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[TowerTalk] Pl-259 Flash over voltage

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Subject: [TowerTalk] Pl-259 Flash over voltage
From: "K8RI on TowerTalk" <>
Date: Fri, 1 Dec 2006 19:19:56 -0500
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The talk about breakdown voltage which is basically air across the space 
between the inner and outer conductors at the PL-259. Given LMR-400 has 
roughly 34 pfd per foot (23.9) or 230 pfd per hundred feet that is not a lot 
of capacity.

The arc is initiated when the breakdown voltage across the gap is reached, 
but when the arc is a bright blue and extends out from the end of the 
connector by a 1/4 inch or more it has to consist of much more than a 
microamp. I'd guess the brightness, thickness, and amount the arc extends 
out from the tip are determined by the magnetic field induced due to rise 
time and current.

So I wonder just how much current could be in some of these arcs.  I 
wouldn't think it'd be much due to the small capacitance, but the size of 
the arc, the brightness, the sound volume, and the poke they sometimes give 
indicates a substantial charge.  Where would that come from?  Remember we 
are not talking about induced voltages due to nearby lightning strikes.

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2 


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