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CHAPTER 9

COMMUNICATIONS


9-1. COMMUNICATIONS EQUIPMENT

The cannon battery or platoon uses both radio and wire equipment. Either system will become primary or secondary, depending on the tactical situation and the availability of equipment. There are advantages and disadvantages associated with each. For example, radio permits mobility and speed but is susceptible to enemy electronic warfare (EW). Wire lines are more immune to enemy EW, but they inhibit rapid movement and speedy installation. Hence, the strength of one becomes the weakness of the other. Therefore, it is reasonable to view the battery or platoon communications (comm) system as that which makes the best use of the radio and wire resources available at any given time. We must always strive to have a system redundant to the one being used, be it radio or wire. Ideally, it would be best to rely first on radio during displacements and initial site occupations. Then, if time permits, install and operate on wire lines. If radios are unavailable, or unusable, a wire system is necessary. Accordingly, the diagrams and system configurations which follow provide practical and realistic ways of establishing battery commo systems, depending on which TOE a unit uses.

9-2. BATTERY COMMUNICATIONS SECTION

a. To help the battery commander meet communications requirements, a comm section is authorized at the battery level. This section gives battery personnel technical assistance in the installation, operation, and maintenance of the battery comm system. Battery personnel share responsibility for installing, operating, and maintaining the battery comm system.

b. The battery comm chief advises the commander on communications matters. The two wiremen help install and maintain the intrabattery wire system and wire equipment. The comm chief's specific responsibilities are as follows:

(1) Provide communications training to battery personnel and technical assistance for communications training in the unit.

(2) Advise the BC on communications considerations during selection of positions.

(3) Supervise the maintenance of comm equipment in the battery.

(4) Coordinate with the battalion comm chief on matters of personnel, communications security (COMSEC) materials, equipment, parts, maintenance support, and communications training.

9-3. BATTERY WIRE SYSTEM

a. Presently, the FA battery or platoon relies on wire to meet its internal communications needs. Three DR-8s are issued to each howitzer section so the battery can have a separate voice, digital, and advance party capabilities.

b. There are changes to the wire terminals used in the battery wire system. The SB-16 is no longer recommended for digital communications. The terminal strip TM-184 provides a cleaner, more reliable digital signal. The TM-184 (NSN 5940-00-238-8493) is a class IX item and can be procured through the unit supply system. Four TM-184s will be required to install the battery or platoon wire system. One will serve as the voice wirehead, one as the digital wirehead, and one for an advance party capability. The fourth connects battalion wire lines. Two additional TM-184s are required for the second platoon in a platoon-based battery.

(1) Advance party. The advance party wire system (Figure 9-1) provides immediate voice communication upon arrival of the main body, between each howitzer, the aiming circle, and the FDC.

(a) When the advance party arrives at a new location, a designated platoon representative places a voice wirehead (TM-184) in the position area, usually near the platoon center behind the gun line. This will allow personnel to troubleshoot most of the wire system from behind the gun line.

(b) Using a DR-8 (¼-mile reel), the gun guides connect the running end of each wire line to the appropriate pair of line binding posts on the voice wirehead. After this connection is made, the wire lines are tied off to a stake next to the voice wirehead and are tagged. Each gun guide then routes the wire from the voice wirehead to his gun position and connects it to the line binding posts on his telephone set TA-312 or headset-chestset, sound powered H-200. It is advisable to route wire lines to a stake forward of the gun line, as illustrated in Figure 9-1, to avoid wire line damage by vehicles moving in with the main body. However, the chosen wire line route will be dictated by terrain and available wire.

(c) The FDC representative also installs a wire line from the voice wirehead to the FDC position by using a DR-8. The running end of the wire line is connected to the appropriate pair of binding posts on the voice wirehead and tied off to a nearby stake and tagged. The wire line is then routed to the vicinity of where the FDC will be positioned and is connected to a TA-312, H-200, or an AN/GRA-39.

(d) To complete the voice wire system, a battery or platoon representative installs a wire line to the aiming circle from the voice wirehead. After this circuit is completed by installation of a telephone set TA-312, or H-200, the telephone system will allow the howitzers to be laid when the main body occupies the firing position.

(2) Main body occupation. Soon after the main body is in position, a second wire system is installed for digital communications.

(a) A second TM-184 (digital wirehead) is also placed near the battery or platoon center behind the gun line. The procedure for installing this system is identical to that used by the advance party, except the wireline is connected to the GDU at the howitzer and to the BCS in the FDC (Figure 9-2). In the howitzer, the wire line is connected to the BCS binding posts (labeled BCU) of the case assembly (Figure 9-3). The wire line at the FDC is routed into the vehicle and connected to the wire line adapter of the BCS (Figure 9-4). Stakes should be used at the howitzer and the FDC to secure incoming wire lines to reduce damage to the wire system by moving vehicles and personnel. Again, if terrain and available wire permit, the digital system should be routed to the front of the gun line to minimize system damage.

CAUTION
Avoid any ringing-type comm device on the digital line, as they have the potential to destroy the GDU case assembly.

(3) Complete system. If time and assets permit, a wire line can be installed as necessary between the BCS of the two platoon FDCs by using an RL-27 and RL-159 (Figure 9-5). This wire line can be used as necessary to hand off digital fire missions between FDCs. As time and mission allow, SB-22 switchboards can be installed in each platoon and connected by wire line to a battery command switchboard (SB-22) providing voice communications. In battery based operations (Figure 9-6), only a battery command switchboard is installed. Additional voice or digital capability can be provided by a battery wirehead that interfaces with battalion voice and digital wire lines. In most cases, external communications rely primarily on radio communications (and mobile subscriber equipment). The extent to which wire is installed and lines are improved or protected depends on the anticipated time the firing unit will stay in position before moving again.

c. All wire lines should be identified by tagging them individually at each end as outlined in TC 24-20 and at each stake. This facilitates troubleshooting the wire system. Wire tags should be prepared and labeled in accordance with the unit signal operating instructions (SOI) and SOP.

9-4. BATTERY RADIO NET STRUCTURE

The firing battery in a direct support (DS) battalion operates in two external radio nets and one internal radio net. Figure 9-7 shows the battery (btry) radio net structure. Listed below are the radio nets in which the battery operates and a description of how each net is used.

a. Battalion Command (Cmd) Net (FM-Voice). This is a secure net used for command and control and for intelligence information. The battalion (bn) operations and intelligence (O&I) element is the net control station (NCS). The battery commander, first sergeant, platoon leaders, platoon sergeants, platoon FDCs and the ammunition sections operate in this net.

b. Battalion Fire Direction Nets (FB1, FD2, FD3) (FM-Digital). These are tactical fire direction (FD) nets that are assigned one to each firing battery. The Bn FDC is the NCS for these nets. The assigned net (FD1, FD2, or FD3) is used to pass digital traffic. It may be converted to a voice net to fit operational needs. Each platoon FDC operates in this net and communicates digitally with the battalion FDC by using the BCS. The platoon FDC can also use this net as directed to communicate with the company fire support headquarters, forward observers, battalion fire support section, combat observation/lasing teams, aerial observers, and Firefinder radar sections.

c. Battery Command/Fire (CF) Net (FM-Voice and/or Digital). With the fielding of the small unit transceiver (SUT) AN/PRC-68 or AN/PRC-126 and the radio set single channel-ground and airborne radio system [SINCGARS]), each FA firing battery will have its own internal radio net.

(1) The L-edition TOE authorizes two AN/PRC-68s or AN/PRC 126s per howitzer section (one in the howitzer and one in the ammunition resupply vehicle, one per FDC, one per platoon leader, and one for the battery commander.

(2) The AN/PRC-68 or AN/PRC-126 can receive operating power from either the battery source or from a vehicular power system. In the hand-held mode, the AN/PRC-68 or AN/PRC 126 is powered by a 15.4 volt dry battery (BA-1588) that provides 24 hours of continuous operation. To operate the AN/PRC-68 or AN/PRC 126 with vehicular power, an amplifier-power supply OG-174 is required. The OG-174 allows the AN/PRC-68 or AN/PRC-126 to be mounted inside a vehicle, interfacing with the vehicle intercom. It provides an external antenna (Figure 9-8).

(3) Once the AN/PRC-68s or AN/PRC-126s are connected to the BCS and GDUs in the FDC and howitzers, respectively, the Battery CF Net can be used to pass digital traffic between the FDC and the howitzer sections. Once quality digital communications is established, voice communications should be discontinued and all headsets may be removed.

9-5. AN/PRC-68 AND AN/PRC-126 PLANNING CONSIDERATIONS

The AN/PRC-68 or AN/PRC-126 can be employed in a variety of tactical applications. However, limitations sometimes make it less than ideal. Therefore, wire communications should always be established if logistics, time, and tactical constraints permit. The AN/PRC-68 or AN/PRC-126 with OG-174 gives the FA cannon battery or platoon the capability to transmit digital as well as voice communications internally. Without the OG-174, the PRC-68 or AN/PRC-126 is used routinely for voice communications only in the hand-held mode. The following planning considerations are provided for use of the SUT:

a. The battery comm chief can set the AN/PRC-68 or AN/PRC-126 internally on one base frequency. Any frequency change will be a time-consuming process. Therefore, units should request a fixed, sole user frequency to be included in the SOI for the battery CF net.

b. The use of the AN/PRC-68 or AN/PRC-126 may need to be tailored to a particular mission. Their use during convoys, ammunition resupply, hip shoots, and advance party and main body operations may warrant a change in assignment of these radios.

c. Radio-electronic combat may preclude the use of the radio because of jamming.

d. Mutual interference between friendly units may preclude use of the radio.

e. Alternate frequencies to be used in case of jamming must be identified.

9-6. BCS-TO-GDU COMMUNICATIONS

The BCS-to-GDU link is the location of the most frequent problems. This area requires constant command attention if the maximum benefit is to be derived from the entire system. The following are the most common errors reported by or recommendations received from units worldwide:

a. BCS-GDU Wire Connection.

(1) Wire must be perfect.

(2) There must be a dedicated GDU wire with no splices.

(3) WD-1 was never meant for digital communications. One improper splice or one short may knock the entire system out. (Acquire copper wire WF 16U, NSN 6145-00-910-8847, for use with the GDUs.)

b. Gun Assemblies for Deflection and Quadrant. There must be enough slack in wire lines for shifting trails. Otherwise, wires or assemblies may be damaged.

c. Grounding.

(1) The case assembly on a howitzer must be properly grounded according to TM specifications. Otherwise, the system will malfunction, especially in wet weather or in early-morning dew.

(2) All wires and cables must be installed according to exact TM specifications.

d. Switchboard Use. Do not use an SB-22 or a similar device that requires a male end metal connector. Use a TM-184 or TM-125 type of terminal device.

e. GDU Power for Towed Unit. For GDU power, use a plug-in device to connect with the prime mover. Do not use a clamp connector to the vehicle battery since this will damage or destroy batteries and/or the GDU.

f. Mounts. All locally fabricated mounts should be inspected by comm technicians for proper power hookup and grounding.

g. Wire Setup Within the Position.

(1) A loop wire system from BCS to GDUs does not work. The vast and continuous amount of traffic in the system causes a loop to overload and malfunction or the guns will receive improper data.

(2) Failure to waterproof lines at the point of connection may cause loss of digital communications in wet weather. The plug-in terminal strip for GDU lines can be permanently mounted in a waterproof ammunition can with a hole drilled in the bottom for the lines to pass through. Once the lines are connected, the lid can be closed.

(3) The terminal strip should be centrally located so that each weapon uses no more than 400 meters of wire (one DR-8).

(4) Units must use a precise track plan and closely supervise movement of ammunition resupply vehicles to prevent damage or destruction of wire. Repair by splicing is unacceptable.

(5) Special positioning considerations for a platoonbased battery using one BCS is in Figure 9-9.

(6) Two wire lines must go to each gun-one voice and one digital. TA-312s should not be hooked up on the digital line once digital traffic begins.

h. NICAD Batteries. Nickel-cadmium (NICAD) batteries used in the GDU must be completely discharged before they are recharged. These batteries have a memory; unless they are discharged, they ultimately refuse to accept a recharge.

i. Digital Fire Commands. The section chief must view the entire digital fire command on every round. If in a hurry, he may see only charge, deflection, and quadrant. This creates obvious problems when FFE is entered or when shell, fuze, and/or fuze setting is changed.

j. Training. Observer, FDC, and howitzer section personnel must frequently participate in digital fire request loop training to get the maximum benefit from the BCS. The training set, fire observation (TSFO) is a tool which aids in this training.

k. AN/PRC-68 or AN/PRC-126 and GDU. The AN/PRC-68 or AN/PRC-126 (or other VHF-FM radio) can be connected to the case assembly, thus dispensing with wire to the GDU. Cables W33 or W34 are used for the signal, and W34 or W34A are used for power. (See TM 11-7440-283-12-2 and paragraphs 9-4 and 9-5 of this publication.)




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