| |
for any heading, it doesn’t interfere with the
instrument’s practical value.
Most shipboard installations consist of one or
more master gyros located in close proximity to
the steering station. The indications of the gyro
are transmitted electrically to repeaters located on
the bridge wings, at conning stations, and at other
necessary points.
Despite the excellence of the gyro mechanism,
the magnetic compass (NOT the gyro) is standard
equipment aboard ships. Since the gyrocompass
is powered by electricity, it would be useless if the
ship experienced a power loss. The gyrocompass
is also an extremely complicated, expensive, and
delicate instrument that is subject to mechanical
failure. Some gyros, for instance, become erratic
after a ship makes a series of sharp turns at high
speeds. For this reason, the magnetic compass
remains the reliable standby. It constantly checks
the performance of the gyrocompass and stands
ready at all times to take over if the gyrocompass
fails.
MAGNETIC COMPASS
The magnetic compass, which is the standard
compass on Navy ships, operates through the
magnetic attraction of the earth itself.
The magnetic compass is located in the pilot-
house. It consists of a magnetized compass needle
attached to a circular compass card that is usually
7 1/2 inches in diameter. Although the card
appears to move, it actually remains stationary
while pointing to the earth’s magnetic pole. In
reality, the ship is moving under the compass
card.
For the magnetic compass to give reliable
service, it must be properly installed, maintained,
and
protected
from
disturbing
magnetic
influences.
COMMUNICATION AND RADAR
ANTENNAS
From an operational standpoint, communica-
tion and radar antennas are a vital part of a ship’s
equipment. The communication antennas provide
us with command and control capability. Radar
antennas are used to electronically search the sea
and sky to detect objects beyond visual range.
They are also used as navigational aids and for
fire control purposes.
The function of a receiving antenna is to
intercept a portion of the electromagnetic wave
emitted by a transmitting antenna. The function
of a transmitting antenna is to convert the radio
frequency fed to it by a high-voltage generator
into an electromagnetic wave that may be
propagated to distant points. Radar antennas both
transmit and receive; some communication
antennas also have that capability.
Whatever their purpose, antennas are located
so that they receive the least possible amount of
interference from each other and from the ship’s
structure. Most of the masts, stacks, and other
structures abovedeck are grounded to the ship’s
hull and, through the hull, to the water. For an
antenna to obtain adequate coverage, it must be
installed so that the electromagnetic radiation
pattern from grounded structures causes mini-
mum distortion. Radar antennas usually rotate
and are normally mounted on platforms.
Also associated with the radar are radar
repeaters. While not actually a radar, they receive
input from a radar. They are located in different
areas from the radar, such as on the bridge or in
the combat information center.
Some typical shipboard communication
antennas include wire, whip, and high-frequency
antennas. Wire and whip antennas are designed
to operate through frequencies in the medium to
high range. Ships need various types of antennas
to ensure their use of the widest possible range
of available frequencies consistent with available
space.
SUMMARY
In this chapter you have learned about various
external equipment found aboard naval ships.
Any ship, no matter what its mission, must be
capable of mooring or anchoring. Hence, all ships
must have ground tackle.
Hopes are that survival equipment will never
be needed; however, all ships must have
appropriate survival gear available.
18-7
|
