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[TowerTalk] Voltage vs Current feed

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Subject: [TowerTalk] Voltage vs Current feed
From: (Tom Rauch)
Date: Mon, 15 Oct 2001 20:17:41 -0400
> Am I correct?  Because of the open circuit (usually) at the far end of
> the antenna, the current must be zero throughout a cycle.  If this is
> true, it seems to make sense to begin analysis starting at the far end
> and work back to the source using the thoughts expressed in the above
> posting.  The feed then can be seen to be a function of antenna
> length.  Do standing waves alter this observation?

That's all right as far as I could see except current never really is 
absolutely zero at the ends because there is still coupling off the 
end into the electric energy storage field. You start at the open 
end, or farthest point, and work inwards. 

The voltage maxima (or loop or node) is at the open end, because 
there is "nothing much" for current to flow into. The current loop, 
node, or maxima is generally 1/4 wl in, but that assumes the wire 
is not loaded in any way, including having most or all of the electric 
field surrounding the conductor in a dielectric with a Vp of light 

Radiation comes from charge acceleration, and so the amount of 
EM radiation from any point relates to the ampere/feet of the 
system. That's why books tell us to keep the current loop (or node 
or maxima) as straight as possible, and why antennas like the 
CFA and EH antenna are only someone's wild dream.

The large close effects are induction fields related only to energy 
storage (magnetic from the movement of charges and electric 
because of the distribution of charges), but these fields decay 
much faster than the weaker radiation field which is what we use to 
Loop antennas and loaded antennas are the ones hardest or 
impossible to generalize.

That's about all we need to know in the world except lefty loosey 
righty tighty and poo don't run up hill.
73, Tom W8JI 

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