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 MIL-HDBK-419A
Carefully review the drawings of the facility to identify the type of signal grounding employed
k.
throughout the facility, If operational experience as indicated by maintenance logs or outage reports and
operator comments reveal problems with system noise and interference attributable to grounding deficiencies,
review in detail Volume I, Chapters 5 and 6, and Section 1.5 of this volume. Based on this review and the
relative severity of the problems, choose the most appropriate noise minimization procedures and implement
them.
Where shielding deficiencies exist, determine if the need is for additional shielding or for improved
l.
maintenance of the existing shields. If no shielding is present, design and install shields as needed. See Section
1.8.1 for design assistance. If the existing shields have simply degraded through poor aperture control and poor
bond or seam maintenance, implement corrective measures immediately (see Sections 1.7 and 1.8 and also see
Sections 3.3 and 3.4).
m. If the structure is used as a lightning down conductor or as an electrical safety grounding conductor,
see that all joints are effectively bonded (see Section 1.7.1).
If more than 25 percent of the bonds measured exhibit a resistance greater than one milliohm (after
n.
the steps recommended in Step "d" of Section 2.2.2.2.2 are taken), all bonds throughout the facility should be
inspected carefully, and the resistance measured. Each one found deficient should be redone in accordance with
the recommendations set forth in Section 1.7.
Indicate all changes made during the upgrading process on the facility drawings.
o.
2.2.4 Expansion of Existing Facilities.
As operational requirements change, expansions of the grounding and shielding networks in a facility will be
necessary. When such actions are necessary, it is essential that the added elements maintain the philosophy and
integrity of the existing networks. When making additions or modifications to shielded areas, the original level
of shielding integrity must be maintained. Particular attention must be directed to the careful bonding of
connector shells, the installation of filters, and other practices which may drastically degrade the shielding
effectiveness of a housing or other enclosure if not controlled.
Following major additions to the facility, the facility should be resurveyed. Any deficiencies in the installation
or compromises to the original networks should be corrected. File a copy of all survey results in the
maintenance file for the facility to provide the initial starting point for the maintenance history. Finally
review all drawings to verify that they are complete and accurately reflect the actual installation.
2.2.5 Expansion of Existing Facilities for Higher Frequency Grounds.
Most existing communication facilities will require the addition of an equipotential plane to satisfy the
grounding requirements for frequencies above 30 kHz. When both higher and lower frequency requirements
must be met, a hybrid system may be required but in most cases the equipotential plane will suffice for both
requirements.
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