One very common error in putting antennas that rotate in/on a tower is
failure to bond the rotating mast to the tower. A flexible strap connected
to the mast with a couple of hose clamps and then to the top of the tower
via the same method will provide a path from the mast to the tower other
than through the rotor. Saves rotors and control boxes.
Also, put an "air terminal" on the top of the mast. A pipe cap with a 6" x
3/8" threaded rod attached, sharpen the end to a point and it will work very
nice.
73
Bob, K4TAX
----- Original Message -----
From: "Bill Fuqua" <wlfuqu00@uky.edu>
To: <tentec@contesting.com>
Sent: Wednesday, August 13, 2003 9:25 AM
Subject: Re: [TenTec] Another grounding thought and personal observation
> A little more about snake oil. About the only thing you can do to
> control where lightning is going to strike is to attract it, more or
> less. A lightning rod or one of these dissipation brushes produce a
corona
> which produces a great deal of ozone and free electrons. If the path of
the
> lightning come near enough to this cloud of charges it may take that path
> back to the lightning rod or brush and then to "ground". One thing you
> can do on a tower is to have a lightning rod with its own very heavy
> ground conductor to perhaps encourage the lightning to hit it rather than
> your antennas. The induced currents and paths for currents are another
matter.
> I had a direct hit on a TA33 once. It did not hurt anything in
the
> house but it did interesting damage to the antenna.
> About on inch away from the end of the reflector there was a 1/4 inch
> hole in the aluminum tube. The hole was almost circular and there was a
> large "frozen" drop of aluminum hanging down inside of tube from the edge
> of the hole. The plastic cap on the end of the element was not melted or
> effected in any way. This seemed very strange but that was how I found it.
> The traps survived by the way.
> 73
> Bill wa4lav
>
>
>
> >Talk about "snake oil" this dissipation brush thing is nuts. A bunch of
> >sharp wires on the top of an tower is supposed to prevent lightning? If
> >there is a high potential between these wires and the clouds it will
cause
> >field ionization of the atoms and molecules at the sharp tips of the
wire.
> >This will not dissipate the charge ( lots of coulombs stored between
earth
> >and clouds) at all unless
> >there is a tremendous discharge ( lightning).
> > Where the lightning goes depends where the random paths of the
> > cosmic rays that strike the atmosphere. The cosmic rays ( very high
> > energy particles) leave ionization trails that cross each other and when
> > these paths happen to make a connection between the clouds and earth
> > there is a discharge. That is why lightning seems to be a bunch of
> > connected straight lines.
> > The guys that sell the dissipation brushes put these on top of a
> > little Van de Graaff generators and then show that they get a much
> > smaller arc off the dome than without the "brush". However, the charge
on
> > the dome of the Van de Graaff is very small and the rate at which it can
> > be charged (current) is limited by the amount of charge the little
rubber
> > belt can carry from the grounded base to the dome. The field ionization
> > at the tips of the wires produces a corona that discharges the dome of
> > the Van de Graaff and in effect reduces its voltage. We use corona
> > loading to regulate the dome (high voltage terminal) voltage on our
large
> > Van de Graaff accelerator. And when it discharges at 5 or 6 MV it makes
> > quite a noise. Lightning involves many more coulombs of charge than the
> > salesman would have you think.
> >
> >
> >73
> >Bill wa4lav
> >
> >_______________________________________________
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> >TenTec@contesting.com
> >http://lists.contesting.com/mailman/listinfo/tentec
>
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