Military

APPENDIX F

Communications Planning and Troubleshooting

This appendix provides information and methods for communications planning and troubleshooting for the ADA sensor platoon and sections. Communications is the lifeline of the platoon leader's command and control of his sections. Sections must be able to communicate to pass EW information. FMs 24-18 and 24-24 contain further information for solving communications problems.

COMMUNICATIONS PLANNING

The number and types of communications equipment within the ADA sensor platoon vary and are dependent upon the type of unit to which the platoon is assigned. The Communications Planning Factors illustration below provides some planning factors to include distance and power requirements. Platoon leaders should pay attention to the numbers and types of batteries required to run their communications equipment.

Figure F-1.

Figure F-1a.

SINGLE-CHANNEL GROUND AND AIRBORNE RADIO SYSTEM

SINCGARS is the newest family of radios in use by the US Army. The SINCGARS radios make use of extensive large scale integration (LSI) circuitry, including microprocessors. A key element in the radios, the frequency synthesizer, uses new techniques to generate the required frequencies. It also provides facilities to enable the sets to operate with conventional radios. SINCGARS operate in the 30- to 88-megahertz frequency range in 25-kilohertz steps for a total of 2,320 channels. It can operate in either a single-channel or frequency-hopping mode.

RADIO SET, AN/VRC-87

The AN/VRC-87 is a short-range, vehicle-mounted radio set with a solid-state, securable transceiver intended for VHF-FM tactical operations. The AN/VRC-87 is used where the communications range is normally 8 kilometers or less. The configuration is used by the ADA platoon, headquarters battery, and similar applications. The capabilities are the same as the AN/PRC-119 manpack radio, except the AN/VRC-87 cannot be used in a dismounted role. The AN/VRC-87 replaces the AN/VRC-64 radio (see the AN/VRC-87, -88 illustration).

RADIO SET, AN/VRC-88

The AN/VRC-88 is a vehicle-mounted radio that has a manpack antenna, and a battery case as additional components. The radio can be removed from the vehicle, and by installing the antenna and battery case, can be reconfigured as an AN/PRC-119 manpack radio. The AN/VRC-88 has a 4-kilometer range and may be operated from a vehicle or in a dismounted configuration. It provides more channels, reduces operator burden, and increases equipment reliability. The AN/VRC-88 is used by soldiers to communicate from vehicles or from dismounted positions. It is the replacement for the AN/GRC-160 radio (see the AN/PRC-119 Manpack Radio illustration).

RADIO SET, AN/VRC-89

The AN/VRC-89 is a vehicle-mounted, dual-configuration radio consisting of one short-range and one long-range, solid-state, securable transceiver intended for VHF-FM tactical operations. The AN/VRC-89 provides long-range (up to 35 kilometers) and short-range (up to 8 kilometers) operation in two nets simultaneously. The AN/VRC-89 is a dual-radio configuration mounted on a single vehicular mount. It replaces existing AN/VRC-47 configurations, as well as separate configurations of AN/VRC-64 or AN/VRC-46 in a single vehicle. The AN/VRC-89 is basically two vehicular-mounted, short-range radio sets with an added power amplifier that provides one of the radio sets with a long-range communications capability up to 35 kilometers (see the AN/VRC-89, -91 illustration).

Figure F-2.

Figure F-3.

Figure F-4.

RADIO SET, AN/VRC-90

The AN/VRC-90 is a long-range, vehicle-mounted radio set with a securable transceiver intended for VHF-FM tactical operations. The AN/VRC-90 is used where the communications range must normally operate over long distances (up to 35 kilometers). The AN/ VRC-90 vehicular configuration is used by individuals and crews that require continuous, long-range communications in a net. The radio configuration is used throughout the Army at all echelons from corps through platoon. The AN/VRC-90 replaces the AN/VRC-46 radio (see the AN/VRC-90 Vehicle Radio illustration).

RADIO SET, AN/VRC-91

The AN/VRC-91 is a vehicle-mounted, dual-radio configuration consisting of one long-range and one short-range dismountable, solid-state, securable transceiver intended for VHF-FM tactical operations. The AN/VRC-91 provides long-range (up to 35 kilometers) and short-range dismountable (up to 8 kilometers) operation in two nets simultaneously. The AN/VRC-91 vehicular, long-range/short-range man-pack configuration provides maximum flexibility. The AN/VRC-91 basically combines the features of the AN/VRC-88 and AN/VRC-90 into a single-vehicle installation. The AN/VRC-91 replaces the AN/ GRC-160 radio when teamed with the AN/VRC-46 in a single vehicle (see the AN/VRC-89, -91 illustration above).

RADIO SET, AN/VRC-92

The AN/VRC-92 is a vehicle-mounted, dual-radio configuration consisting of two long-range, solid-state, securable transceivers intended for VHF-FM tactical operations. The AN/VRC-92 also has an automatic retransmission capability. It is used to meet dual, long-range (up to 35 kilometers) communications requirements. The AN/VRC-92 is also used for VHF-FM retransmission operations. It is basically a AN/VRC-88 with an additional power amplifier mount to provide communications range up to 35 kilometers to the second radio system. This configuration replaces two separate AN/VRC-46 radios in a single vehicle and the AN/VRC-49 radio. Because of the automatic retransmission capability found in each SINCGARS, all AN/VRC-92 configurations are capable of automatic transmission (see the AN/VRC-92 illustration).

Figure F-5.

Figure F-6.

SINCGARS

It is anticipated that the latest version of SINCGARS will include integrated communications security (ICOMS) devices and will be fielded as soon as practical. The SINCGARS Configurations illustration illustrates the crosswalk from the AN/VRC-112 series radios and the replacement SINCGARS radios.

Figure F-7.

RADIO TROUBLESHOOTING

Moisture, dust, and corrosion are the main culprits in radio problems. Here are a few steps to try before calling the radio repairman:

  • Check for water in the antenna matching unit. There is a small Phillips head screw used as a drain plug. Remove and let water drain out--allow to dry-- replace the plug.

  • Check that the matching unit is matching. Move the frequency knobs at the base. They should automatically return to the proper broadcast frequency. Dust may be binding the knobs. Clean the base off. Match the frequency manually, if required.

  • Check the antenna wire connection at the base. Remove the wire and clean the connections with a pencil eraser and reconnect. Be sure the radio is off for this procedure.

  • Check the antenna cable for cuts.

  • Check the whip antenna for breaks. Repair is covered later in this appendix.

  • Check the handset and speaker connections and clean with pencil eraser, as needed.

  • Check the handset and speaker connections for rubber O-rings. If not present, change headsets. Check for nicks and dry rot and replace as needed. Lubricate the O-ring with silicone or saliva on the finger and install.

  • Check the vent fan at the back of the radio for dust and freedom of movement.

  • Check the ground wire connection and tighten or reconnect as necessary.

  • Check the seating of the radio. Pull the radio forward and check the cleanliness and straightness of the pins and plug. Reseat and secure the radio.

  • If using a portable system, check the batteries and contact points. Clean as needed and or replace the batteries.

  • Do not open the case. If repairs go beyond these steps, get a repairman. Use an alternate radio or means to communicate.

  • If you still cannot get through, try moving to higher ground away from power lines or obstructions.

  • Try pointing the vehicle in the direction of the station to which you are sending.

  • Try setting up an OE-254/GRC if you are stationary for a time.

  • Set up a directional antenna to avoid being located by RDF, or if greater distance is needed. Directional field-expedient antennas are covered later in this appendix.

  • If using AM, try tying the whip antenna using the tie-down cords so that the angle is approximately 45 degrees from vertical to achieve the near vertical incidence sky-wave (NVIS) antenna effect (FM 24-18).

WIRE COMMUNICATIONS TROUBLESHOOTING

The same problems that affect radios can affect the wire and telephones. WD-1/TT is very durable, but it can break down due to wear and splicing. There is no substitute for checking your equipment prior to going to the field. Try these steps:

  • Have the DR-8 reels checked for conductivity. If they fail, trade them in for new ones.

  • Once the hot loop has been run, check the line by hand. Look for cuts, splices, and kinks. If the distance is short, replace the line. If replacement is not practical, splice the wire according to the following illustration.

  • If the ground is wet, try elevating the line overhead high enough not to cause problems.

If the wire is not the problem, telephones need to be checked. Try the following telephone checks during troubleshooting:

  • Check the phone location. If the wire comes in higher than the phone, make a rain loop. The rain loop is a loop lower than the phone that allows rain to drop off prior to flowing down the line and shorting the connectors.

  • Check the connections to determine if the connector is caught on the insulation.

  • Check the selector switch. In most cases, the indicator should be in the local battery (LB) position. The other positions, common battery (CB) and common battery signaling (CBS) system, are normally used in garrison. Check to ensure the INT- EXT switch is in the INT position when using the handset. Use the EXT position if using the H-144/U auxiliary handset-headset.

  • Check the batteries and contact points. Clean the contacts with a pencil eraser and change the batteries, as needed.

  • If the temperature is low or the humidity is high, use the moisture shield supplied with the phones. These screens go over the mouthpiece on the outside of the handset.

  • Check the connection of the mouthpiece. Remove the cover and check the contact points. If moist, allow to dry; if corroded, clean off with a pencil eraser and reinstall.

  • If your problems go beyond this, have a technician check them out.

If using the SB/993-GT, be sure the connections are tight and that the posts are clean. Rain loops should be used to keep moisture problems to a minimum.

Figure F-8.

FIELD-EXPEDIENT ANTENNAS

Tactical antennas sometimes break or may be rendered inoperative. It is the responsibility of the leader and his RTO to be prepared for this. The following steps and procedures help keep communications working in an effective manner.

WHIP ANTENNA REPAIR

If the whip antenna is in two separate pieces and you have both pieces, clean the areas to be connected. Use a knife to clean away insulation so that matching contact points will touch, creating a connection. Find a branch or pole to act as a supporting splint. Secure the splint to the lower section allowing about half to overhang for support of the upper section. Secure with duct tape, wire, or cord. Slip the upper portion on to the splint and be sure the connection points make contact and are secure, as you did the lower half. If the antenna is broken but not severed, shore up the broken end using a splint as above. If the upper portion of the antenna is missing, use a length of WD-1/TT equal to the length of the missing piece. Clean about 4 inches of insulation from the wire. Expose the center wire of the lower portion of the antenna. Connect the WD-1. Use a pole roughly the length of the original antenna mast. Secure the pole to the lower portion, then secure the WD-1 to the pole. The length of the antenna is critical. The antenna length should be same as the length of the antenna it is replacing.

DIRECTIONAL HALF RHOMBIC ANTENNA

Field-expedient antennas require the use of items on hand. The Insulators illustration shows some improvised insulators. The insulator is used to insulate the radiating element (main wire) of the antenna from other objects.

Figure F-9.

The length of the field-expedient antenna should be two or more wavelengths long and suspended between 3 and 20 feet off the ground. The Wavelength Calculations illustration shows the calculation of wavelength. The following is a list of materials needed to construct an antenna:

  • Field wire.

  • Measuring system (ruler/tape measure).

  • Pole system (camouflage supports work well).

  • Wire cutter/stripper.

  • 600-ohm, 1-watt resistor or expedient (see the Resistors illustration).

  • Ground stakes.

  • Adapter UG-1441--red for radiating element and black for counterpoise (ground).

Construct the antenna according to the Half Rhombic Antenna illustration. The broadcast direction is in line with the resistor. The long-wire antenna has the same equipment list as above. Construction is shown in the Long-line Antenna illustration.

WAVELENGTH CALCULATIONS

Wavelength (in meters) = 300,000,000(meters per sec) / Frequency (hertz)

or

W (wavelength) = V (velocity) / F (frequency)

Example of calculation of wavelength for frequency: 35.95 MHz (35.95 x 1,000,000)

Wavelength = 300,000,000 / 35,950,000 = 8.34 meters

Conversion to feet: 8.34 m x 3.3 = 27.54 ft (one wave)

Figure F-10.

Figure F-11.

Figure F-12.

ALTERNATE COMMUNICATIONS TECHNIQUES

Air defense is only one of seven BOSs. Each of the BOSs have representatives down to the battalion level and all have radio communications to their own elements. Try borrowing a radio or sending quick messages or asking for assistance in relaying your message. The fire support element (FSE) has the TACFIRE system which can be used to send hard copy traffic. The drawback to this method is that it is a temporary fix and is subject to the host radio traffic requirements. If the manpower and transport are available, a messenger may be used. This is the most secure method of sending a message, but it is also the most time-consuming and may expose the messenger to hostile fire. If you are in a situation where your subelement can hear but not send and they can break squelch, instruct them to reply to yes and no questions by breaking squelch. If both stations can only break squelch, try using Morse code. The Morse code is shown in the following illustration. The drawback to Morse code is that it is a constant transmission and is time-consuming. Check the local TSOP for instructions on using smoke or sound and light signals for communications. Care must be taken not to give away your position when using these methods. The important thing is to get the message through; be as innovative as needed. It is important to have a backup communications plan in the form of alternate frequencies and TSOP procedures. This plan takes effect when communications have been lost or degraded.

Figure F-13.



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