CHAPTER 3 SATELLITE COMMUNICATIONS

CHAPTER 3 SATELLITE COMMUNICATIONS INTRODUCTION In the past, the Navy relied upon hf communications as its primacy method of sending messages. With the overcrowding of the hf spectrum, the need for new and advanced long-range communications became apparent. Satellite communications (SATCOM) systems have shown they can provide survivable, reliable, high-capacity, secure, and cost-effective telecommunications for the military. In this chapter, you will be introduced to satellite communications fundamentals, fleet SATCOM sub- systems, shore terminals, current and future satellites, and some specific SATCOM equipment and racks. SATCOM is a natural outgrowth of modern technology and the continuing demand for greater capacity and high-quality communications. This information will be crucial to you in understanding the communications technology of both today and the future. After completing this chapter, you should be able to: Recognize satellite communications fundamentals Identify fleet SATCOM subsystems and shore terminals Evaluate specific SATCOM equipment and racks SATELLITE COMMUNICATIONS FUNDAMENTALS (A passive satellite simply reflects radio signals back to earth.) One station transmits to the satellite on the uplink frequency. The satellite translates the signal to the downlink frequency, amplifies the signal, then transmits it to the receiving terminal. Figure 3-1 shows A typical SATCOM link uses an active satellite that receives and retransmits, and two earth terminals. Figure 3-1.—Satellite communications system. 3-1