INTRODUCTION TO COMMUNICATIONS LINK INTERFACE PLANNING SYSTEM

frequency hopping, no single carrier is used. Instead, the transmitter hops around the band in a random pattern, spending only a few milliseconds on any one frequency. This makes the signal difficult to detect and extremely difficult to monitor or jam. AN/PSC-3 Backpack radio set AN/PSC-3 is a portable, battery-powered, half-duplex uhf transceiver operat- ing in the 225.0- to 399.995-MHz range. It provides two-way voice (secure and plain) and data com- munications via satellite relay (SAT) or line-of-sight (los) modes. Radio set AN/PSC-3 components are shown in figure 2-26. One important feature of the AN/PSC-3 is its ability to interface directly with the AN/PRC-70, AN/PRC-77, and other vhf-capable radios, which provides a satellite link for vhf tactical equipment. This provides away to retransmit vhf information from one of these radios by (1) converting vhf to uhf, (2) transmitting through a satellite to another AN/PRC-3, (3) demodulating it and passing it directly to another Figure 2-26.—Radio Set AN/PSC-3. 2-28 AN/PRC-70/77, which could then (4) retransmit the information as vhf. This greatly enhances com- munications capability and extends the com- munications range. A basic retransmission setup is shown in figure 2-27. DIGITAL MESSAGE DEVICE GROUP (DMDG) The DMDG is part of the Special Forces Burst Communications System. It is used with radio sets AN/PRC-70/74 and AN/PSC-3 to send and receive messages. Messages are typed on the KY-879/P keyboard (shown in figure 2-28), which displays the message as it is being typed and stored in memory. When the message is ready to be sent, the operator selects the proper mode and the device converts the message to digital information. The digital in- formation is sent to one of the above radios for transmission. After the information is received at the other end, it is sent to another KY-879/P, where the message can be read on the device’s display screen. The device can send messages at 300 or 1200 baud in the satellite mode and 266.6 baud when connected to the AN/PRC-70/74. INTRODUCTION TO COMMUNICATIONS LINK INTERFACE PLANNING SYSTEM (CLIPS) The Communications Link Interface Planning System (CLIPS) was introduced to the Joint Special Operations Community in 1986. CLIPS is a system designed to help the communications planner Figure 2-27.—Basic retransmission scheme.