transmitted, type of modulation (AM, FM, or PM or a hybrid), where in the fre- quency spectrum (see Figure 2.6) in which transmission is to be affected, and licensing restrictions. Figure 2.14 is a generalized model of a radio link. The information transport capacity of a radio link depends on many factors. The first factor is the application. The following is a brief list of applications with some relevant RF bandwidths: Line-of-sight microwave, depending on the frequency band: 2, 5, 10, 20, 30, 40, 60 MHz. SCADA (system control and data acquisition): up to 12 kHz in the 900-MHz band. 6In the context of this book, "high-frequency" takes on the connotation of any signal from 400 MHz to 100 GHz. 2.5 INTRODUCTION TO TRANSPORTING ELECTRICAL SIGNALS Antenna Transmitter Information baseband Modulator exciter converter Synthesizer Receiver Antenna Recovered baseband converter modulator Synthesizer Intermediate frequency A synthesizer is a stable frequency source Power amplifier with variable discrete outputs. LNA = Low-noise amplifier Figure 2.14 A generic model of a typical radio link. Satellite communications, geostationary satellites: 500 MHz or 2.5-GHz bandwidths broken down into 36- and 72-MHz segments. Cellular radio: 25-MHz bandwidth in the 800/900-MHz band. The 25-MHz band is split into two 12.5-MHz segments for two competitive providers. Personal communication services (PCS): 200-MHz band just below 2.0 GHz, broken down into various segments such as licensed and unlicensed users. Cellular/PCS by satellite (e.g., Iridium, Globalstar), 10.5-MHz bandwidth in the 1600-MHz band. Local multipoint distribution system (LMDS) in 28/38-GHz bands, 1.2-GHz band- width for CATV, Internet, data, and telephony services (Ref. 5). Bandwidth is also determined by the regulating authority (e.g., the FCC in the United States) for a particular service/application. Through bit packing techniques, described in Chapter 9, the information carrying capacity of a unit of bandwidth is considerably greater than 1 bit per Hz of bandwidth. 