When I was KA1DQG and in an apartment in Bridgeport, CT & not allowed to have antennas... I had two Hustler mobile sections I used opposed, as a short dipole on 80M that was on the carpet floor. Rig was a Kenwood 820S & the amp was a SB-221.
I am here to say I smelled the smoke before I saw the two large burnt areas at each of the ball ends where the corona ripped the carpet a pair of new ones. Luckily there was some unused carpet in the basement & I did the equivalent of a hair plug transfer and all was well. Corona at the ball end? Oh ya... 73, Gary KA1J > On 4/16/2019 5:38 AM, Jim Miller wrote: > > > Is there some zener like ionization at the top that limits the > > voltage? > > > > > jim ab3cv > > Supposedly, if you run a kW to a mobile whip on 80 meters, and the > whip has only a 1/4 inch metal ball on the top, you can get corona > discharge, like a Tesla coil. I have seen this problem fixed by > adding a copper toilet float ball atop the whip. Air has a known > electric field for breakdown, but it is a complicated problem to > calculate voltage by integrating the electric field from the tip of > the vertical to "infinity". If interested in the details, see > articles on Telsa coils. > > A quarter wave vertical would have MUCH less voltage on top, > of course. If it's still too high, it is easily reduced by > adding a top hat. > > I have a relay at the top of my 80 meter vertical. As > described in my QST article, I increased the spacing of > the contacts to 1/2 inch. I have never had any trouble > with this arrangement even at 1500W. Nor have any readers > of the article reported to me that their relays arc'ed over. > > It is far easier to simply overkill the voltage problem > rather than attempt to determine exactly how much voltage > is generated. > > Rick N6RK > _________________ > Searchable Archives: http://www.contesting.com/_topband - Topband > Reflector > _________________ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
