On 1/23/2014 8:44 AM, Herbert Schonbohm wrote:
Some would argue that putting ground rods at the end of radials
doesn't really help.
Right. Really bad idea. We do NOT want current flowing in lossy earth.
The function of radials is to SHIELD the antenna from lossy earth and to
provide a return for antenna current and the fields the antenna
produces. Also, the end of the radial is a high impedance point. Adding
a ground rod messes up the current distribution on the radial, and
increases loss.
In most cases you can do well, perhaps better with #12 or #14 THHN
insulated wire laying on the ground. You will only then need about
90-100 feet for each radial due to the velocity factor of the wire
itself. If you run out of space due to your lot size you can run the
ends at right angles. It is important that the ends are not grounded.
IMHO what you are trying to do is cause the ground system currents to
travel in those wires rather than being dissipated in the earth thus
improving the system efficiency. You can pin the wires down with large
galvanized nails, , pounded into the ground after a single turn around
them. (U clips are also available by the hundred lot from
DX-Engineering) Normally after two weeks the sod will cover them and
they will be invisible and allow the lawn mower to pass over without a
snag.
All of this is very good advice.On-ground radials are as good as buried
radials -- the only reason to bury them is to protect them from foot
traffic. In general, with on-ground radials, more is better and length
is not critical.
73, Jim K9YC
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