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Old April 5th 06, 05:30 AM posted to rec.radio.amateur.antenna
Cecil Moore
 
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Default Current across the antenna loading coil - from scratch

Roy Lewallen wrote:
And in any case, the statement about EZNEC is incorrect. As I explained
in a posting a short while ago, EZNEC has no awareness of nor does it
make any use of traveling wave currents or voltages. It calculates only
the total current from fundamental rules which don't involve traveling
waves.


For anyone who thinks EZNEC doesn't report traveling wave currents
differently from standing wave currents, please download the following
files.

http://www.qsl.net/w5dxp/testx.EZ

This is a *traveling wave file*. EZNEC reports the nearly linear phase
of the current from 0 degrees at the source to 90 degrees at the load.
The file comes with a zero load in the center of that 90 degree run.
EZNEC reports the current's phase at 45 degrees at that zero load.

http://www.qsl.net/w5dxp/testy.EZ

Removing the resistive load from testx.EZ turns it into a *standing
wave configuration*. EZNEC reports the phase of the current close
to zero degrees all up and down the wire. The file comes with a
zero load in the center of the same wire as above. EZNEC reports
the current's phase very near zero degrees. The phase is near zero
degrees all up and down wire 2.

Contrary to what you have been told, EZNEC clearly reports the
difference between the traveling wave configuration and the
standing wave configuration. The traveling wave current phase
can be used to measure the phase shift through the wire (or
through a coil). The standing wave current phase cannot.

To summarize: For the traveling wave configuration, the current
magnitude is essentially constant all up and down the line while
the phase shifts smoothly from zero degrees at the source to
90 degrees at the resistive load.

For the standing wave configuration, the current magnitude
follows the familiar cosine envelope from source at zero
degrees to the end of the antenna at 90 degrees. The phase
of the standing wave current is unchanging near zero degrees
all up and down the wire.
--
73, Cecil http://www.qsl.net/w5dxp
 
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