Harris Maxiva ULX COFDM Series, Technical Manual

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10/6/10 888-2629-200 C-3
WARNING: Disconnect primary power prior to servicing.
Maxiva ULX COFDM Series
Peripheral Equipment Grounds. All peripherals are supplied with a separate grounding
wire or strap. All branch circuit receptacles must permit connection to this ground. This
service ground must be connected through the branch circuit to a common grounding
electrode by the shortest and most direct path possible. This is a safety ground
connection, not a neutral.
Often, circuit common in test equipment is connected to power ground and chassis. In
these cases, isolated AC power must be provided from a separate isolation transformer
to avoid a ground loop.
C.2.3 DC Ground
DC grounds in the transmitter are connected to a ground bus, which in turn is routed to
a common cabinet ground and then connected to an earth ground. The use of separate
ground busses is a suggested method of isolation used to prevent cross-coupling of
signals. These ground buses are then routed to the cabinet ground and to earth ground.
C.2.4 Earth Ground
The transmitter must be connected to earth ground. The connection must have an
impedance of 5 ohms or less. For example, a one-inch metal rod driven 20 feet into
moist earth will have a resistance of approximately 20 ohms, and a large ground
counterpoise buried in moist earth will exhibit a resistance on the order of 1 to 5 ohms.
The resistance of an electrode to ground is a function of soil resistivity, soil chemistry
and moisture content. Typical resistivity of unprepared soil can vary from
approximately 500 ohms to 50kohms per square centimeter.
The resistance of the earth ground should be periodically measured to ensure that the
resistance remains within installation requirements.
C.2.5 RF Ground
Electrical and electronic equipment must be effectively grounded, and shielded to
achieve reliable equipment operation. The facility ground system forms a direct path of
low impedance of approximately 10 ohms between earth and various power and
communications equipment. This effectively minimizes voltage differentials on the
ground plane to below levels which will produce noise or interference to
communication circuits.
The basic earth electrode subsystem consist of driven ground rods uniformly spaced
around the facility, interconnected with 2 or 4 inch copper strap. The strap and rods
should be placed approximately 40 inches (1 meter) outside the roof drip line of the
structure, and the strap buried at least 20 inches (0.5 meters). The ground rods should be