Topband: Covered /bare antennn wire

[Eddy Swynar]

On 2012-11-15, at 3:42 PM, Bruce wrote:

> Dry blowing snow or high wind can cause quite some voltage build up on a antenna, especially a long one. It is possible to draw quite an arc to ground. 
> There have been reports of high voltage electrocutions from antenna static build up in Short Wave Broadcast stations. A short stick was mandatory for maintenance periods. 
> And yes, I did work at a shortwave station with 500 KW transmitter output.
> 
> So receiving antenna wire insulation could have some benefit if the voltage on a bare wire is leaking to a tree limb or across an insulator. Beyond some point all insulators can fail.
> 
> Indoor antennas do hear static, but I have never seen any evidence of voltage build up. ( The building may provide adequate insulation.)  
> 
> 
> Out of curiosity, has anyone ever really done testing of voltage buildup on a insulated antenna wire, VS a non-insulated wire ? 
> Indoor antennas VS outdoor antennas of equal size?
> 


Hi Bruce,

I am not so sure that the notion of insulated vs. uninsulated wire holds true in long wire spans...

Case in point: years ago when I first erected my 1500' long Beverage antenna here, I was specific in using insulated wire though its entire course because it runs through a grove of trees at one point. Well, one day, in the advance of an approaching storm front, I decided to ground the end of the Beverage in my shack. I could feel a "tingling" sensation as I man-handled the wire, negotiating my way to the common ground pipe that I have running the length of the back of my operating table...imagine my complete & utter shock as I neared the wire to this same pipe, and managed to induce 1/8" long blue arcs from the pipe to the wire!

Since that time---FWIW---I have always had a rugged 2.5 mh. RF choke clipped between the wire's end where it attaches to the matching transformer, and ground. In theory this acts as a static drain, I guess, but does not induce signals to ground. I've heard that a multi-megohm resistor will do the same thing at this point...

~73~ de Eddy VE3CUI - VE3XZ