A few of the really big multi's also have 4 square arrays for 20-15-10 in
addition to
their large stacked arrays. I'm sure these are a big help during high rain
static
episodes.
73,
Larry K4AB
On Wed, Apr 22, 2015 at 10:04 AM, john@kk9a.com <john@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@contesting.com
> Subject: Re: [TowerTalk] Precipitation static
> From: David Robbins <k1ttt@verizon.net>
> Reply-to: k1ttt@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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