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LESSON 2
TACTICAL CONTINUOUS WAVE AND VOICE RADIO EQUIPMENT
CRITICAL TASKS: 01-5878.04-0005,
01-5778.07-0003, 01-5778.07-0007
OVERVIEW
LESSON DESCRIPTION:
In this lesson you will learn the different types of tactical radio sets currently in use and how to select a particular set for a given communications task.
TERMINAL LEARNING OBJECTIVE:
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ACTIONS: |
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CONDITION: |
You will be given information from this lesson. |
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STANDARD: |
To demonstrate competency of the terminal learning objective, you must achieve a minimum score of 70% on the subcourse examination. |
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REFERENCES: |
The material contained in this lesson was derived from the following publications: FM 24-18 and TC 24-24. |
The rapid changes in communications technology are constantly bringing new and better equipment to the market for use in the field. This lesson will present some of the equipment currently used as well as equipment which is being phased-out. Even though a piece of equipment may be outdated, you may still run across it in reserve units or you may have occasion to use a piece as a backup to a failed modern unit. It is important, therefore, that you know how this older equipment operates and what its capabilities are. Since this lesson is merely an overview and is in no way a complete technical description of any piece of equipment, you are encouraged to read the technical manuals on each piece of equipment in order to become thoroughly familiar with its capabilities. However, review of these technical manuals is not required for completion of this subcourse.
1. Transmitting Set AN/PRT-4, AN/PRT-4A.
TM 11-5820-549-12 details this equipment. The AN/PRT-4 and 4A are hand-held, low-power FM transmitters. These sets are generally considered obsolete and are no longer in much use. They transmit over a relatively short distance in the low VHF region (47 to 57 MHz). They were formerly used primarily at the squad and platoon level for the leader to communicate with unit personnel.
2. Receiving Set AN/PRR-9.
TM 11-5820-549-12 details this equipment. This is the receiver that was used in conjunction with the AN/PRT-4 transmitter in the squad or platoon. It mounts on the soldier's helmet or webbing and has an earphone jack for quiet reception. As with the AN/PRT-4, this equipment is obsolete.
3. Radio Sets AN/PRC-25, AN/VRC-53, and AN/GRC-125.
TM 11-5820-398-12 (PRC-25) and TM 11-5820-498-12 (VRC-53, GRC-125) details these sets. This family is the earliest group of FM transmitter-receiver radio sets still in use. All three versions utilize the RT-505 transmitter-receiver operating in the lower VHF band (30 to 52.95 MHz and 53 to 75.95 MHz). The PRC-25 is a portable manpack version. The VRC-53 adds amplifier OA-3633 to make a vehicular-based unit, and the GRC-125 is a portable or vehicular based model. All three configurations are used for short-range communications. This family of radio sets has no secure transmission capability.
4. Radio Sets AN/PRC-77, AN/VRC-64, and AN/GRC-160.
TM 11-5820-667-12 details these sets. This family of radio sets is replacing the PRC-25, VRC-53, and GRC-125 series respectively. The transmission characteristics are exactly the same as the earlier radio sets. The difference is that the newer sets use transmitter-receiver RT-841 which is completely transistorized. Another feature incorporated into the new sets is the capability of secure voice transmission using the VINSON device.
5. AN/VRC-12 Family of Radio Sets.
These sets and their components are detailed in TM 11-5820-401-12. The radio sets in the AN/VRC-12 family are short-range vehicular and fixed radio sets designed for general tactical use. They provide FM voice communications and can be used with secure voice and digital data equipment using the X MODE facility. Two of the sets (AN/VRC-45 and AN/VRC-49) have retransmission capability. The radio sets of the AN/VRC-12 family will net with each other and with other FM radio equipment operating in the 30 to 75.95 MHz frequency range. Each of the eight configurations in this family is made up of a combination of receiver-transmitters RT-246/VRC and RT-524/VRC and receiver R-442/VRC along with support equipment.
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Receiver-transmitter RT-246/VRC and RT-524/VRC. These two receiver-transmitters are the heart of the AN/VRC-12 family of radios. They operate in two bands; Band A - 30 to 52.95 MHz, and Band B - 53 to 75.95 MHz. They are capable of transmission up to about 41 kilometers (km). Each member of the AN/VRC-12 family contains at least one of these units. The primary differences between the two units are that the RT-246 has ten automatic channel presets and the RT-524 has a built-in loudspeaker.
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Receiver R-442/VRC. This receiver is used in several of the AN/VRC-12 configurations to allow monitoring one net while transmitting in another. The R-442 operates in the same frequency range as the RT-246 and RT-524.
(1) AN/VRC-12. This configuration includes one RT-246, one R-442, and two antennas. You can use this configuration to monitor one net while you conduct communications in another. You can easily switch transmitting frequencies of the R-246 to transmit in the R-442's net.
(2) AN/VRC-43. This configuration consists of one RT-246 and one antenna and it is used for communications in a single radio net.
(3) AN/VRC-44. This configuration consists of one RT-246, two R-442s, and two antennas. With this set you can communicate in one net and monitor two additional nets. As with the VRC-12, you can change transmitting frequency on the RT-246 and transmit into either of the other two nets.
(4) AN/VRC-45. This configuration consists of two RT-246s, two antennas, and a C-2299/VRC Retransmission Cable Kit. You should use this configuration to provide retransmission facilities for two stations that are too far apart to talk to each other directly. You can also use this set to retransmit information from one net into another net by tuning the two RT-246s to different frequencies.
(5) AN/VRC-46. This configuration uses one RT-524 and one antenna and is essentially identical in function to the AN/VRC-43.
(6) AN/VRC-47. This configuration uses one RT-524, one R-442, and two antennas. It functions the same way as the AN/VRC-12.
(7) AN/VRC-48. This set consists of one RT-524, two R-442s, and two antennas. It functions the same way as the AN/VRC-44.
(8) AN/VRC-49. This configuration consists of two RT-524s, two antennas, and the C-2299/VRC. It serves the same retransmission functions as the AN/VRC-45.
All the AN/VRC-12 family configurations are secure voice capable. You can secure the sets using either VINSON (KY-57) or NESTOR (KY-38) security devices.
6. Radio Set Control AN/GSA-7.
TM 11-5135-15 details this equipment. The AN/GSA-7 is an electronic switching device. You use it to interface FM radio equipment with local push-to-talk wire telephone circuits. The GSA-7 is the basis of the Net Radio Interface (NRI) system. The unit acts as an automatic keying device so that when a remote telephone operator keys his telephone set he also keys the transmitter of the FM radio set. This allows his wire telephone message to transmit over the FM frequency to a receiver that can also be attached to another GSA-7 to convey the message into another wire telephone net at a remote site. You can control a radio set with the GSA-7 from as far away as 16 km (7.3 miles).
7. Control Group AN/GRA-6.
TM 11-5038 details this equipment. Occasionally you may want to locate your radio transmitter in a site where communications are good, but the site does not offer a good tactical position. When this happens the best thing to do is set the radio up so you can operate it remotely. The GRA-6 is the piece of equipment that allows you to do this. The GRA-6 consists of a local and remote unit used at the radio site and the remote control site respectively. The two units are connected by field wire and can be separated by up to 3.2 km or 1.5 miles.
8. Radio Set Control Group AN/GRA-39B.
TM 11-5820-477-12 details this equipment. The GRA-39B is another remote control set similar to the GRA-6. It also is used with FM radio sets and has a range of 3.2 km. The principal difference between the GRA-39B and the GRA-6 is that the 39B is fully transistorized and the 6 is not.
9. Retransmission Cable Kit MK-456A/GRC.
This kit is used with the AN/PRC-25 and AN/PRC-77 series of radios for retransmission. You can also use it with the AN/VRC-12 series if the standard C-2299/VRC kit is unavailable.
10. Radio Set AN/GRC-19.
TM 11-5820-295-10 details this equipment. The AN/GRC-19 is a medium-power voice and continuous wave radio set designed for vehicular installations. It forms the central unit for several of the older RATT sets. The GRC-19 is being phased-out of use and replaced with the newer GRC-106 radio set. You can also use the GRC-19 to perform retransmission functions. Both transmitter and receiver operate in the HF band. The transmitter operates between 1.5 and 20 MHz, and the receiver operates between 0.5 and 32 MHz. The AN/GRC-19 operates in AM/DSB mode.
TM 11-5820-520-12 details this equipment. As stated previously, the AN/GRC-106 is replacing the AN/GRC-19 in its mobile retransmission role. It is also the central unit for the newer family of radio teletypewriter sets currently in use. The GRC-106 operates in the HF band between 2.0 and 29.999 MHz and uses the AM/SSB mode. There are two basic configurations of this equipment, the GRC-106 and GRC-106A. The former uses receiver-transmitter RT-662/GRC which has a channel spacing of 1 kHz. The A variation uses receiver-transmitter RT-834/GRC which has channel spacing of 100 Hz. You can see from this that the A variation has ten times as many channels available as the standard GRC-106. The AN/GRC-106 has both voice and CW capability.
TM 11-5820-554-15 details this equipment. The FRC-93 is a commercial type of AM/SSB (upper or lower) radio set adapted for military use. You can also perform CW communications using the FRC-93. The radio set operates in two regions of the HF band, from 3.4 to 5.0 MHz and from 6.5 to 30 MHz. This type of radio set uses crystal sets for tuning.
TM 11-5820-590-12 and TM 11-5820-590-12-1 details this equipment. The AN/PRC-74 is a low-power, transistorized AM/SSB/USB radio set designed for voice and CW communications. The PRC-74 is configured as a manpack and is primarily designed for communications in areas where LOS communications is not possible due to terrain or other obstructions. The AN/PRC-74 comes in four variations: basic, A, B, and C. The basic and A versions operate between 2.0 and 11.999 MHz. The B and C versions extend the upper frequency limit to 17.999 MHz. The AN/PRC-74 adds the versatility of being able to communicate with remote sites that you could not communicate with using the AN/PRC-25 or 77 series of FM radios.
14. Radio Set AN/PRC-70.
TM 11-5820-553-10 details this equipment. The AN/PRC-70 was originally designed to give special forces, ranger, long-range reconnaissance patrol, and selected engineering units a light-weight multimode means of communications. The unit operates over a range of 2.0 to 75.999 MHz in the HF and VHF bands. The PRC-70 can operate in AM/DSB, AM/SSB, FM, CW, and frequency-shift keying (FSK) modes. This flexibility allows the unit using this device to travel almost anywhere they need to go and still be able to provide real-time intelligence information to command and control units in the corps and theater areas. The AN/PRC-70 usage has been expanded to battalion communications stations as well as forward deployed units. The AN/PRC-70 can be operated in secure mode using both VINSON and NESTOR security devices. Another great advantage of the PRC-70 is that it can communicate with any of the AM, AM/SSB, or FM radios discussed previously in this lesson. You can also set up retransmission stations using the PRC-70 as illustrated in figure 2-1. The combination of its light weight, ruggedness, and wide range of capabilities makes the AN/PRC-70 an ideal radio set for units that require great freedom of movement and activity. In a fixed site, one AN/PRC-70 can serve as a backup for almost all other tactical communications systems.
Figure 2-1. AN/PRC-70 retransmission configuration
15. Summary.
This lesson has introduced you to the various pieces of equipment used in tactical radio communications, along with the uses for and capabilities of each piece of equipment. In the next lesson you will learn the basic procedures of voice communication over tactical radio channels.
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