Ufer grounds:
The question of grounding comes up often, and it's important to
distinguish between the various functions of a ground for a ham station.
They are
1) Safety (utility) ground. This is the solid connection to the ground
wire from the AC service entrance. All equipment enclosures must be
bonded to this ground so that if leakage occurs from a hot wire to a
chassis (etc.) the enclosure will not become hot with AC. Note that the
grounding of the service entrance itself is important.
2) Lightning ground. This is the connection of antennas, towers, and
lghtning suppression devices to a low-impedance ground to divert induced
potentials and even direct strikes (if the system is built properly). A
lightning ground needs to be implemented with a single entrance panel
and appropriate suppressors on all incoming lines, including antenna,
power, telephone, rotor, etc. in order to be effective.
3) RF ground. This is the 'ground return' for antenna currents. Some
antennas (balanced ones) do not need an RF ground at all. Others (e.g.
simple verticals) need an elaborate one. Normally the ground systems
used for 1) and 2) are NOT effective as RF grounds, although all ground
systems should be bonded together.
4) Common potential ground. All equipment on an operating desk should
be connected by short wide straps to a common ground bus (not daisy
chained), which is connected to the other grounds. This helps reduce
hum, noise, and RF getting into equipment.
A Ufer ground can be used to ground the service entrance or as part of a
lightning ground system. If it happens to be located near the base of a
simple vertical or random wire it can be connected to the radial system
and be helpful as part of the RF ground system. It isn't especially
useful as an RF ground otherwise.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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