frequency hopping, no single carrier is used. Instead,the transmitter hops around the band in a randompattern, spending only a few milliseconds on any onefrequency. This makes the signal difficult to detect andextremely difficult to monitor or jam.AN/PSC-3Backpack 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 providestwo-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 areshown in figure 2-26.One important feature of the AN/PSC-3 is itsability to interface directly with the AN/PRC-70,AN/PRC-77, and other vhf-capable radios, whichprovides a satellite link for vhf tactical equipment.This provides away to retransmit vhf information fromone 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 anotherFigure 2-26.—Radio Set AN/PSC-3.2-28AN/PRC-70/77, which could then (4) retransmit theinformation as vhf. This greatly enhances com-munications capability and extends the com-munications range. A basic retransmission setup isshown in figure 2-27.DIGITAL MESSAGE DEVICE GROUP(DMDG)The DMDG is part of the Special Forces BurstCommunications System. It is used with radio setsAN/PRC-70/74 and AN/PSC-3 to send and receivemessages. Messages are typed on the KY-879/Pkeyboard (shown in figure 2-28), which displays themessage as it is being typed and stored in memory.When the message is ready to be sent, the operatorselects the proper mode and the device converts themessage to digital information. The digital in-formation is sent to one of the above radios fortransmission. After the information is received at theother end, it is sent to another KY-879/P, where themessage can be read on the device’s display screen.The device can send messages at 300 or 1200 baudin the satellite mode and 266.6 baud when connected tothe AN/PRC-70/74.INTRODUCTION TOCOMMUNICATIONS LINKINTERFACE PLANNING SYSTEM(CLIPS)The Communications Link Interface PlanningSystem (CLIPS) was introduced to the Joint SpecialOperations Community in 1986. CLIPS is a systemdesigned to help the communications plannerFigure 2-27.—Basic retransmission scheme.
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