Topband: Covered /bare antennn wire
jlangdon at outer.net
Fri Nov 16 09:10:23 EST 2012
It also doesn't seem to matter if the antennas in the stack have their
elements insulated from the boom or bonded to it, the top antenna always has
+20 dB or more noise.
73 John N5CQ
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Tom W8JI
Sent: Thursday, November 15, 2012 2:25 PM
To: Bruce; topband at contesting.com
Subject: Re: Topband: Covered /bare antennn wire
> As you have said it is difficult to get a A-B test unless instant
> switching or direct observation is available.
The purpose of my test was to see if p-static was caused by individual
charged particles as they hit the wire, or some other mechanism like corona
discharge into the charged air or charged cloud of particles.
My thought was if it was charged particles each making noise, the pitch or
frequency distribution would be at the rate of particle contact, and that
insulation should mute the effect by slowing rise time of charge transfer
from particles to the wire.
Clearly the noise was all from corona at sharp points.
This also agrees with the effects people with multiple antennas see, or even
two-way antenna on tall buildings or towers. The highest and most protruding
antenna has the first and worse noise. Grounded elements, fiberglass
housings, and other tricks make no difference at all. The only thing that
matters is streamers from the exact point of corona leakage.
We saw this when a repeater moved from side mount on a tower to a building
roof peak. The fiberglass Station Master was swapped for a grounded folded
dipole antenna, and both were equally useless in bad weather. The only thing
that improved p-static noise was using an antenna well below the height of
other sticks on the roof, but that didn't work out because of severe pattern
nulls. We could raise the antenna and watch the noise increase, and at the
same time actually hear the same sizzling acoustically through our ears and
see it at night from antenna tips.
Everyone with stacked monoband identical Yagis sees this on the top antenna.
The top antenna is always terrible in inclement weather, even though the
same precipitation strikes all antennas equally and the antennas are all on
the same tower.
This all, since it all always agrees, clearly means the noise has nothing to
do with static drain or insulated or bare conductors. It is all about where
the highest voltage gradient to space around the antenna is, and how easy
that point can "leak" (generate corona).
> I was hoping for a test something like, side by side identical wires,
> one insulated, and one un-insulated with voltage measuring devices at
> the ends.
> Also separated enough not to get Beverage coupling, and using real
> stormy weather measuring.
> Over the insulation breakdown voltage, one would expect them to be
> equal anyway.
Leakage current to earth was identical in my spray tests. It has nothing to
do with insulation breakdown. It is more like the effect of a charged
plastic comb. The charge obviously distributed right through the insulation.
I suppose if the insulation was really thick the charge migration would be
pretty slow, but charging of the wire is not what makes the noise we are
concerned with. The noise comes from corona.
I've had insulated wire Beverages and bare wire Beverages since the 1960's
or 1970's, often at the same time as mixtures of wire. Neither is any
quieter for me for local storm static.
My bare wire Beverages here are dead quiet even while Yagi's are useless in
foul weather, unless the Beverage points at the towers or are near tall
Topband reflector - topband at contesting.com
More information about the Topband