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Old December 24th 07, 03:09 PM posted to rec.radio.amateur.antenna
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First recorded activity by RadioBanter: Mar 2007
Posts: 3,521
Default Standing-Wave Current vs Traveling-Wave Current

Denny wrote:
1. A standing wave is not 'standing' in time... It phase rotates at
the same rate as the excitation frequency...


Yes, but that rotation is occurring at a fixed point on
the wire. The standing wave is not moving - it is just
rotating in a fixed place on the wire. Standing waves
do not flow. They are basically an illusion created by
the superposition of two traveling waves.

2. It is real because I can measure it with a volt meter and I can
extract power from it with a lamp, simultaneously..


You cannot extract steady-state power from standing waves.
You can only extract steady-state power from traveling waves.

However, you can extract transient-state power from standing
waves. That's what happens at key-up - the energy in the
standing wave is radiated after the source is disconnected.

Try this thought... A Tesla coil (automobile spark coil) with no load
on the output is all standing wave voltage and no current - so
according to some has no power... Touch your finger to it...


When you touch your finger to it, it is no longer steady-state.
Standing waves can and do give up their energy as joules/sec
power during transient states. But they change during that
process.
--
73, Cecil http://www.w5dxp.com
 
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