[TowerTalk] Precipitation static

[Scott Johns]

At the WM5G station Jim and his ops were known to praise his quad when the
yagis/stacks were plaqued by rain static.


On 4/22/15 11:04 AM, "john at kk9a.com" <john at kk9a.com> wrote:

>Rain static can be a real pain during a contest.  Using only lower
>antennas helps but in my station the static on these can still be pretty
>strong.  Perhaps my lowest antennas are not low enough.  What do the big
>contest stations use during rain static conditions?  Is a SteppIR really
>quieter?
>
>John KK9A
>
>
>To:	towertalk at contesting.com
>Subject:	Re: [TowerTalk] Precipitation static
>From:	David Robbins <k1ttt at verizon.net>
>Reply-to:	k1ttt at arrl.net
>Date:	Wed, 22 Apr 2015 06:54:10 -0500 (CDT)
>
>precipitation static really doesn't require any precipitation or
>lightning, it
>is due to corona created by the high electric field under a convective
>cloud.
>If the field gets high enough then lightning is likely to accompany it...
>when
>lightning strikes from such a storm it momentarily lowers the electric
>field
>gradient which reduces or stops the static until the field builds again.
>because the gradient is between the ground and cloud the higher the
>antenna the
>worse the corona.  and having other antennas above reduces the gradient on
>the
>lower ones so lower antennas in a stack are often quiet when the top one
>is
>noisy.
>
>all grounded construction doesn't help because the charge causing the
>corona is
>not building up on the antenna because of triboelectric charging like you
>can
>get with windblown snow or sand.  in those cases the charge is put on the
>antenna by contact with the snow or sand and can be drained by a resistor
>or
>inductor.  in the case of corona from the electric field it is actually
>the
>cloud attracting the charge up the structure from the ground causing a
>concentration near the tips of the elements.  Since the charge is drawn up
>from
>the ground any other connection to ground through a resistor or inductor
>won't
>drain it off.
>
>Most likely the steppir is quiet because it is essentially wrapped in
>fiberglass which may help prevent corona by shielding the conductive
>parts of
>the elements or just reducing the field gradient near the tips of the
>elements...  note that Telrex used to try to do that by adding balls to
>the
>tips of their elements on some models... that didn't seem to help on the
>ones I
>had, I suspect because they still had lots of sharp points due to the
>screws
>through the elements and corners on T-match shorting plates.
>
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