The AN/PRC-77 radio set shown in figure 11-1 is a short-range, man-packed, portable, frequency-modulated (FM) receiver-transmitter used to provide two-way voice communication. The AN/PRC-77 operates on low power and at very high frequencies (vhf). The location of the equipment greatly affects its operating range. Normally, a line-of-sight range can be expected; that is, when the other station can be seen,

Figure 11-2.-Operating instructions for Radio Set AN/PRC-77.

satisfactory operation improbable. An intervening hill or a tall building may hamper or prevent contact with other stations.

Valleys, densely wooded areas, and low places are poor sites for setting up communications. A hilltop or a tower location increases the operating distance. When possible, avoid locations near a source of electrical interference, such as power or telephone lines, radar sets, and field hospitals.

The AN/PRC-77 consists of a receiver-transmitter (Radio RT-841/PRC-77) and minor components. The receiver-transmitter is held in the receiver-transmitter case by four screws. The battery box is attached to the receiver-transmitter case by two clamps . The complete unit, when assembled, is watertight. All controls are located on the front panel. A battery plug projects from the receiver-transmitter and mates with the connector of the battery. The power for this set is provided by a BA-4386 magnesium-alloy battery that enables the radio to operate for about 30hours before a replacement battery is needed.

Minor components include a cotton duck harness (ST-138/PRC-25) so the radio can be strapped to the operator's back; a short antema (AT-892/RC-25) for general, short-range service; a six-section, long antenna (AT-271A/RC) for maximum range; and antenna support (AB-591/PRC-25) for use with the long antenna; a handset (H-189/GR) that consists of a microphone and receiver for transmitting and receiving signals; and a cotton duck bag (CW-503/PRC-25) that is divided into several pockets used to store the two antennas, the antenna support, and the handset. Operating instructions for the AN/PRC-77 are shown in figure 11-2.