluns, chokes, etc, etc,
should never be confused with impedance matching. I don't
think the term "mismatch" should be applied to a lack of balance,
etc...If you tell me you have a mismatch, I'll always assume you
mean impedance. Anyway, no matter my views...
Impedance mismatch will never change the pattern of the antenna.
For practical purposes, it's the same as raising or lowering power
to the antenna. If you run 50 more watts to an antenna, it's pattern
does not change. Ditto, if you run 50 less...MK

wrote:
No. Feeder radiation has *nothing* to do with impedance
matching.

Note Webster's has a different definition of mismatch
than the IEEE Dictionary. That's why I asked for a
definition. For instance, going from a black coax to
an orange coax could be called a color "mismatch".
--
73, Cecil http://www.qsl.net/w5dxp

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A two conductor transmission line, with Earth or other conductors
providing a potential third conductor, has two defined impedances. One
convenient and intuitive way of defining these two is as common-mode and
differential-mode (or even and odd mode) impedances. Our measurement
equipment invariably measures the differential (odd) mode impedance, so
when we speak of impedance "matching" or "mismatch" we virtually always
mean matching of differential mode impedance.

Differential mode currents don't contribute to radiation. Differential
mode impedance match or mismatch has no effect at all on antenna
pattern. It can have an indirect effect on antenna *system* performance
due to potential losses in impedance matching components. But otherwise
the quality of impedance match can be ignored when considering antenna
performance.

Common mode current radiates, so a transmission line carrying common
mode current (a twinlead line with imbalanced currents, or a coax line
with current on the outside of the shield) is actually part of the
antenna. Anything which alters the current flow or distribution of this
current (for example, a current balun) will alter the overall radiation
pattern. If a transmission line is perfectly balanced, the common mode
current is zero, and the term "match" or "mismatch" can't be
meaningfully applied to the common mode impedance.

Roy Lewallen, W7EL

Cecil Moore wrote:
wrote:

No. Feeder radiation has *nothing* to do with impedance
matching.


Note Webster's has a different definition of mismatch
than the IEEE Dictionary. That's why I asked for a
definition. For instance, going from a black coax to
an orange coax could be called a color "mismatch".