aircraft, it is important for air traffic control to know not
only their location but their identity. The Selective
Identification Feature (SIF) was developed to expand
the IFF system. This increases its flexibility through a
multiple-code transponder reply. By such means,
selective and individual identification of aircraft is
possible, with the following results:
! Ground control of friendly aircraft
! Operational flexibility in the identification
process
! A measure of additional security in
identification
ELECTRONIC COUNTERMEASURES
A basic rule of warfare is that for each weapon used
by one side, a counter-weapon will be developed by the
other side. This rule is clearly seen in the development
and use of electronic countermeasures (ECM). The
objective of ECM is to gather intelligence from the
enemy's electronic devices and make the devices
ineffective. Electronic countermeasures consist of two
general types of actions—passive and active.
Passive
Passive ECM operations are those that cannot be
directly detected by the enemy. These include search
operations
where
enemy
radar
transmitters
are
detected,
located,
and
as
many
of
the
signal
characteristics
as
possible
are
determined.
For
example, ECM can detect a radar pulse transmission at
1 1/2 times the distance the radar return can detect a
target. The signal characteristics determine if the radar
is used for search, navigation, or fire control. Passive
countermeasures also include evasive tactics taken to
avoid detection and methods of controlling the
radiations from friendly equipment. Such measures
prevent the enemy from using the signals for homing,
direction finding, or any other purpose.
Active
Active ECM operations are actions that the enemy
can detect. Active operations prevent effective use of
the enemy's equipment. Electronic jamming interferes
with enemy radar and communications. Active radar
nonelectronic jamming is done by releasing strips of
metallic foil (chaff or window) from aircraft. The
falling strips cause many false targets or cause the
enemy scope to cover with clutter that can mask targets
from search and fire control radars.
Q7-24.
What is the meaning of the acronym radar?
Q7-25.
A radar is a device used to detect objects at
distances greater than the eye can see by the
use of what basic principle?
Q7-26.
Sound waves travel how many feet per
second?
Q7-27.
A system that allows a friendly aircraft to
identify
itself
automatically
before
approaching near enough to threaten other
naval units is known as what type of system?
Q7-28.
What
are
the
objectives
of
electronic
countermeasures?
ANTISUBMARINE WARFARE
EQUIPMENT (ASW)
LEARNING
OBJECTIVE:
Identify
the
purpose and uses of antisubmarine warfare
equipment to include sonobuoys and magnetic
anomaly detection equipment.
A major problem for the Navy is the detection of
enemy submarines. Submarine detection devices
include
(SOund
NAvigation
Ranging
(sonar),
sonobuoys, and Magnetic Anomaly Detection (MAD)
equipment. Surface ships, submarines, and harbor
defense installations use sonar equipment. Aircraft use
MAD equipment.
SONOBUOYS
The sonobuoy is an expendable electronic listening
device dropped into water from carrier-based and
land-based patrol aircraft. The sonobuoy detects
underwater sounds and transmits these sounds to
aircraft.
A surfaced or snorkeling submarine is not likely to
be detected by an aircraft's radar. The reason is the
submarine's ECM detects the aircraft's radar at a greater
distance than the aircraft can detect the submarine. The
sonobuoy helps solve the submarine detection problem.
The sonobuoy, housed in a cylindrically shaped tube, is
designed to float upright in the water. Upon being
dropped from an aircraft, the sonobuoy, stabilized by
small blades, enters the water in an upright position.
Upon striking the water, the stabilizing blades eject and
a small transmitting antenna erects itself. The impact
also causes the release of a hydrophone (underwater
microphone).
This
underwater
listening
device
connects to the end of a cable that permits it to sink to a
predetermined
depth.
The
hydrophone
receives
7-19
