[TowerTalk] Polarity question..on a dipole

[Steve, W3AHL]

A similar question was posed a few months ago and I compared the actual measured voltage on the end of a dipole to that “measured” by EZNEC using a zero amp Source placed very near the end segment of an element and found good agreement between the two.

So based upon that, at resonance with an SWR of 1:1 a 75M dipole fed with 1500 watts has about 3400 v RMS “near” the tip of the wire.  The two wires’ current and voltage are 180 degrees out of phase, so the voltage between the tips would be the peak to peak value of 9600 Vpp, assuming a sinusoidal waveform.  Operating off resonance and with an SWR > 1:1 will change the voltage, so a safety factor should be added (or the actual condition modeled).

My experience with the typical black Dacron rope as an insulator has been – it isn’t, when dirty and wet.

Steve, W3AHL
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Date: Fri, 31 Mar 2017 12:25:46 -0700
From: "Jim Thomson" <jim.thom at telus.net>
To: <towertalk at contesting.com>
Subject: [TowerTalk] Polarity question..on a dipole

Ok, the peak V on the tips of a dipole is sky high.   But what about the polarity between
the ends ?    If one end is + 10 kv, is the other end at ? 10 kv  ??   Is there  a 20 kv
potential difference between them at all times ? 

Jim  VE7RF