Deni F5VJC wrote:
I have recently been plagued by rain static on a new vertical antenna,
this a 42 foot vertical fed at the base through an SG230 auto tuner,
and used on all bands. It seems I need a static bleed of some sort, a
choke or resistor. What is the best component to use in an outdoor
environment?
Take a look at page 4 of the schematic. There is already
a static bleed through 20 turns on a transformer winding
to ground plus about 40K ohms of resistance to ground. You
are already bleeding the static charge, just not fast enough
to get rid of the RF content. The problem is that the
RF content of the precipitation static is finding its
way through your receiver along with the desirable RF
signals. Question is: Is there something that discriminates
against local RF static without discriminating against
desirable RF signals?
Here's my two cents and others certainly do vehemently
disagree with me.
A single precipitation static charge transfer is at a
localized point. Desirable arriving RF waves/photons are
spread out over the entire antenna. That should make them
separable.
Folding the antenna into a loop is one way to reduce
precipitation static. Desirable arriving RF waves are
unaffected by folding as they encounter the entire antenna,
i.e. it's hard to tell the difference between the
performance of a dipole and a folded dipole.
Single charges of precipitation static, however, are
confined to one point on the antenna. If there is a discharge
path to the other side besides through the receiver, the
charge will at least partially take the shortest path of
reduced resistance. IMO, that's why folded antennas are
quieter than open-ended antennas as far as precipitation
static is concerned.
The way I reduced the problem with open-ended antennas is
to use heavily insulated wire. Bare conductors transfer
all charges. 600 volt insulation blocks charge transfer. In
my experience, 1000v insulation blocks most charge transfer.
I use something called "Quietflex" that has 1000v insulation.
Most of the precipitation static doesn't transfer to
the antenna wire while RF waves/photons flow right
through the insulation with little attenuation. I suspect
plastic encased antennas are quieter than bare antennas.
There is a wealth of information on precipitation static
on the web, a lot of it having to do with antennas on
airplanes. Folding and insulating are two ways they have
solved the problem.
Folding or insulating your vertical may or may not be
feasible. If you solve your problem, please share it with
us here.
--
73, Cecil
http://www.w5dxp.com