reradiation of energy to prevent or degrade the reception of
information by a receiver. The jamming function is tied directly to
the information provided by the EW support measures (ESM) component
of the EW program.
The tactics for using jamming vary with the
tactical situation and the commander's plan of action. Conceptually,
the jamming transmitter is placed between the signal transmitter and
the receiver to which the transmission is directed.
ability to place the jammer between the transmitter and the receiver
is seldom possible.
Thus, many jammers have enough power to
Each is used to attack a different signal or
(1) Spot jamming is directed against a single or specific
frequency, while allowing adjacent frequencies to remain free of the
effects of the jamming.
It applies the full radiated power of the
(2) Barrage jamming targets multiple frequencies.
It may be
used over a large portion of the frequency spectrum or the entire
needs high power to operate. It cannot distinguish between enemy and
(3) Sweep jamming is
used to block several preselected
remaining on each frequency
for a predetermined period.
affect both friendly and enemy
b. Various types of signal modulation can be used during jamming.
These modulation types are selected based on their effectiveness
against the transmission being attacked. In some cases, the jammer's
signal generator can produce only a limited number of signals.
other cases, the generator can produce a large number of signals or
Some of the most commonly used modulation types are
(1) The stepped tone signal is a series
normally sent in an ascending or descending order.