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 MIL-HDBK-419A
(1)
all seriously degraded or damaged air terminals should be replaced;
(2) air terminals should be relocated as needed so that they are the objects of highest elevation on
the structure; and where they provide a 1:1 cone of protection for the antennas without affecting their
operation;
(3) down conductors should be rerouted or additional down conductors added where more direct
paths to the earth are needed (see Section 1.3.2.2);
(4) if not already provided, the lightning protection network should be interconnected with the
earth electrode subsystem, electrical ground, utility pipes, equipment grounds, and with the building ground to
provide common grounding for all;
(5) all corroded and mechanically damaged connectors and fasteners should be replaced with
UL-approved devices; and
(6)
missing and severely damaged guards should be replaced.
The lightning protection subsystem should be expanded as needed to provide protection for those
g.
parts of the facility extending outside the established cones of protection (see Section 1.3.2.1).
At those facilities where the lightning outage history indicates a need for surge protection on either
h.
signal or power lines, appropriate lightning and surge protectors should be installed. Insure that the protectors
are adequate for protecting the type of equipment on which installed (see Volume I, Section 10.4.2.3).
Review electrical wiring diagrams and the electrical equipment distribution within the facility to
i.
determine possible direct or indirect coupling paths between noisy equipments and susceptible electronic
apparatus. Apply corrective measures such as:
relocate equipments (see Section 1.9.1);
(1)
(2) redistribute the electrical load so that potentially interfering equipments are served by
separate feeders;
install electrical feeders in steel conduit or raceway to reduce magnetic fields; and
(3)
(4) relocate signal lines to sensitive equipments at the maximum possible distance from power
conductors feeding noisy equipments.
Correlate, if possible, any evidence of equipment malfunctions due to electrical noise on signal or
j.
control cables with the measured values of stray currents or voltages on grounding conductors and on cable
shields. If such correlation exists, determine as best as possible the probable cause of such noise voltages using
the principles set forth in Volume I, Chapters 5 and 6. Then, apply the techniques described in Sections 1.5, 1.8,
and 1.9 to reduce the noise to a level acceptable to the equipments in the facility.
2-34
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