----- Original Message -----
From: "Keith Dutson" <kjdutson@earthlink.net>
To: <towertalk@contesting.com>
Sent: Monday, January 17, 2005 9:32 AM
Subject: RE: [TowerTalk] There's 'ground', and then there's 'ground'
>
> I read Polyphaser's technical note before installing my system. There is
a
> lot of discussion about soil conductivity and how adding more rods will
> improve conductivity. Do you have an idea of HOW MUCH impedance would be
> reduced?
>
> Keith NM5G
There's a heck of a lot of details that can go into this, but, it's easy to
establish the BEST that you can do, in a relative sort of way.
If the rods are "far" apart (basically on the order of 2 rod lengths), then
they're essentially independent, so the resistance of N rods in parallel is
the resistance of one rod divided by N. (assuming same soil conditions,
etc.)
If the rods are closer together, you get less improvement, culminating in
the situation where the rods are right next to each other, when the
resistance isn't much lower than a single rod.
The other factor to consider is the inductance of the wire(s) going to the
rod(s). 1 microhenry per meter is a nice rule of thumb number to use for an
isolated conductor... it might be twice or three times that, or half or a
third, but it probably won't be 10 uH/meter or 0.1 uH/meter..
You can also bury rods horizontally... To a first order, it's surface area
in contact with the soil that's the important thing.
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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