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
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