Thread: Standing waves
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Old September 22nd 09, 01:13 PM posted to rec.radio.amateur.antenna
Cecil Moore[_2_] Cecil Moore[_2_] is offline
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First recorded activity by RadioBanter: Mar 2007
Posts: 3,521
Default Standing waves

Szczepan Białek wrote:
Now we should work out
the consensus on which part of the radiator radiate the radio waves.


Here's what you are missing: RF is AC. At some point
in the radiation cycle, the instantaneous radiation has
to be zero at the zero-crossing time. That is when the
magnetic field energy is essentially zero and close to
100% of the energy is contained in the electric fields
at the ends of the dipole.

You cannot have it both ways. You cannot have a radiation
peak at a net current maximum time and also have a radiation
peak at a net voltage maximum time since they are ~90 degrees
out of phase. If what you are saying were really happening,
an antenna would radiate two times the applied frequency,
but it obviously doesn't.

Or did you not realize that when the electric field is
at its maximum amplitude, the current is close to zero-
crossing all up and down the standing wave antenna? The
phase of the feedpoint current is within a couple of
degrees of the phase of the current all up and down
the antenna.

That's why the current on a standing wave antenna cannot
be used to measure the delay through a wire or a loading
coil. All such "measurements" are bogus.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com