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 _______________________________________________ Topband reflector - topband@contesting.com