FM 24-33

Preface

Purpose and Scope

This manual concentrates on the defense against enemy efforts to disrupt
or destroy our effective use of the electromagnetic spectrum for communications.
Following the techniques in this manual will increase our chances for success
on the AirLand battlefield.
The communications electronic counter-countermeasures (ECCM) in this
manual will assist commanders, staff personnel, and radio operators. This
manual will also assist signal officers and electronic warfare (EW) personnel.
The techniques in this manual are proven; however, they are not all inclusive.
Maintaining effective, friendly communications on the AirLand battlefield will
depend on our ability to enhance proven ECCM techniques.
This manual amplifies the EW doctrine in FM 100-5 and FM 24-1.
Appendix D gives instructions for implementing ECCM for radio systems.
User Comments
The proponent of this publication is HQ TRADOC. Your comments on this
publication are encouraged. Submit changes for improving this publication on DA
Form 2028 (Recommended changes to Publications and Blank Forms) and key them to
pages and lines of text to which they apply. If DA Form 2028 is not available,
a letter is acceptable. Provide reasons for your comments to ensure complete
understanding and proper evaluation. Forward your comments to Commander, United
States Army Signal Center and Fort Gordon, ATTN: ATZH-DTL, Fort Gordon,
Georgia 30905-5075.

iii
 FM 24-33

Chapter 1
Electronic Counter-Countermeasures in Defense
Planning

1-1. Introduction
a. Since the beginning of this century, we have been developing
electronic devices for military purposes. These purposes include--
Communicating.
Detecting.
Navigating.
Identifying targets.
Countering and monitoring hostile use of the electromagnetic
spectrum.
Retaining friendly use of the spectrum.
b. Electronic warfare (EW) uses electromagnetic energy to determine,
exploit, reduce, or prevent hostile use of the electromagnetic spectrum. It
also involves actions taken to retain friendly use of the electromagnetic
spectrum. Figure 1-1 shows the three categories of EW:
Electronic warfare support measures (ESM).
Electronic countermeasures (ECM).
Electronic counter-countermeasures (ECCM).
3
Command, control, and communications (C CM) integrates
operations security (OPSEC), military deception, jamming, and physical
3
destruction. Using this integration and supported by intelligence, C CM denies3
information to the enemy and influences,
3
degrades or destroys
3
the enemy's C
capabilities. At the same time, C CM protects friendly C . ECCM reduces or3
eliminates the effects of hostile attempts to degrade or disrupt friendly C .

1-1
FM 24-33

1-2
 FM 24-33

c. Increased mobility and technical advances force commanders and staff

to view the modern battlefield faster and clearer than before. Our units depend
on effective communications to ensure the flow of critical command, control,
intelligence, fire support, and service support orders and information.
Therefore, commanders, staff, and radio operators must know and practice sound
communications ECCM techniques.
1-2. Radio Electronic Combat
a. Most potential enemies of the US are trained in Soviet military
doctrine; therefore, the following paragraphs address Soviet doctrinal
approaches. To practice sound ECCM techniques, we must understand the threat to
our continued use of the electromagnetic spectrum. Radio electronic combat
(REC) is one such threat. REC is the total integration of EW and physical
destruction resources to deny us the use of our electronic control systems.
It also protects friendly electronic control systems from disruption by the
enemy. Our potential enemies consider REC integral to all combat actions. They
have made major investments in developing techniques and equipment to deny
enemies the effective use of the electromagnetic spectrum for communications.
b. The purpose of REC is to disrupt or destroy our command and control
systems at the most advantageous time. A goal of REC is to disrupt or destroy
at least 60 percent of our command, control, intelligence, and weapons system
communications: 30 percent by jamming and 30 percent by destructive fires. To
accomplish this goal, enemy forces expend considerable effort and resources to
gather combat information about their enemies. As locations are determined and
units are identified, enemy forces establish priorities as follows:
To fire suppressive fires.
To jam communications assets.
To deceptively enter radio nets.
To interfere with the normal flow of their enemy’s communications.
1-3. Commander’s Responsibilities
a. Because REC is a real threat on the modern battlefield, commanders
at all levels must ensure their units are trained to practice sound ECCM
techniques. The information in this manual is a basis for this training. ECCM
is a command responsibility. The greater the command emphasis given ECCM, the
greater the benefits in terms of casualty reduction and combat survivability in
a hostile environment.

1-3
FM 24-33

b. In addition to ensuring their units are trained to practice sound

ECCM techniques, commanders must constantly measure the effectiveness of the
ECCM techniques. They must also consider ECCM while planning tactical
operations. Commanders may accomplish these objectives by--

(1) Reviewing all after-action reports where jamming or deception was

encountered and assessing the effectiveness of the defensive ECCM.
(2) Ensuring all encounters of interference, deception, or jamming are
reported and properly analyzed by the signal officer and the G2/S2.
(3) Analyzing the impact of enemy efforts to disrupt or destroy friendly
command and control communications systems on friendly operations plans.
(4) Ensuring the unit practices communications security (COMSEC)
techniques daily. Units should practice--
Changing call signs and frequencies often, but only in accordance
with the signal operation instructions (SOI).
Using approved encryption systems, codes, and authentication
systems.
Controlling emissions.
(5) Making equipment ECCM requirements known through quick-reaction
capabilities as outlined in AR 105-7.
(6) Ensuring radios with mechanical or electrical faults are repaired
quickly. This is one way to reduce radio distinguishing characteristics.
(7) Practicing net discipline.
1-4. Staff Responsibilities
a. The military staff is organized to assist the commander in
accomplishing the mission. Specifically, the staff is organized and operates to
respond immediately to the commander and subordinate units. The staff should--
(1) Keep the commander informed.
(2) Reduce the time to control, integrate, and coordinate operations.
(3) Reduce the chance for error.
(4) Relieve the commander of supervisory details in routine matters.

1-4
 FM 24-33

b. All staff officers provide information, furnish estimates, provide

recommendations, prepare plans and orders, and supervise. Staff members should
assist the commander in carrying out communications ECCM responsibilities.
(1) The G3/S3--
Exercises staff responsibility for ECCM.

Includes ESM and ECM play in all command post and field training
exercises and evaluates ECCM techniques employed.
Includes ECCM training in the unit training program.
(2) The G2/S2--
Advises the commander of enemy capabilities that could be used to
deny the unit the effective use of the electromagnetic spectrum.
Keeps the commander apprised of the unit’s signal security posture.
(3) The signal officer--
Prepares and conducts the unit ECCM training program.
Ensures there are alternate means of communications for those
systems most vulnerable to enemy jamming.
Ensures available COMSEC equipment is distributed to those systems
most vulnerable to enemy information gathering activities.
Ensures measures are taken to protect critical friendly frequencies
from intentional and unintentional interference.
Evaluates interference and prepares follow-up meaconing, intrusion,
jamming, and interference (MIJI) reports.
Enforces proper use of radiotelephone, ECCM, and transmission
security procedures on communications channels.
Performs frequency management duties and issues SOI booklets on a
timely basis.
Prepares and maintains a restricted frequency list of taboo,
protected, and guarded frequencies.
Prepares the ECCM and restricted frequency list appendices to the
signal annex with appropriate cross-references to the other annexes (EW, OPSEC,
deception) and to the SOI for related information.

1-5
FM 24-33

1-5. Planning Categories

The enemy threat to our communications must be assessed during the
planning process. We must plan to counter the enemy’s attempts to take
advantage of the vulnerabilities of our communications systems. As a minimum,
four categories of ECCM planning must be considered: deployment, employment,
replacement, and concealment.
a. Deployment.
(1) Geometry.

(a) We must analyze the terrain and determine methods to make the
geometry of the battlefield work in our favor. Adhering rigidly to standard
command post deployment makes it easier for the enemy to use the direction
finder (DF) and aim his jamming equipment at us. Our command post vulnerability
to enemy DF efforts can be greatly reduced by incorporating tactical satellite
systems. We also tend to deploy our units and communications systems
perpendicular to the forward line of own troops (FLOT). This greatly enhances
the enemy’s ability to intercept our communications because we aim our
transmissions in the enemy’s direction. As much as possible, we must install
our terrestrial line-of-sight communications parallel to the FLOT. This will
keep the primary strength of our transmissions in friendly terrain. (See Figure
1-2.) Tactical satellite communications systems are relieved of this constraint
because of their inherent resistance to enemy DF efforts. Terrain features
should be used when possible to mask friendly communications from enemy
positions. This may mean moving senior headquarters farther forward and using
more jump or tactical command posts so that commanders can continue to direct
their units effectively.
(b) Locations of command posts must be carefully planned. Command post
locations generally determine antenna locations. The proper installation and
the siting of antennas around command posts are critical. Antennas and emitters
should be dispersed and remoted so that all a unit’s transmissions are not
coming from one central location.
(2) System design.
(a) In designing the communications system, we must establish alternate
routes of communications. This involves establishing enough communications
paths so that the loss of one or more routes will not seriously degrade the
overall system. The commander establishes the priorities of critical
communications links. The higher priority links should be afforded the greatest
number of alternate routes.

1-6
 FM 24-33

(b) Three routing concepts or some permutation of them can be used in

communications: straight line, circular, and grid. (See Figure 1-3. ) The
straight-line system gives no alternate routes of communications. The circular
system gives one alternate route of communications. The grid system gives as
many alternate routes of communications as can be planned practically. Any
combination of the three routing concepts may be used to establish the
communications system that best supports the mission.
(c) Normally, the grid routing system allows the greatest number of
alternate routes of communications. These alternate routes can enable our units
to continue to communicate in spite of the enemy’s efforts to deny us the use
of our communications systems. They can also be used to transmit false messages
and orders on the route that is experiencing interference while they transmit
actual messages and orders through another route or means. A positive benefit
of continuing to operate in a degraded system is that it will cause the enemy
to waste assets that might otherwise be used to impair our communications
elsewhere.

1-7
FM 24-33

b. Employment.
(1) We must plan to avoid establishing a pattern of communications.
Enemy intelligence analysts are highly trained to extract information from the
pattern as well as the text of our transmissions. If easily identifiable
patterns of friendly communications are established, the enemy can gain
valuable information.
(2) The number of friendly transmissions tends to increase or decrease
according to the type of tactical operation being executed. Plans that prevent
enemy intelligence analysts from using these increases and decreases as
intelligence should be included in the battlefield deception plan.
This can be done by using false peaks or traffic leveling. False peaks are
created by preplanning increases in transmission traffic on a random schedule.
Tactically, traffic leveling is done by preplanning messages to be sent when
there is a decrease in transmission traffic. Thus, traffic leveling is used to
keep the transmission traffic fairly constant. False peaks are used to prevent
the enemy from connecting an increase of communications with a tactical
operation. Messages transmitted for traffic leveling or false peaks must be
coordinated to avoid operational security violations, mutual interference, and
confusion among our equipment operators.

1-8
 FM 24-33

(3) The SOI resolve many of the problems concerning communications

patterns. They allow us to change call signs and frequencies often and at
random. This has long been recognized as a key in confusing enemy traffic
analysts. The more we change frequencies, call signs, locations, and operators,
the more confused enemy traffic analysts become. The enemy uses our SOPs to
help perform his mission. We must ensure these procedures have enough
flexibility to avoid establishing communications patterns.
c. Replacement.
(1) Replacement is establishing alternate routes and means of doing what
the commander requires. FM voice communications are the most critical
communications used by the commander during enemy engagements. As much as
possible, critical systems should be reserved for critical operations. The
enemy should not have access to information about our critical systems until
the information is essentially useless.
(2) Alternate means of communications should be used before enemy
engagements. This ensures the enemy cannot establish a data base to destroy our
primary means of communications. Primary systems must always be replaced with
alternate means of communications if the primary means become significantly
degraded. These replacements must be preplanned and carefully coordinated;
otherwise, the alternate means of communications could be compromised and
become as worthless as the primary means. Users of communications equipment
must know how and when to use the primary and alternate means of
communications. This ensures the most efficient use of our communications
systems.
d. Concealment. As much as possible, operation plans should include
provisions to conceal communications personnel, equipment, and transmissions.
It is difficult to effectively conceal most communications systems. Antennas
must have access to free space. However, communications equipment can be
concealed by installing antennas as low as possible on the back side of terrain
features and behind man-made obstacles. This helps conceal the equipment while
still permitting communications.
1-6. Electronic Counter-Countermeasures and Signal Security
a. ECCM and signal security are closely related. They are defensive
arts based on the same principle. If the enemy does not have access to our
essential elements of friendly information (EEFI), he is much less effective.
The goal of signal security is to ensure the enemy cannot exploit the friendly
use of the electromagnetic spectrum for communications. Signal security
techniques are designed mainly to give commanders confidence in the security of
their transmissions. The goal of practicing sound ECCM techniques is to ensure
the continued effective use of the electromagnetic spectrum. Signal security
and ECCM should be planned based on the enemy’s ability to gather intelligence
and degrade our communications systems.

1-9
FM 24-33

b. We must ensure effective employment of all communications equipment

by tactical commanders in spite of the enemy’s concerted efforts to degrade our
communications to his tactical advantage. Modifying and developing equipment to
make our communications less susceptible to enemy exploitation is an expensive
process. Equipment that will solve some of our ECCM problems is being developed
and fielded. However, the burden of security and the burden of continued
operation of all communications equipment are on the commander, staff planners,
and radio operators.
c. Operators of communications equipment must know the impact of
jamming and deception on our communications. Incorrect operating procedures can
jeopardize the unit’s mission and ultimately increase unit casualties.
Operators must instinctively use preventive and remedial ECCM techniques.
Maintenance personnel must know that improper modifications to equipment may
cause the equipment to develop peculiar characteristics that can readily be
identified by the enemy. Commanders and staff must develop plans to ensure the
continued use of our communications equipment and systems. They must also be
able to evaluate MIJI and after-action reports so that appropriate remedial
actions can be initiated. It all starts with good training. FM 25-100 discusses
proper training techniques.
d. ECCM should be preventive. In planning communications, we should
consider the enemy capabilities to deny us the effective use of our
communications equipment. ECCM should be planned and applied to force the enemy
to commit more jamming, information gathering, and deception resources to a
target than it is worth or than he has readily available. ECCM techniques must
also force the enemy to doubt the effectiveness of his jamming and deception
efforts.
1-7. Emission Control
The key to successful defense against the enemy’s attempts to destroy or
disrupt our communications is the control of our electromagnetic emissions.
Transmitters should be turned on only when needed to accomplish the mission.
The enemy intelligence analyst will look for patterns he can turn into usable
information. If our transmitters are inactive, the enemy has nothing to work
with as intelligence. Emission control can be total. For example, radio silence
or radio listening silence may be directed by the commander whenever desired.
Emission control should be habitual. Transmissions should be kept to a minimum
(20 seconds absolute maximum, 15 seconds maximum preferred) and should contain
only information critical to the mission. Good emission control makes using
our communications equipment appear to be without pattern and is therefore
consistent with good ECCM practices. This technique alone will not eliminate
the enemy’s ability to direction find a friendly transmitter but, when combined
with other ECCM techniques, it will make locating a transmitter more difficult.
(See Figure 1-4.)

1-10
FM 24-33

1-11
 FM 24-33

Chapter 2
Preventive Electronic Counter-Countermeasures
Techniques

2-1. Introduction
a. We must use preventive ECCM techniques to safeguard our
communications from enemy disruption and destruction. ECCM techniques include
all measures taken to avoid enemy detection and to deny enemy intelligence
analysts useful information. There are two categories of preventive ECCM
techniques:
ECCM designed circuits (equipment features).
Radio system installation and operating procedures.
Radio operators have little control over the effectiveness of ECCM designed
circuits; therefore, the primary focus of this manual is radio system
installation and operating procedures.
b. Reducing the vulnerability of our communications to enemy efforts to
disrupt or destroy them is largely a matter of avoiding detection by the enemy.
If the enemy cannot detect our communications, he will have difficulty
disrupting or destroying them. Effective jamming depends on knowing the
frequencies and approximate locations of units to be jammed. We must do all we
can to prevent disclosing this information. Using the techniques in this
chapter will help accomplish this. Table 2-1 lists preventive ECCM techniques.
2-2. Minimal Transmissions
a. The most effective preventive ECCM technique is to minimize radio
transmissions and transmission times. Even though normal day-to-day operations
require radio communications, these communications should be kept to the
minimum needed to accomplish the mission. Using the following preventive ECCM
techniques will minimize transmissions and transmission times.
(1) Ensure all transmissions are necessary. Analysis of US tactical
communications indicates that most communications used in training exercises
are explanatory and not directive. Radio communications must never be used as a
substitute for complete planning. Tactical radio communications should be used
to convey orders and critical information rapidly. Execution of the battle must
be inherent in training, planning, ingenuity, teamwork, and established and
practiced SOPs. The high volume of radio communications that usually precedes a
tactical operation makes the friendly force vulnerable to enemy interception,
direction finding, jamming, and deception.
NOTE: Even when communications are secure, the volume of radio
transmissions can betray an operation and the enemy can still
disrupt or destroy our ability to communicate.

2-1
FM 24-33

2-2
 FM 24-33

(2) Preplan messages before transmitting them. The radio operator should
know what he is going to say before beginning a transmission. When the
situation and time permit, the message should be written out before beginning
the transmission. This will minimize the number of pauses in the transmission
and decrease transmission time. It will also help ensure the conciseness of the
message. The Joint Interoperability of Tactical Command and Control Systems
(JINTACCS) voice templates are some of the best tools a RATELO can use to
minimize transmission time.
(3) Transmit quickly and precisely. When a transmission is necessary,
the radio operator should--
Speak in a clear, well-modulated voice.
Use proper radiotelephone procedures.
This is especially critical when the quality of communications is poor. This
minimizes the chances that a radio transmission will have to be repeated.
Unnecessary repetition increases transmission time and the enemy’s opportunity
to intercept our transmissions and thus gain valuable information.
(4) Use equipment capable of data burst transmission. This is one of the
most significant advantages of tactical satellite communications systems. When
messages are encoded on a digital entry device for transmission over satellite
systems, the transmission time is greatly reduced.
(5) Use an alternate means of communications when possible. Alternate
means of communications, such as cable, wire, or organic soldiers performing as
messengers, can be used to convey necessary directives and information. Radio is
a convenient means of communications; however, convenience does not justify
making a radio transmission. Other means of communications must be used when
practical.
b. We must not operate our radios unnecessarily. Minimizing
transmissions will safeguard our radios for critical transmissions. The enemy
cannot effectively disrupt or destroy our communications without first
gathering information from our radio transmissions. This does not advocate
total, continuing radio silence; it advocates minimum transmissions and
transmission times. We must never forget that operating our radios
unnecessarily increases the enemy’s opportunities to gather information.
2-3. Transmission Protection
All radio communications systems consist of antennas, receivers, and
transmitters. A transmitted signal can be received by any radio station with
which it is compatible. However, the receiving and transmitting radio stations
must be set to the same frequency, and the receiving antenna must receive a
strong enough signal to activate the receiver. If these criteria are met, any

2-3
FM 24-33

receiver-- friendly or enemy-- can intercept a transmitted signal. Therefore,

protecting our transmissions must be our goal. We can reduce the possibility of
our transmissions being intercepted by properly selecting and properly
installing our radio systems. This applies to secure and nonsecure
communications. Practicing the following preventive ECCM techniques will reduce
the strength of the signals being transmitted toward the enemy.
a. Use low power. Power controls and antennas are closely related. The
strength of the signal transmitted by an antenna depends on the strength of the
signal delivered to it by the transmitter. The stronger the signal, the farther
it travels. A radio communications system must be planned and installed to
allow those stations that have a need to communicate with each other to do so.
In carefully planned and installed communications systems, we can usually
operate on low power. Using low power decreases the range and makes it more
difficult for the enemy to detect and intercept our transmissions. It also
reserves our high power for burning through enemy jamming.
b. Select the proper antenna. The range of a transmission depends on
having a usable frequency and on two equipment-related factors:
The power output of the transmitter.
The antenna selected for use with a given radio.
The characteristics and orientation of an antenna affect the strength of the
signal transmitted in all directions. An antenna should be selected and
installed to ensure that a radio station can communicate with those radio
stations with which it needs to communicate. It should also be selected to
minimize the strength of the signal transmitted in the direction of the enemy.
This can be accomplished by observing the following rules in the selection and
the installation of our antennas.
(1) Select the antenna with the shortest feasible range capability.
Almost every US Army radio will operate with two or more different kinds of
antennas. For example, either the short whip, the long whip, or the OE-254
antenna may be used with the Radio Set AN/PRC-77. The short whip antenna has
the shortest range. The OE-254 has the longest range. The antenna used with a
given radio should be the one with the shortest range that still permits good
communications with all radio stations with which that radio station must
communicate. This decreases the chances of enemy interception and reserves
longer range antennas for use in overcoming enemy jamming.
(2) Use directional antennas. The three types of antennas are--
Omnidirectional.
Bidirectional.
Unidirectional.

2-4
 FM 24-33

Omnidirectional antennas transmit radio waves in all directions; however, they

are more vulnerable to enemy information gathering, jamming, and deception than
bidirectional and unidirectional antennas. Bidirectional antennas transmit
radio waves in two directions. This enables us to communicate with two or more
radio stations in opposite directions. They are good for lateral communications
along the FLOT and should, when possible, be positioned so that transmission
paths are parallel with enemy lines. Positioning the antenna in this way
reduces the possibility of the enemy intercepting our communications. The
unidirectional antenna can transmit and receive best in only one direction.
When it is positioned properly, this antenna is the least vulnerable to enemy
information gathering, jamming, and deception. FM 24-18 explains installation
of directional antennas. Tactical satellite communications terminals should be
installed to allow the terminal to communicate through the satellite with other
terminals in its net.
c. Select a site that masks transmitted signals from enemy
interception.
(1) When possible, the antenna should be positioned so that a terrain
feature or man-made obstacle is between the antenna and the enemy. The antenna
should be positioned as low as possible on the side of terrain features or
man-made obstacles away from the enemy. This decreases the range of the
transmitted signal and scatters the signal in the direction of the enemy. It
makes our transmissions less vulnerable to enemy direction finding and
detection. Also, by masking our transmissions from enemy interception, we
safeguard our antennas against enemy information gathering, jamming, and
deception efforts.
(2) An antenna can be properly positioned even when a station must
communicate with a friendly station located between it and the enemy. Using
terrain features or man-made obstacles to mask transmissions only reduces the
range of the transmitted signal in the direction of the enemy; it does not stop
i t . The optimum siting for an antenna must be determined on a case-by-case
basis.
d. Use mobile antennas. Frequent relocations of our antennas make
accurate enemy direction finding more difficult and effective enemy jamming
less likely. Antennas in the vehicular or man-pack configurations can be
quickly and easily displaced. Even the ground plane antenna can be made mobile
by mounting it on a vehicle and securing it by guy wires. This provides a
mobile antenna that can be relocated rapidly. If this cannot be done, ensure
the antenna is remoted from the communications equipment.
e. Use decoy antennas. When practical , additional antennas can be used
as decoys and set up in credible antenna locations. Enemy intelligence analysts
place special emphasis on photographs or reconnaissance reports of visible
antenna arrays. Decoy antennas may cause the enemy to expend his limited
resources against an unworthy target, thus allowing us to maintain worthy
communications.

2-5
FM 24-33

Use steerable null antenna processors. The Steerable Null Antenna

Processor (SNAP-1) Group OL-257()/VRC is designed for use with the AN/VRC-12
family of radios and in the nonhopping mode of the Single-Channel Ground and
Airborne Radio System (SINCGARS). It provides ECCM protection for the
single-channel combat net radios in the VHF range (30-88 MHz). It will operate
efficiently when the operator has no prior knowledge of the direction of either
the unwanted or desired signal. It has a bypass or override feature that can be
used in a jam-free environment or when equipment fails. The SNAP-1 will process
the desired signal to its attached receiver even if the sending transmitter is
not equipped with the SNAP-1. The SNAP-1 will be doctrinally employed on
essential command and control and fire support single-channel radio nets from
platoon to division level in forward areas. FM 24-18 contains a more detailed
explanation of steerable null antenna processors.
2-4. Radiotelephone Operator Procedures
The RATELO is the key to the success of preventive ECCM techniques. The
RATELO ensures that radio transmissions are minimized and protected, thereby
preventing the enemy from intercepting and disrupting or destroying our
communications. Besides practicing the preventive ECCM techniques, the RATELO
must practice procedures that minimize the usable information transmitted. This
prevents the enemy from disrupting or destroying our communications based on
information detected in the pattern or content of our transmissions. This is
accomplished by using the following RATELO procedures:
a. Reduce operator distinguishing characteristics. Many of our RATELOs
can be readily identified by certain voice characteristics or overused phrases.
The enemy can use these distinguishing characteristics to identify a unit even
though frequencies and call signs are changed periodically. Strictly adhering
to the proper use of procedure words (PROWORDs) as outlined in FM 24-18 helps
us to keep operator distinguishing characteristics to a minimum. However, this
is not enough. Accents and overused phrases must also be kept to a minimum. The
enemy must not be able to associate a particular RATELO with a particular unit.
b. Operate on a random schedule. As stated before, the enemy can gather
information based on the pattern as well as the content of our radio
communications. Therefore, we must not develop patterns through hourly radio
checks, daily reports at specific times, or any other periodic transmission.
Periodic reports should be made by alternate means of communications. We must
take all reasonable measures to deny information to enemy intelligence
analysts. Operating on a random schedule is one example.
c. Authenticate.
(1) Proper use of authentication prevents the enemy from deceptively
entering our nets. It is a procedure that must be used in radio systems that do
not use speech secure devices. The enemy has skilled experts whose sole mission
is to enter our nets by imitating friendly radio stations. This threat to our
radio communications can be minimized by the proper use of authentication.

2-6
 FM 24-33

Procedures for authentication are found in the supplemental instructions to the

SOI. Authentication is required in the following situations:
(a) You suspect the enemy is on your net.
(b) You are challenged by someone to authenticate. (Do not break radio
listening silence to do this.)
(c) You transmit directions or orders that affect the tactical
situation, such as change locations, shift fire, or change frequencies.
(d) You talk about enemy contact, give an early warning report, or issue
a follow-up report. (This rule applies even if you used a brevity list or
operations code.)
(e) You tell a station to go to radio or listening silence or ask it to
break that silence. (Use transmission authentication for this.)
(f) You transmit to a station that is under radio listening silence.
(Use transmission authentication for this.)
(g) You cancel a message by radio or visual means, and the other station
cannot recognize you.
(h) You resume transmitting after a long period of time, or it is the
first transmission.
(i) You are authorized to transmit a classified message in the clear.
(Use transmission authentication for this.)
(j) You are forced, because of no response by a called station, to send
a message in the blind. (Use transmission authentication for this.)
(2) All instances in which the enemy attempts to deceptively enter our
nets to insert false information must be reported. The procedures for reporting
these incidents are in Chapter 4. The procedures are also in the supplemental
instructions to the SOI.
d. Encrypt all essential elements of friendly information. EEFI are
those items of information which we must not allow the enemy to obtain. A
broad, general list of these items of information is contained in the
supplemental instructions to the SOI. These items of EEFI are applicable to
most Army units engaged in training exercises or tactical operations. The list
is to support the Army self-monitoring program and is not all inclusive.
Individual units should develop a more specific EEFI list to be included in
unit operation orders, operation plans, and field SOPs. These items of
information must be encrypted manually or electronically before transmission.
Electronic encryption is accomplished by using COMSEC devices such as the
KY-57/58, KG-84, or KG-93/94. Manual encryption is accomplished by using

2-7
FM 24-33

approved operations codes. Manual and electronic encryption need not be used
together. Either method used alone will protect EEFI from enemy exploitation.
2-5. Equipment and Communications Enhancements
In addition to the equipment enhancements and proper RATELO procedures,
other techniques can be used to reduce the vulnerability of friendly
communications to hostile exploitations. Some of these ECCM procedures are
the introduction of frequency hopping modules in radios, null steering and
adaptive antennas, spread spectrum waveforms, automatic adjustable power
output, and fiber optics technology.
a. Frequency hopping is particularly useful in lessening the effects of
enemy communications jamming and in denying the enemy friendly position
location data. This is done by changing the instantaneous frequency of a
narrowband transmission in a psuedo-random manner. The new family of SINCGARS
will employ frequency hopping.
b. Null steering and adaptive antenna techniques are designed to
achieve more survivable communications systems. Null steering masks the
radiation pattern to nullify the effects of jamming and provides an improved
signal-to-jamming ratio. These techniques are typically coupled with spread
spectrum waveforms combining frequency hopping with psuedo-noise coding.
c. Spread spectrum techniques are intended to suppress interference by
other users (hostile or friendly), to provide multiple access (user sharing), ..
and to eliminate multipath interference (self-jamming caused by a delayed
signal). The transmitted intelligence is deliberately spread across a very wide
frequency band in the operating spectrum so that it becomes hard to detect from
normal noise levels. The Enhanced Position Location Reporting System (EPLRS)
and the Joint Tactical Information Distribution System (JTIDS) use this
technique.
d. Adjustable power automatically limits the radiated power to a level
sufficient for effective communications, thereby reducing the electronic
signature of the subscriber. The radios currently planned for use in the Mobile
Subscriber Equipment (MSE), such as the radio access units (RAUs) and the
mobile subscriber radiotelephone terminals (MSRTs), use this feature.
e. Frequency hopping multiplexer (FHMUX) and high-power broadband
vehicular whip antennas (HPBVWA) are currently being developed. The FHMUX is
an antenna multiplexer used with SINCGARS in both stationary and mobile
operations. This multiplexer will allow up to five SINCGARS to transmit and
receive through one VHF-FM broadband antenna (OE-254 or HPBVWA) while operating
in frequency hopping mode, nonhopping mode, or a combination of both. It will
also be capable of operating with the current VRC-12 family of radios. Visual
and electronic profiles of command posts will be reduced by using one antenna
instead of up to five. Also, emplacement and displacement times will be greatly
reduced.

2-8
 FM 24-33

Chapter 3
Remedial Electronic Counter-Countermeasures
Techniques

3-1. Introduction
Remedial ECCM techniques (Table 3-1) reduce the effectiveness of enemy
efforts to jam our radio nets. They apply only to enemy jamming efforts or any
unidentified or unintentional interference that disrupts our ability to
communicate. There are no remedial ECCM techniques that apply to other actions
the enemy might use to disrupt or destroy our communications. We must prevent
enemy jamming and interference-- after the enemy has gathered information about
us , we cannot get it back.

3-1
FM 24-33

3-2. Types of Jamming Signals

Jamming is an effective way for the enemy to disrupt our command,
control, and communications on the battlefield. All the enemy needs to jam us
is a transmitter tuned to our frequency with enough power to override friendly
signals at our receivers. Jammers operate against receivers--not transmitters.
There are two modes of jamming: spot and barrage. Spot jamming is concentrated
power directed toward one channel or frequency. Barrage jamming is power
spread over several frequencies or channels at the same time. Jamming can be
difficult, if not impossible to detect. For this reason, we must always be
aware of the possibility of jamming and be able to recognize it. The two types
of jamming most commonly encountered are obvious and subtle jamming.
a. Obvious jamming. This is normally very simple to detect. The more
commonly used jamming signals of this type are described below. Do not try to
memorize them; just be aware that these and others exist. When experiencing a
jamming incident, it is more important to recognize and overcome the incident
than to identify it formally.
(1) Random noise. This is synthetic radio noise. It is random in
amplitude and frequency. It is similar to normal background noise and can be
used to degrade all types of signals. Operators often mistake it for receiver
or atmospheric noise and fail to take appropriate ECCM actions.
(2) Stepped tones. These are tones transmitted in increasing and
decreasing pitch. They resemble the sound of bagpipes. Stepped tones are
normally used against single-channel AM or FM voice circuits.
(3) Spark. The spark signal is easily produced and is one of the most
effective for jamming. Bursts are of short duration and high intensity. They
are repeated at a rapid rate. This signal is effective in disrupting all types
of radio communications.
(4) Gulls. The gull signal is generated by a quick rise and slow fall of
a variable radio frequency and is similar to the cry of a sea gull. It produces
a nuisance effect and is very effective against voice radio communications.
(5) Random pulse. In this type of interference, pulses of varying
amplitude, duration, and rate are generated and transmitted. They are used to
disrupt teletypewriter, radar, and all types of data transmission systems.
(6) Wobbler. The wobbler signal is a single frequency which is modulated
by a low and slowly varying tone. The result is a howling sound that causes a
nuisance effect on voice radio communications.
(7) Recorded sounds. Any audible sound , especially of a variable nature,
can be used to distract radio operators and disrupt communications. Music,
screams, applause , whistles, machinery noise, and laughter are examples.

3-2
 FM 24-33

(8) Preamble jamming. This type of jamming occurs when a tone resembling
the synchronization preamble of the speech security equipment is broadcast over
the operating frequency of secure radio sets. Preamble jamming results in all
radios being locked in the receive mode. It is especially effective when
employed against radio nets using speech security devices.
b. Subtle jamming. Subtle jamming is not obvious; no sound is heard
from our receivers. They cannot receive an incoming friendly signal, even
though everything appears normal to the radio operator. Subtle jamming takes
advantage of design features of the AN/PRC-77 and AN/VRC-12 series radios. In
order to activate the receiver of an AN/PRC-77 in the SQUELCH mode or an
AN/VRC-12 series radio in the NEW SQUELCH ON mode, a 150-hertz tone must be
transmitted to them along with the carrier signal. In addition to this squelch
feature, the AN/PRC-77 and AN/VRC-12 series radio receivers lock onto the
strongest carrier signal received and eliminate the reception. of all other
signals. For example, if we have an AN/PRC-77 in the SQUELCH mode and an
AN/VRC-12 series radio in the NEW SQUELCH ON mode and they receive a jamming
signal without the 150-hertz tone, the receivers of these radios will not be
activated by any signal as long as the jamming signal is stronger than any
other signal being received. In effect, the threat jammers block out these
radios' ability to receive a friendly transmission without the operator being
aware it is happening. This is called squelch capture and is a subtle jamming
technique. The radio operator can readily detect jamming in all other function
control modes and the other modes must be checked. Often, we assume that our
radios are malfunctioning instead of recognizing subtle jamming for what it is.
3-3. Recognizing Jamming
a. Radio operators must be able to recognize jamming. Again, this is
not always an easy task. Threat jammers may employ obvious or subtle jamming
techniques. Also, interference may be caused by sources having nothing to do
with enemy jamming. Interference may be caused by the following:
Unintentionally by other radios (friendly and enemy).
Other electronic or electric/electromechanical equipment.
Atmospheric conditions.
Malfunction of the radio.
A combination of any of the above.
(1) Internal or external interference. The two sources of interference
are internal and external. If the interference or suspected jamming can be
eliminated or substantially reduced by grounding the radio equipment or
disconnecting the receiver antenna, the source of the disturbance is most
likely external to the radio. If the interference or suspected jamming remains
after grounding or disconnecting the antenna, the disturbance is most likely

3-3
FM 24-33

internal and is caused by a malfunction of the radio. Maintenance personnel

should be contacted to repair it. External interference must be checked further
for enemy jamming or unintentional interference.
(2) Jamming or unintentional interference. Unintentional interference
may be caused by other radios, some other type of electronic or electric/
electromechanical equipment, or atmospheric conditions. The battlefield is so
crowded with radios and other electronic equipment that some unintentional
interference is virtually unavoidable. Also, the static electricity produced by
atmospheric conditions can negatively affect radio communications.
Unintentional interference normally travels only a short distance, and a search
of the immediate area may reveal the source of this type of interference.
Moving the receiving antenna for short distances may cause noticeable
variations in the strength of the interfering signal. These variations normally
indicate unintentional interference. Conversely, little or no variation
normally indicates enemy jamming. Regardless of the source, actions must be
taken to reduce the effect of interference on our communications.
b. In all cases, suspected enemy jamming and any unidentified or
unintentional interference that disrupts our ability to communicate must be
reported. This applies even if the radio operator is able to overcome the
effects of the jamming or interference. The format for reporting this
information is the MIJI report. Instructions for submitting a MIJI report are
in Chapter 4 and are usually listed in the SOI. As it applies to remedial ECCM
techniques, the information provided to higher headquarters in the MIJI report
can be used to destroy the enemy jamming efforts or take other action to our
benefit.
c. The enemy can use two types of jamming signals: powerful unmodulated
or noise-modulated signals. Unmodulated jamming signals are characterized by a
lack of noise. Noise-modulated jamming signals are characterized by obvious
interference noises. The following procedures will help radio operators
determine whether their radios are being threatened by enemy jamming.
(1) AN/PRC-77.
(a) Turn the function control from the SQUELCH OFF to the ON position.
(b) Lack of noise may indicate that the radio is being jammed by an
unmodulated jamming signal. The operator should temporarily disconnect the
antenna. If normal static noise returns when the antenna is disconnected, there
is a high probability that the radio is being jammed by an unmodulated signal.
(c) A greater than normal level of noise or an obviously modulated
signal may indicate that the radio is being jammed by a noise-modulated jamming
signal. The operator should temporarily disconnect the antenna. If normal
static noise returns when the antenna is disconnected, the radio most likely is
being jammed by a noise-modulated signal.

3-4
 FM 24-33

(d) If the above tests indicate there is a high probability the radio is
being jammed, the operator should follow the local SOP to reestablish
communications and initiate a MIJI report informing higher headquarters of the
incident.
(2) AN/VRC-12 series radio.
(a) Turn the squelch control from the NEW SQUELCH ON to the NEW SQUELCH
OFF mode.
(b) Lack of noise and an unlighted call light may indicate that the
radio is being jammed by an unmodulated jamming signal. The operator should
temporarily disconnect the antenna. If normal static noise returns and the call
light goes off when the antenna is disconnected, the radio is most likely being
jammed by an unmodulated signal.
(c) A greater than normal level of noise or an obviously modulated
signal may indicate that the radio is being jammed by a noise-modulated jamming
signal. The operator should temporarily disconnect the antenna. If normal
static noise returns, and the call light goes off when the antenna is
disconnected, there is a high probability that the radio is being jammed by a
noise-modulated signal.
(d) If the above tests indicate that there is a high probability that
the radio is being jammed, the operator should follow the local SOP to
reestablish communications and initiate a MIJI report informing higher
headquarters of the incident.
(3) Other unique organizational radios. Signal officers should
coordinate with organic military intelligence units for assistance in
developing appropriate tests for special capacity radios or radios that are
unique to that specific organization. Examples of these are nonstandard issue,
off-the-shelf commercial, intermediate high frequency radios (IHFR), or
SINCGARS radios. Signal officers should ensure that their unit radio
operators are trained to use these radios.
3-4. Overcoming Jamming
The enemy constantly strives to perfect and use new and more confusing
forms of jamming. Our radio operators must be increasingly alert to the
possibility of jamming. Training and experience are the most important tools
operators have to determine when a particular signal is a jamming signal.
Exposure to the effects of jamming in training or actual situations is
invaluable. The ability to recognize jamming is important, because jamming is a
problem that requires action. Once it is determined that jamming is being used
against our radios, the following actions must be taken. If any of the actions
taken alleviate the jamming problem, we simply continue normal operations and
make a MIJI report to higher headquarters.
a. Continue to operate. Stop for a moment and consider what the enemy
is doing during his typical jamming operation. Usually, enemy jamming involves

3-5
FM 24-33

a period of jamming followed by a brief listening period. He is attempting to

determine how effective his jamming has been. What we are doing during this
short period of time when he is listening will tell him how effective his
jamming has been. If the operation is continuing in a normal manner, as it was
before the jamming began, the enemy will assume that his jamming has not been
particularly effective. On the other hand, if he finds us excitedly discussing
our problem on the air or if we have shut down our operation entirely, the
enemy may very well assume that his jamming has been effective. Because the
enemy jammer is monitoring our operation this way, we have a simple yet very
important rule that applies when we are experiencing jamming. Unless
otherwise ordered, never shut down operations or in any other way disclose
to the enemy that you are being adversely affected. This means normal
operations should continue even when degraded by jamming.

b. Improve the signal-to-jamming ratio. The signal-to-jamming ratio is

the relative strength of the desired signal to the jamming signal at the
receiver. Signal refers to the signal we are trying to receive. Jamming refers
to the hostile or unidentified interference being received. It is always best
to have a signal-to-jamming ratio in which the desired signal is stronger than
the jamming signal. In this situation, the desired signal cannot be
significantly degraded by the jamming signal. The following will improve the
signal-to-jamming ratio to our benefit.
(1) Adjust the receiver. When jamming is experienced, we should always
check to ensure the receiver is tuned as precisely as possible to the desired
incoming signal. A slight readjustment of the receiver may provide an improved
signal-to-jamming ratio. Specific methods that apply to a particular radio set
are explained in the appropriate operator’s manual. Depending on the radio
being used, some of these methods are--
Adjust the beat frequency oscillator (BFO).
Adjust the bandwidth.
Adjust the gain or volume control.
Fine tune the frequency.
(2) Increase the transmitter power output. The most obvious way to
improve the signal-to-jamming ratio is to increase the power output of the
transmitter emitting the desired signal. In order to increase the power output
at the time of jamming, the transmitter must be set on something less than full
power when jamming begins. We must remember that using low power as a
preventive ECCM technique depends on the enemy not being able to detect our
radio transmissions. Once the enemy begins jamming our radios, the threat of
being detected becomes academic. We should use the reserve power on our
terrestrial line-of-sight radios to override the enemy’s jamming signal.
Tactical satellite communications terminals will not increase their transmit
power.

3-6
 FM 24-33

(3) Adjust or change the antenna. Antenna adjustments can appreciably

improve the signal-to-jamming ratio. When jamming is experienced, the radio
operator should ensure the antenna is optimally adjusted to receive the desired
incoming signal. Specific methods that apply to a particular radio set are in
the appropriate operator’s manual. Depending on the antenna being used, some of
these methods are--

Reorient the antenna.

Change the antenna polarization. (Must be done by all stations.)
Install an antenna with a longer range.
(4) Establish a retransmission station. A retransmission station can
increase the range and power of a signal between two or more radio stations.
Depending on the available resources and the situation, this may be a viable
method to improve the signal-to-jamming ratio.

(5) Relocate the antenna. Frequently, the signal-to-jamming ratio may be

improved by relocating the antenna and associated radio set affected by the
jamming or unidentified interference. This may mean moving a few meters or
several hundred meters. It is best to relocate the antenna and associated radio
set so that there is a terrain feature between them and any suspected enemy
jamming location.
c. Use an alternate route for communications. In some instances, enemy
jamming will prevent us from communicating with a radio station with which we
must communicate. If radio communications have been degraded between two radio
stations that must communicate, there may be another radio station or route of
communications that can communicate with both of the radio stations. That radio
station or route should be used as a relay between the two other radio
stations.
d. Change frequencies. If a communications net cannot overcome enemy
jamming using the above measures, the commander (or designated representative)
may direct the net to be switched to an alternate or spare frequency. If
practical, dummy stations can continue to operate on the frequency being jammed
to mask the change to an alternate frequency. This action must be preplanned
and well coordinated. During enemy jamming, it is very difficult to coordinate
a change of frequency. All radio operators should know when and under what
circumstances they are to switch to an alternate or spare frequency. If this is
not done smoothly, the enemy may discover what is happening and try to degrade
our communications on the new frequency.
e. Acquire another satellite. In many cases, a satellite communications
terminal can see more than one satellite in a given theater. If one satellite
is being jammed, then the operator should request permission to access another
satellite until the jamming ceases or until the enemy jammer is neutralized.

3-7
 FM 24-33

Chapter 4
Meaconing, Intrusion, Jamming, and Interference
Reporting

4-1. Introduction
a. Meaconing, intrusion, and jamming are deliberate actions intended to
deny an enemy the effective use of the electromagnetic spectrum. Interference
is the unintentional disruption of the effective use of the electromagnetic
spectrum by friendly, enemy, or atmospheric sources. Collectively, meaconing,
intrusion, jamming, and interference incidents are referred to as MIJI
incidents.
b. MIJI reports document all disruptions of--
Radios.
Radars.
Navigational aids (NAVAIDS).
Satellites.
Electro-optics.
Disruptions caused by equipment malfunctions or destruction are exceptions. The
MIJI report serves two purposes. First, it provides information to the tactical
commander allowing timely decisions to be made to overcome the MIJI problem.
Second, it provides a historical record of MIJI incidents from which
appropriate ECCM techniques and measures can be developed. This helps us to
counter future attempts by the enemy to deny us the effective use of the
electromagnetic spectrum.
c. This chapter gives instructions for completing MIJI reports for
communications and noncommunications emitters. To fulfill the two purposes
stated above, there are two kinds of MIJI reports. The MIJIFEEDER voice
template message is a brief report of a MIJI incident. It serves as a
decision-making tool for the command. The MIJIFEEDER record message is a
complete report of a MIJI incident. This provides a historical record from
which appropriate ECCM techniques and measures can be developed. DA Pam 25-7
gives instructions for completing the MIJI reports.

4-1
FM 24-33

4-2. Terms
a. Meaconing. Meaconing is a system of receiving radio beacon signals
from NAVAIDs and rebroadcasting them on the same frequency to confuse
navigation. The enemy conducts meaconing operations against us to prevent our
aircraft and ships from arriving at their intended targets or destinations.
Successful enemy meaconing causes--
Aircraft to be lured into hot landing zones or enemy airspace.
Ships to be diverted from their intended routes.
Bombers to expend ordnance on false targets.
Ground stations to receive inaccurate bearings or position locations.
b. Intrusion. Intrusion is intentionally inserting electromagnetic
energy into transmission paths in any manner. The object is to deceive
equipment operators or cause confusion. The enemy conducts intrusion operations
against us by inserting false information into our receiver paths. This false
information may consist of voice instructions, ghost targets, coordinates for
fire missions, or even rebroadcasting of prerecorded data transmissions.
c. Jamming. Jamming is deliberately radiating, reradiating, or
reflecting electromagnetic energy to impair the use of electronic devices,
equipment, or systems. The enemy conducts jamming operations against us to
prevent us from effectively employing our radios, radars, NAVAIDs, satellites,
and electro-optics.
d. Interference. Interference is any electrical disturbance that causes
undesirable responses in electronic equipment. As a MIJI term, interference
refers to the unintentional disruption of the use of radios, radars, NAVAIDs,
satellites , and electro-optics. This interference may be of friendly, enemy, or
atmospheric origin. For example, a civilian radio broadcast may interfere with
military communications.
4-3. MIJIFEEDER Voice Template
a. Purpose and use. The MIJIFEEDER voice template has only the
information needed to adequately inform the tactical commander of the incident
in a timely manner. It is used to make evaluation of enemy actions or
intentions easier and to provide data to implement appropriate counter-
countermeasures.
b. Reporting procedure.
(1) The MIJIFEEDER voice template is forwarded through the chain of
command to the unit operations center by the equipment operator experiencing
the MIJI incident. The report should be forwarded using the most expeditious
secure communications means available.

4-2
 FM 24-33

(2) Upon receiving the MIJIFEEDER voice template, the signal officer--
(a) Coordinates the unit response to the MIJI incident with the unit
operations officer, intelligence officer, fire support officer, and unit
commander(s), as applicable and appropriate.
(b) Consolidates the voice templates referring to the same MIJI
incident.
(c) Forwards one MIJIFEEDER voice template report for each MIJI incident
through operations channels to the corps operations center or as appropriate.
This report should be accompanied by any requests for support the command needs
to overcome the MIJI problem.
(d) Initiates staff action to complete the MIJIFEEDER record message as
quickly as possible. (Coordination will not delay reporting the incident within
24 hours.)
(3) Upon receiving the MIJIFEEDER voice template, in the process of
forwarding it through operations channels, the signal officer at each
operations center takes the following actions:
(a) Provides support as requested by the unit submitting the voice
template report, if possible and deemed appropriate by the command.
(b) Informs the operations officer and intelligence officer of the
details of the MIJI incident.
c. Report format and contents. The MIJIFEEDER voice template has been
developed for use under the JINTACCS program. It is designed to ensure
interoperability on the battlefield during combined, joint, and intra-Army
operations. The standardized, simple format permits the expeditious
notification of appropriate action elements in time-critical situations. Only
the completed and underlined areas (as appropriate) of the format are
transmitted. As shown in Figure 4-1, MIJIFEEDER voice templates are self-
explanatory and contain ten items of information. When the message is
transmitted over nonsecure means , each line number is stated and the completed
information must be encrypted. When a secure means is used, the title of each
line is transmitted along with the completed information. The operator of the
affected system fills out the MIJIFEEDER voice template as shown below.
Line 1 - Enter the unit designation.
Line 2 - Enter the type of interference encountered:
Meaconing
Jamming
Intrusion
Interference
Chaff

4-3
FM 24-33

Line 3 - Enter the unit location in either of two ways: Longitude

and latitude in minutes and seconds, or in complete grid coordinates down to 10
or 100 meter increments.
Line 4 - Enter 2 digits each for day, hour, minute, and 1 letter for
the time zone for the start of the MIJI incident.
Line 5 - Enter 2 digits each for day, hour, minute, and 1 letter for
the time zone for the end of the MIJI incident.
Line 6 - Enter the nomenclature for the equipment affected.
Line 7 - Enter the channel, frequency, or frequency range affected
and the unit of measure. Examples: 3456.2 kHz, 42.35 MHz, or 2.5 to 2.7 GHz.
Line 8 - Enter, in your own words, a brief description or other
information regarding the MIJI incident.
Line 9 - When required, enter the hour, minute, and time zone.
Line 10 - Enter the message authentication in accordance with the
joint task force (JTF) requirements.
Figure 4-2 is an example of a completed voice template. The circled numbers to
the right of each line in Figure 4-2 correspond to extracts of the MIJIFEEDER
record message format in Annex 81, DA Pam 25-7.

4-4
FM 24-33

4-5
FM 24-33

4-6
 FM 24-33

4-4. MIJIFEEDER Record Message Report

a. Purpose and use. The MIJIFEEDER record message is a complete report
of a MIJI incident. It provides a basis for developing appropriate
counteraction measures to be implemented at proper command levels. AR 105-3 and
DA Pam 25-7 establish the information to be included in this report. The Joint
Electronic Warfare Center (JEWC) is the action agency for this report. All
MIJIFEEDER record message reports initially evaluated as nonexercise should be
forwarded as soon as possible to the JEWC. The JEWC uses these reports to
develop trends and to evaluate foreign ECM operations. They are also used by
the JEWC to recommend operational methods and equipment changes that will
reduce MIJI vulnerability of our:
Radios.
Radars.
NAVAIDs.
Satellites.
Electro-optics.
b. Reporting procedures.
(1) The MIJIFEEDER record message is forwarded by the signal officer of
the affected unit to the JEWC SAN ANTONIO TX//OPM//through operations channels
to the corps operations center. All MIJIFEEDER reports are forwarded via secure
means within 24 hours of the MIJI incident.
(2) Items such as photographs, diagrams, and tape recordings, that
cannot be included in the message are forwarded by other means (for example, US
mail) to the JEWC/OPM, San Antonio, TX 78243-5000, as soon as possible.
(3) Each operations center receiving this report should check the
contents for information that may be of use to the entire command.
c. Report format and contents. Excerpts from a joint message form and
DA Pam 25-7 at Figure 4-3 illustrate the proper MIJIFEEDER record message
format. The circled numbers on the joint message form correspond with the
explanation in Annex 81, DA Pam 25-7. Entry lists 11, 97, and 98, referenced in
the explanation column, are Appendices A, B, and C of this manual.

4-7
FM 24-33

4-8
FM 24-33

4-9
FM 24-33

4-10
FM 24-33

4-11
FM 24-33

4-12
FM 24-33

4-13
FM 24-33

4-14
FM 24-33

4-15
FM 24-33

4-16
FM 24-33

4-17
FM 24-33

4-5. Meaconing, Intrusion, Jamming, and Interference Security Classification

Guide
Security classification of MIJI incidents or MIJI evaluation reports is
determined principally by intent and location of the implied or stated source
of the problem. Stations in combat areas or having a sensitive military mission
ordinarily classify all MIJI reports.
Information Revealing: Classification
a. The specific identification of an S; OADR
unfriendly platform or location by country or
coordinates as the source of meaconing, intrusion,
or jamming incident.
b. The term meaconing, intrusion, jamming and U
interference; the acronym MIJI; and that MIJI analysis
is a function of the JEWC.
c. That an organization submits MIJI incident U
reports.
d. Broadly stated objectives of the MIJI U
program, including explanation of each of the terms
that comprise the acronym MIJI.
e. Suspected meaconing, intrusion, or jamming, C; OADR
but sources cannot be identified.
f. Interference when source is clearly U
identified as US or friendly nation electromagnetic
emitters.

g. Interference to US or friendly country C; OADR

electromagnetic equipment caused by ECM exercise in
unfriendly nations.
h. Interference from unfriendly radio C; OADR
broadcast stations, meteorological stations, and
other such fixed stations.

4-18
 FM 24-33

i . Parametric data of classified US Classify

electromagnetic equipment. Refer to correspondence
classification guide for the equipment equal to the
affected. security
category
assigned to
the equipment
affected.

j. Specific or general susceptibility or S; OADR

vulnerability of US electronic system to foreign
exploitation.

4-19
 FM 24-33

Appendix A

Entry List 11
Location
There are several different ways of giving a location in JINTACCS messages.
This entry list shows you how to write locations in the following ways:
UTM coordinates
Abbreviated UTM coordinates
Latitude and longitude (Lat/Long)
Verified latitude and longitude
Geographic reference (GEOREF)
Bearing and range (meters)
Bearing and range (nautical miles)
Basic Encyclopedia number (BE number)
When you use this entry list make sure to use the section called for by the
Chapter 3 message instructions. Also make sure to write your location to the
accuracy called for by the message instructions.
UTM
Follow the directions below to enter UTM coordinates.
(l). Enter the grid zone designator in first 3 spaces (2 numbers, 1 letter).
(2) . Enter 100,000 meter grid square (2 letters).
(3) . The next spaces (up to 5) are for casting.
(4). The next spaces (up to 5) are for northing.

A-1
FM 24-33

NOTE : Make sure to write UTM coordinates to the accuracy required by Chapter 3
directions. If you do not have the location to the required accuracy put zeros
in the spaces for the unknown values. For example, if you must write
coordinates to the nearest 1 meter, but you only know them to the nearest 100
meters enter:

ABBREVIATED UTM
Enter abbreviated UTM coordinates by following the same steps as above for UTM
coordinates EXCEPT start with step 2. (Do not enter in the grid zone
designator.) You can write abbreviated UTM coordinates to the accuracies shown
in the examples below.

LAT/LONG
Follow the directions below to enter Latitude and Longitude coordinates.
(1). Enter latitude in degrees (00-90), minutes (00-59), seconds (00-59). If
message instructions call for it, you may enter minutes or seconds to
the nearest tenth (.1).
(2) . Enter N for North latitude or S for South latitude.
(3) . Enter longitude in degrees (000-180), minutes (00-59), seconds (00-59).
If a message instructions call for it, you may enter minutes or seconds
to the nearest tenth (.1).
(4) . Enter E for East latitude or W for West latitude.

NOTE: Make sure to write LAT/LONG coordinates to the accuracy required by

Chapter 3 directions. If you do not have the location to the required accuracy
put zeros in the spaces for the unknown values. For example, if you must write
coordinates to the nearest second, but you only know them to the nearest minute
enter:

A-2
 FM 24-33

VERIFIED LAT/LONG
Follow the directions below to enter verified Latitude and Longitude
coordinates.
(l). Enter latitude in degrees (00-90), minutes (00-59), and seconds (00-59).
(2). Enter N for North latitude or S for South latitude.
(3) . Enter the checksum digit for latitude (righthand digit of the sum of all
the digits in latitude).
(4) . Enter a hyphen (-).
(5). Enter longitude in degrees (000-180), minutes (00-59), and seconds
(00-59).
(6) . Enter E for East longitude or W for West longitude.
(7). Enter the checksum digit for longitude (righthand digit of the sum of
all the digits in longitude).

NOTE: Make sure to write verified LAT/LONG coordinates to the accuracy required
by Chapter 3 directions. If you do not have the location to the required
accuracy put zeros in the spaces for the unknown values. For example, if you
must write coordinates to the nearest second, but you only know them to the
nearest minute enter:

A-3
FM 24-33

GEOREF
Follow the directions below to enter GEOREF coordinates.
(l). Enter 2 letters for the 15-degree segment of the Earth defined by the
GEOREF system.
(2) . Enter 2 letters for the l-degree segment of the Earth defined by the
GEOREF system.
(3) . Enter 2 digits (00-59) to show the casting coordinate to the nearest
minute.
(4) . Enter 2 digits (00-99) to show the casting coordinate to the nearest
hundredth of a minute.
(5). Enter 2 digits (00-59) to show the northing coordinate to the nearest
minute.
(6). Enter 2 digits (00-99) to show the northing coordinate to the nearest
hundredth of a minute.

NOTE: Make sure to write GEOREF coordinates to the accuracy required by

Chapter 3 directions. If you do not have the location to the required accuracy
put zeros in the spaces for the unknown values. For example, if you must write
coordinates to the nearest minute, but you only know them to the nearest degree
enter:

A-4
 FM 24-33

BEARING AND RANGE (METERS)

NOTE: Use this method only in the MCMOPS and MINEOPS messages.
Follow the steps below to give location of one object by giving its direction
and distance in meters from another object.
(l). Enter direction (degree magnetic) in the first three spaces (000-359).
(2) . Enter a hyphen. Then enter the distance in meters. You can use up to
five spaces (l-99999).
(3) . Enter a hyphen. Then enter the name of the location you are measuring
from (city, town, terrain feature, call sign, reference point from an
operations order, etc.). You can use up to 12 spaces.
EXAMPLE: The following example shows an object located 500 meters from Hill
239 in a direction of 50 degrees magnetic:

NOTE: You can use bearing and range in meters to outline an area in set
"MINEFIELD" of the MINEOPS message or sets "MCMACT, MOA, and SAFELANE" of the
MCMOPS message. Use the repeatable field "location" as shown below:
(l). In the first field give the location of the first reference point. (Use
LAT/LONG, UTM, or location name.)
(2). In the next fields use bearing and range in meters to give the relative
location of each point from the point before it.
EXAMPLE: The example below shows an area where:
Point A is at 22° 15’ north latitude and 30° 9’ east longitude.
Point B is 5000 meters from the Point A in a direction of 45°
magnetic.
Point C is 3000 meters from Point B in a direction of 325° magnetic

(POINT A) (POINT B) (POINT C)

A-5
FM 24-33

BEARING AND RANGE (NAUTICAL MILES)

Follow the steps below to give the location of one object by giving its
direction and distance in nautical miles from another object.
(l). Enter 3 digits (000-359) to give the direction (degrees true for
maritime, degrees magnetic for all other) from one object to the other
object.
(2) . Enter a hyphen, Then enter up to 12 characters to give the location from
which you are measuring (city, town, terrain feature, call sign,
reference point from an operations order, etc.).
(3) . Enter a hyphen. Then enter up to 3 digits (0-999) to give a distance
(nautical miles) from one object to the other object.
EXAMPLE
The following example shows an object 25 nautical miles from Hill 123 on a
bearing of 75 degrees magnetic.

A-6
 FM 24-33

BASIC ENCYCLOPEDIA NUMBERS

There are several ways to write basic encyclopedia (BE) numbers. The tables on
the next two pages show you how to write each one. (Each of the columns labeled
A-H is for a different type BE number. Make sure to use the right table and
column for the message you are writing).
Some BE numbers are assigned by DIA. They are in the columns marked by an *. If
you have a DIA assigned BE number you don’t need to follow the instructions to
enter it. Just enter it as is. The instructions are just to help you read DIA
assigned numbers in messages you receive.
To enter BE numbers you originate in the field follow the instructions in the
proper column and table shown below.
Use Table I (any column) for:
IIR and RECCEXREP

Use Table II (any column) for:

AFU.MFN FM.CFF FP.FPO NUCWARN
AFU.MFR FM.FMC FP.FPT TACELINT
ATI.ATR FM.MTO FP.NUCSCD TARBUL
ATI.TIR FM.NCF INTREP TGTINFOREP
ATO.CONF FM.SUB MISREP
Use Table II, Column F for:
AIRSUPREQ ALLOREQ REQCONF SARSIT
ALORD JSARREQ REQSTATTASK SORTIEALOT

A-7
FM 24-33

A-8
FM 24-33

A-9
 FM 24-33

Appendix B

Entry List 97
Organization Type
ORGANIZATION TYPE CODE

Unknown UNK
Administrative ADMIN
Airborne Commando ABNCMDO
Airborne Infantry ABNINF
Air Cavalry AIRCAV
Air Defense Artillery AAA
Airmobile Infantry AMBLINF
Air-to-Air Missile AAM
Air-to-Surface Missile ASM
Amphibious Assault AMPHASLT
Amphibious Engineers AMPHENG
Amphibious Tank AMPHTK
Antiair Warfare AAW
Antiarmor Missile AARMMSL
Antisubmarine Warfare ASW
Armor ARMOR
Armored Cavalry ARMDCAV
Army Aviation ARMYAVN
Artillery Unit ARTY
Assault Engineers ASLTENG
Assault Landing ASLTLAND
Biological Ordnance BIO
Capable Unit
Bomber BMBR

Cavalry CAV
Chemical CHEM
Combat Engineers CMBTENG
Combat Service Support CMBTSPT
Combat Type Unknown CMBT
Combined Arms CMBARM
Commando CMDO
Composite Warfare CWC
Commander
Dismounted Cavalry DMTDCAV

B-1
FM 24-33

ORGANIZATION TYPE CODE

Electronic ECM
Countermeasures
Electronic Support ESM
Measures
Engineer ENG
EW Coordinator EWC

Field Artillery FLDARTY

Fighter FTR
Fighter Bomber FTRBMBR
Frog SSM Unit FROG
Gun-Howitzer HOWTZR
Helicopter HELO
Infantry INF
Infantry on Foot INFONFT
Intelligence INTEL
Maintenance MAINT
Marine Amphibious MAB
Brigade
Marine Amphibious MAF
Force
Marine Amphibious Unit MAU
Mechanized Infantry MECHINF
Medical MED
Military Police MP
Military School or SCH
Academy
Mining MINE
Mortar MORT
Motorized Rifle Troops MRFLTRP
Mountain Infantry MTINF
Navy Infantry/Marines
Nuclear Ordnance Capable NUC
Unit
Ordnance ORD
Paramilitary PARAMIL
Picket PKT
Pontoon PONT

B-2
 FM 24-33

ORGANIZATION TYPE CODE

Railroad Troops RRTRPS

Ranger RNGR
Reconnaissance RECON
Reconnaissance, Armor RCNARM

Sapper (Mine) SAP

Scud SSM Unit SCUD
Signal/Electronics SIGELECT
Special Forces SPFORCE
Supply SUPLY
Surface-to-Air Missile SAM
Surface-to-Surface SSM
Missile
Surveillance SUR

Tactical Air Control TACAIRC

Tactical Missiles TACMSLS
Tank TK
Light Tank LTK
Medium Tank MTK
Heavy Tank HTK
Tank Destroyer TKDSTR
Tank Recovery TKRCVY
Training TNG
Transport TRNSP
Transportation TRANSP

Weather WX

B-3
 FM 24-33

Appendix C

Entry List 98
Echelon Level
ECHELON LEVEL CODES

Unknown UNK

Army Army AIRARMY

Air Command AIRCMD
Air Control Party AIRCONP
Air Corps AIRCRPS
Air Detachment AIRDET
Air Division AIRDIV
Air Element AIRELMT
Air Flight AIRFLT
Air Group AIRGP
Air Regiment AIRRGT
Air Squadron AIRSQ
Air Wing AIRWG
Army Group ARMYGP

Battalion BN
Battery BTY
Border District BRDHQ
Headquarters
Brigade BDE

Combat Command CMBTCMD

Command CMD
Company CO
Corps CORPS

Detachment DET
Division DIV
Divisional Artillery DAG
Group
Field Army ARMY
Fleet F
Front FRNT

Group GP
Group of Forces GPFRCS
Group of Fronts GPFRNT

C-1
FM 24-33

ECHELON LEVEL CODES

Komendatura KMDTR
Major Fleet FLT

National Defense NDHQ

Headquarters
Naval Detachments NAVDET
Naval Division NAVDIV
Naval Force NAVFOR
Naval Group NAVGP
Naval Section NAVSEC
*Naval Task Element TE
*Naval Task Force TF
*Naval Task Group TG
Naval Squadron NAVSQ
*Naval Task Unit TU
Numbered Fleet NFLT

Otryad OTRYD

Patrol PTRL
Platoon PLT

Regiment RGT
Regimental Artillery RAG
Group
Section SEC
Squad SQD
Squadron SQ

Task Element TSKELMT

Task Force TSKFOR
Task Group TSKGP
Task Unit TSKUNIT
Theater Army THTA
Troop TROOP

Zastrova ZASTRV

*ONLY USE THESE ENTRIES IN SETS "NUID" AND "7SHPALRT"

C-2
 FM 24-33

Appendix D

Implementing Electronic Counter-Countermeasures

for Radio Systems
D-1. Background
a. It is assumed that your system has the proper received signal level
and that you and the other station are using low power; your sites are masked
from the enemy when possible by using terrain obstacles.
b. Systems that are parallel to the front lines are less open to ECM
than systems that are perpendicular. Division systems are more prone to ECM
than corps systems because of the proximity to front lines.
c. Multichannel systems should be separated from HF radios because of
the high power and resulting spontaneous and harmonic radiation. FM radios
should not be collocated with multichannel sets for the same reasons.
Collocated multichannel antennas should be either back to back or on-line to
reduce mutual interference. Antennas should never be in line with one another.
d. The need for dispersion and the need for high mobility always clash.
To mask a unit’s location, all radios including multichannel should be
separated from the command post by at least 2 kilometers (1.2 miles). Cables
should not be used to interconnect radios and the command post because cable
recovery is too time consuming. A radio link should be used when available.
e. In most cases, the enemy prefers to monitor our systems even though
they are denied clear reception of our signals because of encryption. An
electronic signature of our unit’s location is of better intelligence than
jamming. Multichannel systems indicate headquarters’ locations. Their presence
indicates a stable nonmobile situation. We give the enemy valuable signal
intelligence when stations go off the air and then reappear elsewhere. We are
telling the enemy our situation is changing.
f. Determining if ECM is being used against your system is not easy
since most interference is from our own emitters.

g. Proper and diligent frequency management is imperative. When

interference occurs, submit the MIJI report. Do not change the frequency up or
down to get away from interference. This creates additional problems for other
users. Use tactical satellite instead of terrestrial line of sight when
possible.

D-1
FM 24-33

D-2. Procedures
a. The following may indicate that your systems are being interfered
with either intentionally or unintentionally:
Subscribers report that trunks are noisy, or that the speech of the
other party is fuzzy or unintelligible.
Subscribers and switchboard operators report no contact with a
particular unit(s).
You are unable to make contact with the distant end on the
orderwire.
b. The following steps reduce or eliminate the effects of ECM or mutual
interference:
Checking equipment for proper alignment and frequency.
Increasing power if possible.
Checking antenna for correct azimuth and polarization.
Varying antenna height or relocating antenna.
Requesting a new frequency if the above fails to work.
Initiating a MIJI report.

D-2
 FM 24-33

Glossary
Abbreviations and Acronyms

AM amplitude modulated
AR Army regulation
ARTEP Army Training and Evaluation Program
attn attention
AUTOVON automatic voice network
BE basic encyclopedia
BFO beat frequency oscillator
bn battalion
c CONFIDENTIAL
CEOI communications-electronics operation instructions (see
SOI)
CEWI combat electronic warfare and intelligence
COMINT communications intelligence
COMSEC communications security
CPT captain
CW continuous wave
3
C command, control, and communications
3
C CM command, control, and communications countermeasures
DA Department of the Army
DF direction finder
ECCM electronic counter-countermeasures
ECM electronic countermeasures

Glossary-1
FM 24-33

E-O electro-optics
EEFI essential elements of friendly information
EPLRS Enhanced Position Location Reporting System
ESM electronic warfare support measures
EW electronic warfare
FHMUX frequency hopping multiplexer
FLOT forward line of own troops
FM frequency modulated/field manual (when used with a
number)
G2 Assistant Chief of Staff, G2 (Intelligence)
G3 Assistant Chief of Staff, G3 (Operations and Plans)
GEOREF geographic reference
GHz gigahertz
HF high frequency
hi high
HPBVWA high-power broadband vehicular whip antenna
HQ headquarters
IAW in accordance with
IED imitative electronic deception
inf infantry
IHFR intermediate high frequency radio
JEWC Joint Electronic Warfare Center
JINTACCS Joint Interoperability of Tactical Command and Control
Systems
JTF joint task force
JTIDS Joint Tactical Information Distribution System

Glossary-2
 FM 24-38

JUH-MTF Joint User Handbook for Message Text Format

kHz kilohertz
km kilometer
MED manipulative electronic deception
MHz megahertz
MIJI meaconing, intrusion, jamming, and interference
MSE Mobile Subscriber Equipment
MSRT mobile subscriber radiotelephone terminal
NAVAID navigational aid
NCS net control station
OADR Originating Agency Determination Required
OPCODE operations code
OPSEC operations security
pam pamphlet
PROWORD procedure word
pwr power
RATELO radiotelephone operator
RAu radio access unit
RDF radio direction finding
REC radio electronic combat
RWR radar warning receiver
s SECRET
S2 Intelligence Officer (US Army)
S3 Operations & Training Officer (US Army)
SED simulative electronic deception

Glossary-3
 FM 24-33

SIGINT signals intelligence

SINCGARS Single-Channel Ground and Airborne Radio System
SNAP-1 steerable null antenna processor
SOI signal operation instructions
SOP standing operating procedure
TRADOC United States Army Training and Doctrine Command
TX Texas
U unclassified
US United States
VHF very high frequency
Z Zulu

Terms
AUTHENTICATION. A security measure designed to protect a communications
system against acceptance of a fraudulent transmission or simulation by
establishing the validity of a transmission, message, or originator.
BREVITY CODE. A code which provides no security but which has as its
sole purpose the shortening of messages rather than the concealment of their
content.
COMMUNICATIONS-ELECTRONICS OPERATION INSTRUCTIONS (CEOI). (See signal
operation instructions.)
COMMUNICATIONS INTELLIGENCE (COMINT). Intelligence and technical
information derived from foreign communications by other than the intended
recipients.
COMMUNICATIONS SECURITY (COMSEC). The protection resulting from all
measures designed to deny unauthorized persons information of value which
might be derived from the possession and study of telecommunications, or to
mislead unauthorized persons in their interpretation of the results of such
possession and study.

Glossary-4
 FM 24-83

DECEPTION. Those measures designed to mislead the enemy by

manipulation, distortion, or falsification of evidence in order to induce him
to react in a manner prejudicial to his interests.
ELECTROMAGNETIC SPECTRUM. The frequencies present in a given
electromagnetic radiation. A particular spectrum could include a single
frequency or a wide range of frequencies.
ELECTRONIC COUNTER-COUNTERMEASURES (ECCM). That major subdivision of
electronic warfare involving actions taken to retain friendly effective use of
the electromagnetic spectrum.
ELECTRONIC COUNTERMEASURES (ECM). That division of electronic warfare
involving actions taken to prevent or reduce an enemy’s effective use of the
electromagnetic spectrum.
ELECTRONIC WARFARE (EW). Military action involving the use of
electromagnetic energy to determine, exploit, reduce, or prevent hostile use
of the electromagnetic spectrum and action which retains friendly use of the
electromagnetic spectrum. Electronic warfare is divided into three categories
- ESM, ECM, ECCM.
ELECTRONIC WARFARE SUPPORT MEASURES (ESM). That division of electronic
warfare involving actions taken under the direct control of an operational
commander to search for, intercept, locate, and identify sources of radiated
electromagnetic energy for the purpose of immediate threat recognition.
EMISSION CONTROL. The management of the use of the electromagnetic
spectrum by our forces.
ENCRYPT. To convert plain text into unintelligible form by means of a
cryptosystem. This cryptosystem can be manual or electronic.
ESSENTIAL ELEMENTS OF FRIENDLY INFORMATION (EEFI). Items or activities
associated with friendly planning which, if exposed to hostile intelligence
activities, would serve as intelligence indicators and thus tend to compromise
friendly intentions.
GUARDED FREQUENCIES. Frequencies restricted from friendly use or
jamming operations, Guarded frequencies are the enemy’s communications and
electronics systems from which signals intelligence (SIGINT) and ESM
information of tactical and technical importance is derived.
INTERCEPTION. As used in this manual, the act of listening to and/or
recording signals intended for another party for the purpose of obtaining
intelligence,
INTERFERENCE. Any electrical disturbance which causes undesirable
responses in electronic equipment.

Glossary-5
 FM 24-33

INTRUSION. The intentional insertion of electromagnetic energy into

transmission paths in any manner with the objective of deceiving operators or
of causing confusion.
JAMMING. The deliberate radiation, reradiation, or reflection of
electromagnetic energy with the object of impairing the use of electronic
devices, equipment, or systems being used by an enemy.
JOINT INTEROPERABILITY OF TACTICAL COMMAND AND CONTROL SYSTEMS
(JINTACCS). A program which provides for information exchange on the
battlefield among the military services, the Defense Intelligence Agency, and
the National Security Agency. It uses standardized message formats, rules, and
vocabulary. (Reference DA Pam 25-7.)
MEACONING. The transmission or retransmission of actual or simulated
navigation signals to confuse navigation. Meaconing stations cause inaccurate
bearings to be obtained by aircraft or ground stations.
NET CONTROL STATION (NCS). A station designated to control traffic and
enforce circuit discipline within a given net.
OPERATIONS CODE (OPCODE). A code used to encrypt tactical information.
OPERATIONS SECURITY (OPSEC). The process of denying adversaries
information about friendly capabilities and intentions by identifying,
controlling, and protecting indicators associated with planning and conducting
military operations and other activities.
OPERATIONS SECURITY INDICATORS. Actions or information , classified or
unclassified, obtainable by an adversary that would result in adversary
appreciations, plans, and actions harmful to achieving friendly intentions and
preserving friendly military capabilities.
PREVENTIVE ECCM TECHNIQUES. Those measures taken to reduce the
vulnerability of the friendly use of the electromagnetic spectrum to the
efforts by the enemy to disrupt or destroy that use.
PROCEDURE WORD (PROWORD). A word or phrase limited to radio telephone
procedure used to facilitate communications by conveying information in a
condensed standard form. (Reference ACP 125. )
PROTECTED FREQUENCIES. Frequencies used by tactical friendly forces for
a particular operational requirement that are restricted from friendly jamming
operations.
RADIO LISTENING SILENCE. A period during which all or certain radio
equipment is kept in a receive only mode on a given net except for the net
control station.

Glossary-6
 FM 24-33

RADIO SILENCE. A period during which all or certain radio equipment

capable of radiation is kept inoperative.
REMEDIAL ECCM TECHNIQUES. Those actions taken to reduce or negate the
effectiveness of enemy efforts to jam the friendly use of the electromagnetic
spectrum.
SIGNAL OPERATION INSTRUCTIONS (SOI). A series of orders issued for the
technical control and coordination of the signal activities of a command.
Contains frequencies, call signs, and other information used to establish and
maintain radio and other forms of communication.
SIGNAL-TO-JAMMING RATIO. The ratio at a selected point in a signal of
the strength of a desired signal to that of a jamming signal.

SINGLE-CHANNEL GROUND AND AIRBORNE RADIO SYSTEM (SINCGARS). A new

family of VHF-FM radios designed to provide the primary means of command and
control for Infantry, Armor, and Artillery units. The radios can transmit and
receive voice and tactical data while operating in a frequency hopping mode.

TABOO FREQUENCIES. Frequencies that are restricted from use or jamming

by friendly forces. The following are some examples of these frequencies.
Defense Communications System radar frequencies used for friendly early
warning air defense; internationally controlled or treaty-governed
frequencies, such as broadcast emergency frequencies and commercial air and
shipping traffic control frequencies.
VOICE TEMPLATES. Standardized pre-formatted messages used with the
JINTACCS message text procedures.

.
Glossary-7
 FM 24-33

References

Required Publications

Required publications are sources that users must read in order to

understand or to comply with this publication.
Allied Communications Publications (ACP)
125( ) Communication Instructions - Radiotelephone
Procedures
131( ) Communication Instructions - Operating Signals
Army Regulations (AR)
105-2 (C) Electronic Counter-Countermeasures
(ECCM)--Electronic Warfare Susceptibility and
Vulnerability (U)
105-3 Reporting Meaconing, Intrusion, Jamming
and Interference of Electromagnetic Systems
105-7 Quick Reaction Capability (QRC) for
Electronic Warfare
525-20 Command, Control and Communications
3
Countermeasures (C CM) Policy
525-22 (S) Electronic Warfare (EW) Policy (U)
530-1 Operations Security (OPSEC)
530-2 Communications Security
530-3 (C) Electronic Security (U)
Department of the Army Pamphlets (DA Pam)
25-7 Joint User Handbook for Message Text
Formats (JUH-MTF)
380-2 (C) SIGSEC: Defense Against SIGINT (U)
Field Manuals (FM)
24-1 Combat Communications
24-18 Tactical Single-Channel Radio
Communications Techniques
24-35 (0) Communications-Electronics
Operation Instructions (The CEOI)
25-100 Training the Force
34-1 Intelligence and Electronic Warfare Operations
34-40 (S) Electronic Warfare Operations (U)
34-62 Counter-Signals Intelligence (C-SIGINT)
Operations

References-1
FM 24-33

Forms
DA Form 2028 Recommended Changes to Publications and Blank Forms

Related Publications

Related publications are sources of additional information. They are

not required in order to understand this publication.
Allied Communications Publications (AC)
124( ) Communication Instructions - Radiotelegraph
Procedures
124 (C) US Supplement to ACP 124( ) (U)
126( ) *(R) Communication Instructions - Teletypewriter
(Teleprinter) Procedures (U)
Army Regulations (AR)
380-40 (C) Policy for Safeguarding and
Controlling COMSEC Information (U)
Field Manuals (FM)
34-86 Direction Finding Operations
100-2-1 Soviet Army Operations and Tactics
100-5 Operations
101-5 Staff Organization and Operations

Projected Publications
Projected publications are sources of additional information that
are scheduled for printing but are not yet available. Upon print, they will
be distributed automatically via pinpoint distribution. They may not be
obtained from the USA AG Publications Center until indexed in DA Pamphlet
25-30.
Field Manual (FM)
24-35 (0) Signal Operation Instructions
“The SOI”

*Allied Restricted

References-2
 FM 24-33

Index

Index-1
FM 24-33

Index-2
FM 24-33

Index-3
 FM 24-33

17 JULY 1990

By Order of the Secretary of the Army:

CARL E. VUONO
General, United States Army
Chief of Staff

Official:

WILLIAM J. MEEHAN, II
Brigadier General, United States Army
The Adjutant General

DISTRIBUTION:

Active Army, ARNG, and USAR: To be distributed in accordance with

DA Form 12-11-E, requirements for FM 24-33, Communications Techniques:
Electronic Counter-Countermeasures (Qty rqr block no. 1075).

* U.S. GOVERNMENT PRINTING 0FFICE:1994-300-769/22213 PIN: 049992-000