[TowerTalk] Polarity question..on a dipole

[Doug Smith]

Voltage at dipole tips — it’s a kind of interesting question.  

I was thinking of putting a dipole in a stand of aspen trees which I do NOT want to burn down.  There is no way to route the wires to completely avoid contact with the twig-like upper branches.  And, I do run full power.

I did find some high voltage wire by Gore that is rated at 13 KV although I’m not sure that was at RF — might have been DC.  It is insulated with PTFE.  Looked interesting..

The idea of looking at the feed point impedance of a 1 wavelength doublet for a first order approximation is a good one.  I may try modeling that, just to bring closure to my idea..

73,
Doug, W7KF



> On Mar 31, 2017, at 2:39 PM, jimlux <jimlux at earthlink.net> wrote:
> 
> On 3/31/17 12:25 PM, Jim Thomson wrote:
>> 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 ?
>> 
> 
> It's very hard to calculate (or measure) the actual voltage at the ends - best you can say is "it's high".  You can infer a voltage by calculating the feedpoint impedance of a 1 wavelength long doublet, then putting in 2x power (each half radiates full power), and using Ohms law.
> 
> 
> Yes, it would be opposite polarity.  but not "at all times" because it goes through zero every half cycle.