Topband: Covered /bare antennn wire

Tom W8JI w8ji at w8ji.com
Thu Nov 15 15:25:23 EST 2012


> 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 
trees.

73 Tom 



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