center or work group supervisory position. Your positive
attitude and confidence will be an asset, and in time, you
will become more proficient in managing the
maintenance for the additional equipment and systems.
It is almost impossible to become a proficient
technician in all electronic equipments and systems;
however, as a supervisor, you should have adequate
knowledge of all the electronic equipments and systems
for which you are responsible. Additionally, you should
have at least a functional knowledge (as a minimum) of
all peripheral, ancillary, and supporting equipment and
systems.
As a supervisor, you should know where all
equipments are located, their designations, and their
position numbers. Your casualty control folder should
help you find equipment locations. With time, as you
apply yourself as a conscientious supervisor, identifying
and explaining locations, functions, and system
operation will become second nature for you.
A good background knowledge of all equipments
and systems combined with your maintenance
experience and positive and confident attitude will be
assets as you work in the following areas:
. Training your technicians (and yourself)
. Minimizing equipment and system downtime
l Providing support to the ship’s overall mission
In addition, you will also earn the confidence and
support of your subordinates and the confidence and
support of your seniors.
ELECTROMAGNETIC
INTERFERENCE (EMI)
EMI is an electromagnetic or electrostatic
disturbance that causes electronic equipment to
malfunction or to produce undesirable responses or
conditions that do not meet the requirements of
interference tests. The dramatic increase in the types of
electronic and electrical equipment since the beginning
of World War II has brought about a problem that was
given little consideration in previous years-EMI. EMI
has become a problem because naval ships and aircraft
now contain a large number of complex, sensitive
devices that are not always compatible with one another.
As an ETl or ETC, you must be aware of the
problems caused by EMI and of the solutions to these
problems. No magic is involved in reducing or
eliminating EMI; instead, problems are resolved by
using everyday, commonsense approaches to main-
taining equipment.
SOURCES OF EMI
There are three types (or sources) of
electromagnetic interference: natural, inherent, and
man-made.
Natural EMI
Natural interference is caused by natural events,
such as snow storms, electrical storms, rain particles,
and solar radiation. This type of interference is
commonly called static or atmospheric noise. It can
cause problems with rf communications and older data
links between shore, ship, and air; however, it does not
cause many problems with modern digital data
equipment.
Inherent EMI
Inherent interference is noise within a piece of
electronic equipment, caused by thermal agitation of
electrons flowing through circuit resistance. (This noise
is usually noticed as the background noise heard in a
radio receiver when it is tuned to a frequency between
stations.)
Man-Made EMI
Man-made EMI is produced by a number of
different classes of electrical and electronic equipment.
They include, but are not limited to: transmitters,
welders, power lines, motors and generators, lighting,
engines and igniters, and electrical controllers. These
devices can cause severe EMI, which can degrade the
operation of shipboard or shorebased data processing
equipment.
The discussion of EMI will be directed to the
recognition and elimination of the man-made EMI that
you are apt to encounter ashore or afloat.
TYPES OF EMI
EMI can be classified by its spectrum distribution.
EMI can be either narrowband or broadband
interference. These terms refer to the frequency
spectrum the interference covers.
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