The AN/PRC-104 (fig. 11-5A, 11-5B, and 11-5C) is a state-of-the-art lightweight radio transceiver (transmitter and receiver combined) that operates in the high frequency (hf) and upper part of the low frequency (lf) portions of the radio spectrum. The receiver/ transmitter circuits can be tuned to any frequency between 2.0000 and 29.9999 MHz in 100 Hz increments, making it possible to tune up to 280,000 separate frequencies. The radio set operates in the upper sideband (USB) or lower sideband (LSB) modes for voice communications, CW for morse code, or frequency shift keying (FSK) for transmission of teletype signals or other data. In the man-pack configuration the radio set is designed to be carried and operated by one manor, with the proper accessories, the radio set can be configured for vehicular or fixed-station use.

The control panel (fig. 11-6) was engineered for ease of operation by making it possible for the operator to adjust the front panel controls-even while wearing heavy gloves. Unlike older, similar radio sets, there are no front-panel meters or indicator lights on the AN/PRC-104. The functions that formerly required these types of indicators (antenna tuning, battery condition, etc.) are monitored by the radio itself and communicated to the operator as special tones in the handset. This feature is particularly useful during tactical black-out operations. The superior design and innovative features of the AN/PRC-104 radio set now make it possible to maintain a reliable long-range communications link using lightweight, portable equipment that can be operated by personnel with a minimum amount of training.

RADIO SET.- The AN/PRC-104 radio set consists of three units: (fig. 11-7) low-power receiver-transmitter RT-1209/URC (receiver/exciter), 20-watt radio frequency amplifier AM-6874/PRC-104 (amplifier/coupler), and battery case CY-7541/ PRC-104 (battery pack). Quick-disconnect latches secure the receiver/exciter to the amplifier/coupler, and each is latched to one end of the battery pack When latched together, the receiver/exciter is electrically interconnected with the amplifier/coupler through a built-in connector; the battery pack power is connected to the amplifier/coupler. All of the operator controls and connections are located on the receiver/exciter front panel, except for the antenna select switch and antenna connections located on the amplifier/coupler unit. They are constructed on a die-cast aluminum housing; the battery pack housing is tough plastic. Watertight seals for the covers and panels make the three units watertight, submersible, and capable of rough handling and abuse in any field environment. The unit circuits are modular for ease of repair. The total weight of the assembled AN/PRC-104 (three units with battery) is 14 pounds, making it a lightweight and easily carried package.

MAN-PACK OPERATION.- The basic man-pack configuration (fig. 11-8) consists of the radio set (three units), a whip antenna, and an audio input/output device. Antenna AT-217A/PRC is a 10-foot standard whip antenna that screws into the Spring Section Antenna AB-129/PR (shock mount) which, in turn, screws into the antenna mount on the amplifier/coupler. The whip antenna is adequate for most short-range requirements (less then 10 miles). Two standard input/output devices come with the radio set: Handset H-189/GR and Telegraph Key KY-872/PRC-104. These are attached to either of the two AUDIO connectors on the receiver/ exciter. The radio transmitter (exciter) is enabled (keyed) by the handset push-to-talk (PTT) button or by depressing the telegraph key to contact. The receiver is operative only when the transmitter is disabled;

Figure 11-5A.-Radio Set AN/PRC-104 equipment supplied.

Figure 11-5C.-Radio Set AN/PRC-104 equipment supplied.

Figure 11-6.-AN/PRC-104 controls and indicators.

Figure 11-7.-Radio set installation and setup.

therefore, communication is on a one-way reversible (half-duplex) basis. The radio set with whip and handset weighs 15.7 pounds.