Communication Techniques in a Jungle Environment
Rapid, reliable communications are essential in jungle operations. Command, control, fire support, resupply, and evacuation are all dependent on effective communications. The importance of establishing and maintaining reliable communications cannot be overemphasized. For this reason, a commander must give communications high priority in his planning and supervision.
Jungle operations place additional demands on the resources of communications units and personnel. Tactical and signal units may require augmentation of signal personnel and equipment to accomplish the command and control functions. Besides providing normal tactical communications networks, signal units may have to operate long distance radio sets. Army aircraft will have to be used in many instances to provide a radio relay capability as well as to assist wire-laying operations.
TACTICAL COMMUNICATIONS MEANS
With the range of FM communications in a jungle environment significantly reduced due to the dense undergrowth, heavy rains, and hilly terrain, all means of communications should be used in a manner that complements one another. For all operations, backup means of communications must be planned. The common means of communication available are visual, sound, messenger, wire, and radio.
II. Communicating in the Jungle
Such means as arm-and-hand signals, pyrotechnics, flashlights, headlights, smoke grenades, mirrors, and panels normally allow quick transmission of messages and instructions. However, visual means of communication in the jungle are restricted by the dense vegetation. Commanders will rarely have visual contact with all elements or members of their unit.
Arm-and-hand signals are used in all types of operations. The effectiveness of arm-and-hand signals can be improved by insuring that each soldier understands the meaning of the signal and passes it on to others in his vicinity.
Pyrotechnics can be used in most conditions of visibility. Certain standard colors of smoke or flare signals have limited use because they blend in with vegetation (green) or offer little contrast with fog or haze (white). Careful selection of colors (such as red or yellow) which contrast with the background color of the jungle increases the effective range of pyrotechnic signals. The jungle canopy can affect the use of star clusters and parachute flares in two ways.
Overhead clearance required for firing flares, is limited.
Once clear of the canopy, the flare or star cluster may be hard to see by other ground units looking through the canopy. The disadvantage of pyrotechnic signals is that they can be easily seen and imitated by the enemy.
These means include both voice and devices such as whistles, horns, gongs, and explosives. Sound signals are used to attract attention, transmit prearranged messages, or spread alarms. They are good only for short distances. Range and reliability will be reduced by battle noise, weather, terrain, and vegetation. As they may also be heard by the enemy, they should be restricted for security reasons. Sound signals must be simple to avoid misunderstandings. The means for sound signals are usually prescribed by the unit SOP and communications-electronics operation instructions (CEOI).
These types are most secure and a good way to send long messages and documents. However, the speed of surface messengers is severely limited by jungle terrain and vegetation. The lack of roads restricts full use of motor vehicles. Foot messengers may have difficulties with land navigation and natural obstacles. The use of air messengers maybe a better alternative, but one that is limited by availability of aircraft, scarcity of good landing zones, weather conditions, and the fact that air activity aids the enemy in locating friendly troop areas. When using a messenger, messages should be written. Their text must be clear, concise, and complete.
These methods are established whenever feasible. Wire is more secure than radio, hard to jam, and allows conversation with break-in capability.
The heavy rain and high humidity of the tropics reduce the range (about 20 percent) and reliability of wire communications. Wire laying in the jungle requires more time and suitable wire laying routes are limited. The increased cover and concealment make it easier for the enemy to intercept or interrupt wire communications and to ambush maintenance crews. Wire laid by air on top of the jungle canopy is extremely difficult to maintain and recover; however, it is less likely to be damaged by vehicles or weather. Splices should be carefully made to avoid signal losses when wet.
Radio communications are normally the fastest means available but the least secure.
Effective radio communications in the jungle require emphasis on:
The usefulness of radio communications is reduced in jungle operations. VHF and UHF radios (FM radios included) are particularly limited by the jungle growth and terrain that absorb and obstruct the transmissions. It is not unusual for the range of a set operated in the jungle to be reduced by 10 to 25 percent of the normal range.
ANTENNAS AND FIELD EXPEDIENT ANTENNAS
In order to overcome environmental conditions in the jungle, existing antennas must be used properly and field expedient antennas produced to extend the capacity of current equipment.
To use existing antennas properly, the following items must be accomplished:
The problems of line-of-sight antenna locations and operations security are best solved by remoting the transmitter from the command post.
The AN/GRA-39 radio set control group allows the operator to remote the radio up to 3.2 kilometers away from the observation post. It should be noted that there is no practical advantage to be gained by installing the radio and antenna away from the command post (remoting) unless the distance is 1 kilometer or more. The error inherent in radio direction finding equipment does not provide for a consistent accuracy less than 1 kilometer.
Field expedient antennas will enhance the communications capacity of a unit operating in the jungle if they are properly constructed. WD-1 or portions of the RC-292 antenna can be used as the radiating element (antenna). Wood or plastic spoons can be used as insulators when insulators are not available. Resistors should be obtained through communications maintenance channels.
Useful field expedient antennas in the jungle are:
Field expedient RC-292
The standard issue RC-292 is a highly-effective, omnidirectional antenna. It is usually more effective than a whip antenna, and is particularly effective in the VHF range. With all its components, it weighs 48 pounds and two soldiers can erect it in 15 minutes.
Leaders should consider using field expedient versions of this antenna in the jungle for these reasons:
Portions of the RC-292 may be used to construct a field expedient antenna. Only the vertical sections, antenna base, ground plane sections, and transmission line are needed.
Another field expedient antenna can be constructed without using any of the standard RC-292 components. This antenna has various names such as the field expedient 292, the jungle antenna, and the field expedient ground plane antenna.
A third type of expedient antenna used in the jungle is the patrol antenna. It is the same as the jungle antenna minus the ground plane element. Insure that the length is determined by using the 1/2 wavelength instead of the 1/4 wavelength column of the chart. The range of the set will be increased 2 to 3 times its normal range. This antenna is easier to handle and construct.
RETRANSMISSION AND RADIO RELAY
With the decrease in range of most radios used in jungle operations, retransmission will be a good method to improve communications. Commanders should consider establishing retransmission sites and using additional signal personnel. Radio relay sites, either airborne or on high terrain, will also improve radio communications between stations.
EQUIPMENT MAINTENANCE IN THE JUNGLE
Moisture commonly found in the jungle environment can result in numerous outages of communications-electronic equipment.
The following measures, combined with normal maintenance, will help counteract the problems.
When radios are protected by plastic bags, make sure the battery vent is not obstructed. Radios protected in this manner must be constantly checked to insure moisture does not build up in the bag. Clean radios as frequently as individual and crew-served weapons are cleaned.
In the past, jungle enemies have relied heavily on friendly radio messages as primary intelligence sources. Communications security denies or delays unauthorized persons from gaining information from telecommunications.
Radio operators should use the following antijamming procedures to thwart enemy jamming efforts.
Recognition. The first thing an operator must do when there is interference on his radio is to try to find its cause. As symptoms of jamming are often similar to other types of interference, he should not assume that it is jamming. If the interference decreases when the receiver antenna is removed, the interference is jamming; if it does not, the interference is generated inside the receiver.
Continued Operation. Normal radio operation is continued once jamming has been identified so that the enemy cannot determine the effect of his jamming. The rule is: during jamming, operators continue operating unless ordered to shut down.
Reporting. All operators must report jamming to their next higher headquarters, by another means of communications; for example, wire or messenger. A typical jamming report tells date and time of jamming, frequencies affected, type and strength of jamming signal, and designation of the unit making the report.
The exact format of the report is found in the unit's CEOI.
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