Notes for EECS 120, Sp 2002

Home , Alfred Vail, Radio Act of 1912

Pravin Varaiya

January 27, 2002 Chapter 1

Communication system

Transmitter Receiver

m x x y m power T R ym y modulator channel amplifier demodulator amplifier

received source carrier modulated transmitted received baseband baseband signal, signal signal signal signal signal 2πω t e c channel ω |M(ω)| |XT( )|

ω ω −ω ω c c

Figure 1.1: Basic components of a communication system.

Figure 1.1 indicates the basic components of a communication system. The source signal m ∈ ContSignals is a baseband signal. The modulator transforms this signal into the signal xm ∈ ContSignals whose frequency spectrum is centered around the carrier frequency ωc rad/sec. The power amplifier boosts the amplitude of xm to a level sufficient for transmission. The transmitted signal xT propagates through the channel. The output of the channel is the received signal yR. The receiver amplifies this signal to ym. The demodulator processes it and the final received signal is y. A well-designed communication system should have y ≈ m. The FCC assigns a particular part of the electromagnetic spectrum—called a channel—to each station. The modulator transforms the baseband signal x into the signal xm whose spectrum Xm fits inside the station’s channel, as shown in the lower part of the figure. For example, the AM station KCBS is assigned the 10 kHz-wide channel, 740 ± 5 kHz, while the FM station KQED is assigned the 200 kHz-wide channel 88.5 ± 0.1 MHz. KRON TV is assigned the 6 MHz-wide channel, 66-72 MHz, called channel # 4.

3 4 CHAPTER 1. COMMUNICATION SYSTEM

The FCC also assigns a portion of the spectrum to each cellphone company, e.g., Cingular, Verizon, ATT wireless. That spectrum is shared by the carrier’s subscribers when they make a call.

1.1 Radio, TV and cellular phones

The FCC imposes standards on AM and FM broadcast radio, and broadcast TV. AM channels are 10 kHz wide, FM channels are 200 kHz wide, broadcast TV channels are 6 MHz wide. Some features of the standards are shown in Tables 1.1 and 1.2. The oldest cellular telephone system is AMPS, described in Table 1.3. In the AMPS system, the carrier uses a modulation scheme to divide its assigned spectrum among a number of 30 kHz-wide channels. A voice connection between a mobile and the base station occupies two 30 kHz channels, one for uplink, the other for downlink. The voice signal is modulated at the mobile and at the base station so that the modulated signal ﬁts in the assigned channel. Digital control channels are used by the mobile to request the base station for a voice channel and by the base station to assign a voice channel. The voice signal in AMPS is analog. Newer cellular systems digitize voice, and the voice channels are narrower than 30 kHz. As a result, newer systems can carry a larger number of voice calls in the same spectrum as the AMPS system. One says that the newer systems have greater spectral efﬁciency than AMPS. Appendix 1 is a chart that shows the FCC’s allocation of the radio spectrum (3 kHzÐ300 GHz) to different uses. The chart in Appendix 2 focuses on wireless radio. Appendix 3 is a primer on the electromagnetic spectrum. Appendix 4 is a brief history of the telegraph and broadcast media. 1.1. RADIO, TV AND CELLULAR PHONES 5

Item Description Assigned frequency, fc In 10-kHz increments from 540 to 1700 kHz Channel bandwidth 10 kHz Carrier frequency stability ±20 Hz % modulation Maintain 85-95%; max: 100% neg; 125% pos Noise and carrier hum At least 45 db below 100% modulation in the band 30 Hz to 20 Hz Max power licensed 50 kW

Table 1.1: FCC restrictions on AM broadcast radio.

Item Description Assigned frequency, fc In 200-kHz increments from 88.1 MHz to 107.9 MHz Channel bandwidth 200 kHz Carrier frequency stability ±200 Hz 100% modulation ∆F =75kHz Modulation index 5 (∆F =75kHz,B = 200kHz) FM noise At least 60 db below 100% modulation at 400 Hz Max power licensed 100 kW

Table 1.2: FCC restrictions on FM broadcast radio.

Item Description Channel bandwidth 6 MHz Visual carrier frequency 1.25 MHz ±1000 Hz above lower boundary of channel Aural carrier frequency 4.5 MHz ±1000 Hz above visual carrier Chrominance subcarrier fre- 3.579545 MHz ±10 Hz quency Aspect ratio (width-to-height) 4:3 Modulation visual AM with negative polarity, i.e. decrease in light level causes increases in amplitude Aural modulation FM with 100% modulation being ∆F =25kHz.

Table 1.3: FCC restrictions on broadcast TV. 6 CHAPTER 1. COMMUNICATION SYSTEM

Item Description Base station transmit bands 869Ð896 MHz Mobile transmit bands 824Ð851 Mobile max power 3 Watts Channel bandwidth 30 kHz Voice modulation FM, 12-kHz peak deviation Control channel FSK, 8-kHz peak deviation, 10 kbps

Table 1.4: AMPS cellular telephone.

1.2 Channel models

The transmitted signal xT is an electromagnetic wave, which propagates or travels through the channel at the speed of light. The received signal is xR. See ﬁgure 1.1. A channel has three forms of propagation media, free space, copper, and optical ﬁber (glass):

• Broadcast signals (radio, TV, cellphone) are transmitted freely through space;

• Point-to-point transmission is over copper (twisted pair local loop or CATV coax cable) or optical ﬁber (high-speed Ethernet or long-distance telephony)

As the signal propagates through a channel, it degrades through attenuation, dispersion, noise.

Attenuation

xT yR

channel transmit receive power power p pT R

Figure 1.2: The signal is attenuated as it propagates through the channel

In free space the attenuation is PR c 2 = GT ( ) GR, (1.1) PT 4πfd 5 where GT ,GR are the transmit and receive antenna gains, c =3× 10 km/s is the speed of light, d km is the distance between transmitter and receiver, and f Hz is the carrier frequency. It is standard in communications and control to express power and attenuation in db (decibels). (P Watts equals 10 log10 P db.) So, taking GT = GR =1for illustration, the free space attenuation is 5 PR 3 × 10 10 log10 =20log10 . (1.2) PT 4πfd 1.2. CHANNEL MODELS 7

Thus attenuation gets worse as f and d increase. A ten-fold increase in f or d decreases attenuation by 20 db.

Example 1.1: At a distance of 10 km, the attenuation for KCBS-AM with f = 740 kHz is 3 × 105 20 log10 ≈−50 db. 4π × 740 × 103 × 10 For KQED-FM, also at d =10km, but f =88.5 MHz, nearly 100 times the carrier frequency of KCBS, the attenuation will be 1002 or 40 db worse, 3 × 105 20 log10 ≈−90 db. 4π × 88.5 × 106 × 10 For a PCS cellphone in the 2 GHz band, if the distance between the base station and mobile is 1 km, the attenuation is 3 × 105 20 log10 ≈−100 db. 4π × 2 × 109

When the signal is transferred over a waveguide, like coax cable or optical ﬁber, the signal is con- ﬁned to the waveguide, and attenuation is caused by power dissipation in the medium. So attenuation is expressed in db/km.

Example 1.2: For one coax cable (LMR-195), the attenuation is given in the following table. Frequency (MHz) 1 10 100 1000 Attenuation (db/km) -12 -37 -118 -385

By contrast, the attenuation of light in single-mode optical ﬁber is -0.2 db/km for wavelengths near 1.55 µm.

To explore the consequences of attenuation, refer again to ﬁgure1.1. The received power PR must exceed a minimum level so that the demodulated signal y is close to the original signal x. This minimum level is called the receiver sensitivity. For illustration suppose your FM radio receiver sensitivity is -50 db or 10 µW. The transmit power of KQED-FM is 100,000 W or 50 db. Thus your radio can receive the KQED broadcast at a distance of d km if PR 10 log10 = −100 = −70 − 20 log10 d, PT or d ≈ 14 km.

For optical receivers the sensitivity is -75 db (0.03 µW). The laser transmit power is small, PT = −30 db (1 mW). So the maximum distance d of the optical ﬁber (with attenuation of -0.2 db/km) is

10 log10 PR − 10 log10 PT = −0.2d, so −75 + 30 = −0.2d or d = 225 km. Thus signals can travel through optical ﬁber for 225 km before they need to be ampliﬁed. 8 CHAPTER 1. COMMUNICATION SYSTEM

Dispersion

Σ δ y Σ xT = a(n) (t-nT) R = a(n)h(t-nT)

nT channel

Figure 1.3: The sequence of impulses xT is spread out by the channel. If T is too small, the responses of the impulses overlap and lead to errors.

Dispersion is best appreciated in the context of digital communication. Suppose a binary signal a : Integers →{0, 1} is encoded into a sequence of very narrow pulses T seconds apart. Ideally these pulses are δ functions, so ∞ ∀t ∈ Reals,xT (t)= a(n)δ(t − nT ). n=−∞

Thus a ‘1’ is encoded into the presence of an impulse and a ‘0’ into the absence of an impulse. The channel is an LTI system with impulse response h so the received signal is ∞ ∀t ∈ Reals,yT (t)= a(n)h(t − nT ). n=−∞

Typically, h is spread out or dispersed as shown in ﬁgure1.3, and the response to adjacent δ functions will overlap if T is very small. The smaller is T , i.e. the larger is the bit rate 1/T , the larger is the overlap. This overlap is called inter-symbol interference. If the overlap is too great, the receiver will make an error in detecting whether an impulse is present or absent. Thus dispersion places a limit on the bit rate. See exercise ??. As we will see, dispersion can be partially compensated by equalization.

Noise

The third source of signal degradation is noise. Noise may arise from the channel itself or from the receiver amplifier. In broadcast channels, noise may arise from other broadcast signals that are in the same frequency band (this is called co-channel interference and is common in cellular phones), or from reflection and scattering. In copper wires noise may arise from electromagnetic radiation from adjacent wires (this is called cross-talk). The receiver amplifier always produces noise called thermal noise. The effect of noise is mitigated by appropriate filtering. 30 59 61 70 90 110 130 160 190 200 275 285 300 3 9 14 19.95 20.05 30

Fixed MARITIME MARITIME MOBILE FIXED MARITIME MOBILE MARITIME Maritime

MARITIME MOBILE Aeronautical Radionavigation FIXED (Radio Beacons) MOBILE MOBILE

Mobile Aeronautical Radionavigation (Radio Beacons) TIME SIGNAL (20 kHz) TIME NOT ALLOCATED RADIONAVIGATION FIXED SIGNAL (60 kHz) TIME Radiolocation RADIONAVIGATION Radiolocation Mobile AND AND UNITED Aeronautical

MARITIME AERONAUTICAL AERONAUTICAL FIXED FIXED FIXED MARITIME FIXED RADIONAVIGATION MARITIME MOBILE FIXED MOBILE RADIONAVIGATION MARITIME (RADIO BEACONS)

MOBILE RADIONAVIGATION STANDARD FREQ. STANDARD STANDARD FREQ. STANDARD AERONAUTICAL RADIONAVIGATION 3 kHz 300 kHz 1605 1615 1625 1705 1800 1900 2000 2065 2107 2170 2173.5 2190.5 2194 2495 2501 2502 2505 2850 3000 300 325 335 405 415 435 495 505 510 525 535

MARITIME MARITIME

Aeronautical MOBILE MOBILE MOBILE

AERONAUTICAL FIXED MARITIME MOBILE

Aeronautical MARITIME

Radionavigation RADIONAVIGATION VIGATION (2500kHz)

AERONAUTICAL Radionavigation (RADIO BEACONS) (Radio Beacons) RADIONAVIGATION (RADIO BEACONS) Space Research MOBILE LAND MOBILE LAND MOBILE AERONAUTICAL MARITIME (RADIO BEACONS) BROADCASTING RADIONA BROADCASTING BROADCASTING LAND MOBILE RADIONAVIGATION

STATES AERONAUTICAL (RADIO BEACONS) RADIONAVIGATION BROADCASTING MOBILE FIXED Mobile (AM RADIO) AMATEUR MOBILE (R) Aeronautical MOBILE MOBILE AERONAUTICAL RADIOLOCATION

MARITIME MOBILE Aeronautical MARITIME MOBILE RADIONAVIGATION MARITIME MARITIME MOBILE (TELEPHONY) MARITIME MOBILE (TELEPHONY) Mobile MARITIME MOBILE (TELEPHONY)

MOBILE AND CALLING) MOBILE (DISTRESS (RADIO BEACONS) RADIO- AND TIME SIGNAL FREQ. STANDARD MOBILE MOBILE MOBILE MARITIME Radiolocation Radiolocation

MOBILE (DISTRESS AND CALLING) LOCATION STANDARD FREQ. STANDARD STANDARD FREQ. AND TIME SIGNAL AND TIME SIGNAL FREQ. STANDARD (SHIPS ONLY) MOBILE

Maritime FIXED FIXED Aeronautical Mobile AERONAUTICAL FIXED RADIONAVIGATION Radionavigation (Radio Beacons)

TRAVELERS INFORMATION SERVICE AT 1610 kHz FREQUENCY 300 kHz 3 MHz 3.0 3.025 3.155 3.230 3.4 3.5 4.0 4.063 4.438 4.65 4.7 4.75 4.85 4.995 5.003 5.005 5.060 5.45 5.68 5.73 5.95 6.2 6.525 6.685 6.765 7.0 7.1 7.3 8.1 8.195 8.815 8.965 9.040 9.5 9.9 9.995 10.003 10.005 10.1 10.15 11.175 11.275 11.4 11.65 12.05 12.23 13.2 13.26 13.36 13.41 13.6 13.8 14.0 14.25 14.35 14.990 15.005 15.010 15.10 15.6 16.36 17.41 17.55 17.9 17.97 18.03 18.068 18.168 18.78 18.9 19.68 19.80 19.990 19.995 20.005 20.010 21.0 21.45 21.85 21.924 22.0 22.855 23.0 23.2 23.35 24.89 24.99 25.005 25.01 25.07 25.21 25.33 25.55 25.67 26.1 26.175 26.48 26.95 26.96 27.23 27.41 27.54 28.0 29.7 29.8 29.89 29.91 30.0

FIXED FIXED FIXED FIXED (5000 KHZ) Mobile Mobile* Mobile* Mobile* (15,000 kHz) FIXED (25,000 kHz) FIXED (10,000 kHz) Mobile* MOBILE FIXED FIXED MOBILE FIXED MOBILE** MOBILE** FIXED FIXED MOBILE FIXED AMATEUR AMATEUR MOBILE** MOBILE** Space Research TEUR SATELLITE Space Research Space Research Space Research Space Research Space Research NAL (20,000 KHZ) NAL AMATEUR SATELLITE AMATEUR AMATEUR SATELLITE AMATEUR AMATEUR SATELLITE AMATEUR MARITIME MARITIME FIXED MARITIME FIXED MARITIME MOBILE** AMATEUR MOBILE MOBILE FIXED

MOBILE FIXED

MOBILE ASTRONOMY FIXED FIXED FIXED FIXED FIXED FIXED FIXED FIXED FIXED FIXED FIXED . AMATEUR MOBILE** MOBILE (R) AMATEUR MOBILE (OR) LAND MOBILE AMATEUR LAND MOBILE AERONAUTICAL LAND MOBILE AERONAUTICAL LAND MOBILE LAND MOBILE BROADCASTING BROADCASTING BROADCASTING BROADCASTING MARITIME MOBILE MARITIME MOBILE MARITIME MOBILE MARITIME MOBILE

ALLOCATIONS MARITIME MOBILE RADIO RADIO ASTRONOMY RADIO BROADCASTING BROADCASTING BROADCASTING BROADCASTING TIME SIG MARITIME MOBILE AERONAUTICAL MOBILE (R) AERONAUTICAL MOBILE (R) AERONAUTICAL MOBILE (R) AERONAUTICAL MOBILE (R) AERONAUTICAL MOBILE (R) AERONAUTICAL MOBILE (R) AERONAUTICAL MOBILE (R) AERONAUTICAL MOBILE (OR) AERONAUTICAL MOBILE (OR) AERONAUTICAL MOBILE (OR) AERONAUTICAL MOBILE (OR) AERONAUTICAL MOBILE (OR) AERONAUTICAL MOBILE (OR) AERONAUTICAL MOBILE (OR) AERONAUTICAL MOBILE (OR) MOBILE** Mobile Mobile* AERONAUTICAL MOBILE (OR) FIXED FIXED FIXED FIXED FIXED Mobile FIXED Mobile FIXED FIXED FIXED FIXED Radio- MOBILE* AMATEUR AMATEUR AMA AERONAUTICAL MOBILE (R) AMATEUR AMATEUR FIXED FIXED AERONAUTICAL MOBILE (R) MOBILE* MOBILE* MOBILE* AERONAUTICAL MOBILE (R) STANDARD FREQUENCY & FREQUENCY& TIME SIG STANDARD STANDARD FREQ. AND TIME STANDARD SIGNAL

location FREQ. STANDARD MARITIME MOBILE STANDARD FREQ. STANDARD STANDARD FREQ. STANDARD STANDARD FREQ. STANDARD STANDARD FREQ. STANDARD STANDARD FREQ. AND TIME STANDARD SIGNAL STANDARD FREQ. AND TIME STANDARD SIGNAL STANDARD FREQ. AND TIME STANDARD SIGNAL AMATEUR SATELLITE AMATEUR STAND. FREQ. & STAND. AMATEUR SATELLITE AMATEUR MARITIME MOBILE

ISM – 6.78 ± .015 MHz ISM – 13.560 ± .007 MHz ISM – 27.12 ± .163 MHz THE RADIO SPECTRUM 3 MHz 30 MHz 72.0 73.0 74.6 74.8 75.2 75.4 76.0 88.0 108.0 117.975 121.9375 123.0875 123.5875 128.8125 132.0125 136.0 137.0 137.025 137.175 137.825 138.0 144.0 146.0 148.0 149.9 150.05 150.8 156.2475 157.0375 157.1875 157.45 161.575 161.625 161.775 162.0125 173.2 173.4 174.0 216.0 220.0 222.0 225.0 235.0 300 30.0 30.56 32.0 33.0 34.0 35.0 36.0 37.0 37.5 38.0 38.25 39.0 40.0 42.0 46.6 47.0 49.6 50.0 54.0 T. (S-E) T. (S-E) T. (S-E) T. (S-E) T. Amateur

MOBILE (R) MOBILE TELLITE MET. SA MET. SA MET. SA MET. SA MET. AERONAUTICAL MOBILE RADIO SERVICES COLOR LEGEND MOBILE MOBILE MOBILE MOBILE MOBILE MOBILE MOBILE MOBILE Radio- Land Mobile location MOBILE MOBILE MOBILE MOBILE MOBILE MOBILE MOBILE MOBILE MOBILE MOBILE LAND MOBILE AMATEUR SA AMATEUR

AERONAUTICAL Radiolocation MOBILE SATELLITE (E-S) MOBILE SATELLITE Radiolocation INTER-SATELLITE RADIO ASTRONOMY LAND LAND LAND LAND LAND BROADCASTING BROADCASTING BROADCASTING AERONAUTICAL (S-E) BROADCASTING SPACE OPN. (S-E) SPACE OPN. (S-E) SPACE MOBILE OPN. (S-E) SPACE OPN. (S-E) SPACE Land Space Operations Mobile MOBILE MOBILE MOBILE FIXED MOBILE MOBILE AMATEUR (TV CHANNELS 2-4) (TV CHANNELS 5-6) (FM RADIO) RADIONAVIGATION (TV CHANNELS 7-13) MOBILE SATELLITE FIXED ASTRONOMY AMATEUR LAND MOBILE LAND MOBILE LAND MOBILE MARITIME MOBILE MARITIME MOBILE MOBILE (R) MARITIME MOBILE MARITIME MOBILE MARITIME MOBILE MOBILE (R) MOBILE (R) Fixed LAND MOBILE LAND MOBILE (S-E) AERONAUTICAL AERONAUTICAL AERONAUTICAL SPACE RES. (S-E) SPACE RES. (S-E) SPACE SPACE RES. (S-E) SPACE RES. (S-E) SPACE Met. Satellite FIXED FIXED FIXED RADIO AERONAUTICAL RADIODETERMINATION TION SATELLITE FIXED FIXED FIXED FIXED FIXED AERONAUTICAL MOBILE AERONAUTICAL MOBILE Astronomy Mobile FIXED FIXED FIXED FIXED FIXED FIXED FIXED FIXED AMATEUR FIXED

LAND MOBILE FIXED VIGA AERONAUTICAL MOBILE (R) MOBILE SATELLITE SATELLITE Aeronautical FIXED ASTRONOMY (S-E) AMATEUR AERONAUTICAL RADIONAVIGATION AERONAUTICAL Radio RADIONA Mob. Sat. (S-E) Mob. Sat. (S-E) MOB. SAT. (S-E) MOB. SAT. (S-E) MOB. SAT. Space Research MOBILE MOBILE SATELLITE (E-S) MOBILE SATELLITE LAND MOBILE MARITIME RADIO

AERONAUTICAL LAND MOBILE RADIOLOCATION ISM – 40.68 ± .02 MHz 137-139 SPACE RESEARCH (SPACE TO EARTH) RADIONAVIGATION SATELLITE 30 MHz 300 MHz 1990 2110 2150 2160 2200 2290 2300 2310 2360 2390 2400 2402 2417 2450 2483.5 2500 2655 2690 2700 2900 3000 300.0 322.0 328.6 335.4 399.9 400.05 400.15 401.0 402.0 403.0 406.0 406.1 410.0 420.0 450.0 460.0 470.0 512.0 608.0 614.0 806 890 902 928 929 932 935 940 941 944 960 1215 1240 1300 1350 1390 1400 1427 1429 1432 1435 1530 1535 1544 1545 1549.5 1558.5 1559 1610 1610.6 1613.8 1626.5 1645.5 1646.5 1651 1660 1660.5 1668.4 1670 1675 1700 1710 1755 1850 TLC) TLC) TLC) †† (1999) AMATEUR MARITIME MOBILE RADIOLOCATION SATELLITE † (S-E) . (s-E)(s-s) EARTH FIXED MET. SAT. MET. Fixed Land Mobile (TLM & . (R) (E-S)

MOBILE S) MOBILE SAT Radiolocation EXPLORATION Fixed Mobile Mobile Sat. (S-E) (E-S) (S-E) Earth Expl. EARTH SPACE RADIO ASTRONOMY

Amateur BROADCASTING (Aero. TLM) (Passive) Satellite (E-S) SATELLITE Land Mobile (TLM & Land Mobile (TLM & MOBILE RESEARCH MOBILE** (1999/2004) SAT. (Passive) SAT. Radiolocation EXPLORATION Amateur MOBILE SAT. (S-E) MOBILE SAT. †† BROADCASTING Space Research (TV CHANNELS 14-20) Fixed Amateur Amateur FIXED RADIOLOCATION Earth Expl. Satellite MOBILE RADIOLOCATION RADIOLOCATION MOBILE MOBILE MOBILE (Space to Earth) T. (E-S) T. T. (E-S) T. (E-S) ) Mobile Satellite (E-s) BROAD- SPACE MOBILE SATELLITE CASTING Mobile Satellite (S- E) Radiolocation SATELLITE (s-E)(s-s) Satellite (S-E) Radiolocation Meteorological MOBILE SATELLITE (S-E) MOBILE SATELLITE OPERATION MOBILE SATELLITE (R) (E-s) SATELLITE MOBILE (S-E AIDS (Radiosonde) METEOROLOGICAL METEOROLOGICAL MOBILE SATELLITE (E-s) MOBILE SATELLITE (E-S) . METEOROLOGICAL RADIOLOCATION AIDS (Radiosonde) Space Opn. MOBILE SATELLITE (S-E) MOBILE SATELLITE TION AIDS (RADIOSONDE) Fixed (TLM) Fixed (TLM) . (E-S) MOBILE SATELLITE (E-S) MOBILE SATELLITE AERO. MOBILE SAT MOBILE MOBILE SA MOBILE SA MARITIME MOBILE RESEARCH (Passive) SPACE RADIONAV. SATELLITE (Space to Earth) SATELLITE RADIONAV. Met. Satellite

BROADCASTING BROADCASTING LAND MOBILE AERONAUTICAL (1999) FIXED # FIXED

MOBILE Fixed

MOBILE † METEOROLOGICAL AMATEUR SATELLITE RADIONAVIGATION . SAT FIXED (1999) MOBILE**

(TV CHANNELS 21-36) (TV CHANNELS 38-69) RADIONAVIGATION SPACE (E-S) (E-S) SATELLITE SATELLITE FIXED AIDS SATELLITE EARTH (s-E)(s-s) FIXED (Passive) FIXED MOBILE SAT FIXED FIXED FIXED FIXED Amateur Space RESEARCH (S-E) MOBILE (Space to Earth) MOBILE MOBILE Amateur MOBILE (1999) MOBILE AMATEUR (Passive) Satellite (E-S) Research AMATEUR Meteorological †† † MOBILE EXPLORATION SPACE RES. SPACE RADIOLOCA RADIO DET Radio- SPACE RESEARCH SPACE location VIGATION LAND MOBILE SATELLITE (Passive) SATELLITE LAND MOBILE LAND MOBILE TIME SIGNAL SAT. (400.1 MHz) SAT. TIME SIGNAL MOBILE . RADIO ASTRONOMY FIXED SPACE OPN. SPACE MOBILE TION Space to Earth RADIO DET. SAT. SAT. RADIO DET. (LOS) MOBILE SATELLITE (E-S) MOBILE SATELLITE RADIO DET. SAT. SAT. RADIO DET. MOBILE Radio MOBILE SATELLITE (S-E) MOBILE SATELLITE

MOBILE SATELLITE MOBILE SATELLITE RADIOLOCATION LAND MOBILE (1999/2004) VIGA MOBILE. SAT. (S-E) SAT. Astronomy ASTRONOMY ASTRONOMY FIXED MOBILE †† FIXED FIXED FIXED FIXED ASTRONOMY MET. SAT. AERONAUTICAL (space to Earth) (space to Earth) (1999) (space to Earth) Radiolocation MARITIME † FIXED SATELLITE FIXED (1999) MARITIME RADIONAVIGATION AIDS . (AERONAUTICAL TELEMETERING) (AERONAUTICAL SATELLITE (s-E) SATELLITE †

BROADCASTING RADIO AERONAUTICAL RADIONAVIGATION AERONAUTICAL (s-E) RADIONAVIGATION METEOROLOGICAL FIXED METEOROLOGICAL AIDS METEOROLOGICAL (RADIOSONDE) FIXED SATELLITE (s-E) SATELLITE FIXED AERONAUTICAL MOBILE SATELLITE (R) (space to Earth) AERONAUTICAL MOBILE SATELLITE RADIO FIXED BROADCASTING Mobile LAND MOBILE RADIO RADIO RADIO METEOROLOGICAL SATELLITE (S-E) SATELLITE MARITIME MOBILE SATELLITE MET

(Space to Earth) MOBILE . AIDS . AERONAUTICAL FIXED Sat. RADIONAVIGATION ASTRONOMY (LOS) RADIOLOCATION RADIOLOCATION FIXED FIXED (Radiosonde) STD. FREQ. & Earth RADIONAVIGATION SATELLITE RADIONAVIGATION SPACE AERONAUTICAL RADIONA AERONAUTICAL SPACE RESEARCH SPACE RADIONAVIGATION MET. AIDS MET. RADIO MET FIXED AERONAUTICAL MOBILE SATELLITE (R) MOBILE SATELLITE AERONAUTICAL AERONAUTICAL MOBILE SATELLITE (R) MOBILE SATELLITE AERONAUTICAL ASTRONOMY (Passive) RADIONAVIGATION SATELLITE RADIONAVIGATION AERO. RADIONA AERO. RADIONAV. MARITIME MOBILE SAT (Radiosonde) ASTRONOMY (Radiosonde) AERO. RADIONAV. MARITIME MOBILE SATELLITE (E-s) RADIODETERMINATION SAT. (S-E) SAT. RADIODETERMINATION (E-S) (1999) (s-E) (deep space only) OPERATION Exploration AERONAUTICAL MOBILE SATELLITE (R) (E-s) MOBILE SATELLITE AERONAUTICAL (R) (E-s) MOBILE SATELLITE AERONAUTICAL

ISM – 915.0 ± 13 MHz 1850-1910 AND 1930-1990 MHz ARE ALLOCA TED TO PCS; 1910-1930 MHz ISM – 2450.0 ± 50 MHz BROADCASTING METEOROLOGICAL IS DESIGNATED FOR UNLICENSED PCS DEVICES SPACE OPERATION SATELLITE AIDS 300 MHz 3 GHz 3.0 3.1 3.3 3.5 3.6 3.65 3.7 4.2 4.4 4.5 4.66 4.685 4.8 4.99 5.0 5.25 5.35 5.46 5.47 5.6 5.65 5.85 5.925 6.425 6.525 6.875 7.075 7.125 7.19 7.235 7.25 7.30 7.45 7.55 7.75 7.90 8.025 8.175 8.215 8.4 8.45 8.5 9.0 9.2 9.3 9.5 10.0 10.45 10.5 10.55 10.6 10.68 10.7 11.7 12.2 12.7 12.75 13.25 13.4 14.0 14.2 14.4 14.5 14.7145 15.1365 15.35 15.4 15.7 16.6 17.1 17.2 17.3 17.7 17.8 18.6 18.8 19.7 20.2 21.2 21.4 22.0 22.21 22.5 22.55 23.0 23.55 23.6 24.0 24.05 24.25 25.25 27.0 27.5 29.5 30.0 *

TION FIXED Mobile EARTH EXPLORATION METEOROLOGICAL MOBILE Radio- Radio- location location Radio- FIXED Mobile Radio- Mobile Radio- location (no airborne)

FIXED FIXED Satellite (E-S) location SATELLITE SPACE RESEARCH Amateur location

MOBILE EXPL. EARTH (Passive) SAT. MOBILE

Radio- FIXED Land Mobile location Land Mobile Fixed Satellite (E-S) (S-E) Mobile Radio- Fixed FIXED FIXED Space Radio- EARTH EXPL. EARTH (Passive) SAT. Mobile Satellite Satellite (E-S) location Satellite (E-S) Satellite (S-E) MOBILE FIXED location FIXED (S-E) (Passive)

SATELLITE Satellite Amateur SATELLITE FIXED FIXED FIXED Research MOBILE (E-S)(no airborne) Radiolocation SATELLITE MOBILE MOBILE Amateur Amateur EARTH EXPL. EARTH SATELLITE (E-S) SATELLITE

SATELLITE TELLITE (E-S)

SATELLITE SATELLITE RADIOLOCA SATELLITE Satellite (S-E) Radiolocation FIXED SAT. (Passive) SAT. Space Research Space Research . EARTH EXPL. EARTH FIXED . FIXED SATELLITE (Passive) SATELLITE Radiolocation FIXED EARTH EXPL. SAT. MOBILE MOBILE MOBILE (E-S) MOBILE (S-E) (S-E) Amateur Mobile Satellite (S-E) MOBILE MOBILE FIXED INTER-SATELLITE MOBILE* * MET. (E-S) Radiolocation (S-E) INTER-SATELLITE SPACE Radiolocation Radiolocation VIGATION (Passive) Radiolocation Radiolocation TION Radiolocation Radiolocation Radiolocation SATELLITE TION (deep space only) Radiolocation Radiolocation Radiolocation RESEARCH SATELLITE (S-E) SATELLITE (S-E) FIXED (S-E) Space Research (E-S) FIXED FIXED RADIO- N Amateur FIXED FIXED FIXED AMATEUR SATELLITE AMATEUR RADIO RADIO- FIXED SAT SAT. (E-S) SAT. SPACE RESEARCH (S-E) SPACE (Passive) MOBILE FIXED SAT SAT. (E-S) SAT. LOCA Space Research (Passive) LOCA SPACE RESEARCH (E-S) SPACE MOBILE SA Land Mobile Satellite (E-S) SPACE RES. SPACE Radiolocation ASTRONOMY STANDARD FREQUENCY TION FIXED MOBILE (S-E) AIDS RADIO Aids FIXED FIXED FIXED -E) FIXED SPACE FIXED Fixed FIXED FIXED FIXED FIXED Amateur MOBILE FIXED FIXED FIXED Mobile FIXED Mobile FIXED

FIXED MOBILE

MOBILE (Passive) MOBILE RADIO- MOBILE MOBILE RADIO- (Passive) SAT. (S-E) SAT. ASTRONOMY MOBILE MOBILE MOBILE SATELLITE Radiolocation LOCA LOCATIO SPACE RES. SPACE Meteorological

AND TIME SIGNAL (S-E) SATELLITE (E-S) SATELLITE (S-E) SATELLITE TION TION METEOROLOGICAL FIXED SATELLITE (E-S) SATELLITE INTER-SATELLITE Space Research RESEARCH (Passive) SPACE RESEARCH SPACE SATELLITE (E-S) SATELLITE (E-S) MET. FIXED (E-S) (deep space) . (Passive) . AERONAUTICAL SATELLITE (Active) AERONAUTICAL RADIO- RADIOLOCATION Mobile RADIO SATELLITE Standard RADIO- RADIO- MOBILE Freq. and Space Res. EARTH EXPL. EARTH SAT Time Signal LOCATION RADIONAVIGATION Standard RADIONAVIGATION LOCA LOCA EARTH EXPL. Satellite (E-S) (E-S) Time Signal Time NAVIGATION FIXED SATELLITE(S FIXED (S-E) SATELLITE Mobile ** RADIO- FIXED Satellite (E-S) Frequency and SPACE

FIXED SATELLITE (Passive) MOBILE** RESEARCH FIXED FIXED FIXED MOBILE FIXED FIXED FIXED FIXED FIXED FIXED ASTRONOMY FIXED

LOCATION MOBILE FIXED AERONAUTICAL RADIONA AERONAUTICAL

RADIO- MARITIME AMATEUR VIGATION FIXED MARITIME . (E-S) (S-E)

SATELLITE SATELLITE MARITIME AERONAUTICAL ASTRONOMY FIXED FIXED FIXED SATELLITE (E-S) SATELLITE SATELLITE (E-S) SATELLITE FIXED FIXED FIXED RADIO RADIO (S-E) Earth

LOCATION FIXED FIXED RADIONAVIGATION RADIOLOCATION RADIONAVIGATION RADIO- FIXED (Ground) FIXED

STANDARD FREQUENCY MARITIME FIXED

MOBILE (S-E) MOBILE FIXED . (S-E) FIXED RADIO- RADIO- RADIO- Standard Space Space Fixed BROADCASTING SPACE (Passive) (S-S) LOCATION FIXED FIXED SATELLITE Earth Exploration RADIOLOCATION RADIOLOCATION RADIOLOCATION Time Signal Time RADIOLOCATION RADIOLOCATION RADIONAV. Research MOBILE SATELLITE Research RADIONAVIGATION LOCATION LOCATION RADIONAVIGATION SATELLITE Satellite LOCATION FIXED SATELLITE (E-S) FIXED SATELLITE ASTRONOMY . (Passive) FIXED SATELLITE (S-E) FIXED SATELLITE Earth Expl. Satellite (S-E) ASTRONOMY FIXED Satellite (S-S) Earth Expl. EARTH EXPL. EARTH SAT RADIONAVIGATION FIXED SATELLITE (E-S) FIXED SATELLITE AERONAUTICAL RADIONAV. RADIO NAV.(Ground) FIXED SATELLITE (E-S) FIXED SATELLITE (Deep Space) Frequency and SATELLITE (S-E) SATELLITE SATELLITE (E-S) SATELLITE RADIONA SPACE RESEARCH (S-E) SPACE NAV.(Ground) AERONAUTICAL Exploration AERO. RADIO- AERO. RADIO- SATELLITE (S-E) SATELLITE SATELLITE (E-S) SATELLITE AERONAUTICAL EARTH EXPL. EARTH SATELLITE (S-E) SATELLITE SPACE RESEARCH SPACE Satellite (Active) RADIONAVIGATION RADIO RADIONAVIGATION FIXED SATELLITE (S-E) FIXED SATELLITE SATELLITE (S-E) SATELLITE EARTH EXPL. EARTH SAT RESEARCH (S-E) RADIONAVIGATION FIXED SAT Satellite (Active) SATELLITE (S-E) SATELLITE FIXED SATELLITE (S-E) FIXED SATELLITE

AND TIME SIGNAL SATELLITE (S-E) SATELLITE SATELLITE (E-S) SATELLITE 3 GHz ISM – 5.8 ± .075 GHz ISM – 24.125 ± 0.125 GHz 30 GHz ACTIVITY CODE 30.0 31.0 31.3 31.8 32.0 33.0 33.4 36.0 37.0 38.6 39.5 40.0 40.5 42.5 43.5 45.5 47.0 47.2 50.2 50.4 51.4 54.25 58.2 59.0 64.0 65.0 66.0 71.0 72.77 72.91 74.0 75.5 76.0 81.0 84.0 86.0 92.0 95.0 100.0 102.0 105.0 116.0 126.0 134.0 142.0 144.0 149.0 150.0 151.0 164.0 168.0 170.0 174.5 176.5 182.0 185.0 190.0 200.0 202.0 217.0 231.0 235.0 238.0 241.0 248.0 250.0 252.0 265.0 275.0 300.0

EARTH EARTH Radio- EARTH TION Radio- RADIO- RADIO- EXPLORATION FIXED EXPLORATION INTER- EARTH EXPLORATION INTER- RADIO- Mobile EARTH location location FIXED TION SAT. FIXED EARTH GOVERNMENT EXCLUSIVE MOBILE TION

NAVIGATION . (Passive) SATELLITE EARTH . (Passive) GOVERNMENT/ NON-GOVERNMENT SHARED RADIO Radio NAVIGATION Radio-

(E-S) SATELLITE SATELLITE

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location ASTRONOMY

SATELLITE location EARTH

SATELLITE (Passive) Mobile MOBILE FIXED EXPLORATION EXPLORATION FIXED EXPLORATION SATELLITE EARTH EXPL. EARTH SAT Astronomy SAT MOBILE (Passive) SATELLITE MOBILE SPACE RES. SPACE MOBILE

MOBILE ASTRONOMY EXPLORATION BROAD- MOBILE SATELLITE SATELLITE (S-E) (Passive) CASTING (E-S) MOBILE MOBILE SATELLITE SATELLITE (E-S) Satellite FIXED EARTH SATELLITE FIXED SATELLITE SATELLITE EARTH (S-E) FIXED EARTH SATELLITE INTER- EARTH (E-S) MOBILE EXPLORA

INTER- SATELLITE

SATELLITE (E-S) SATELLITE SATELLITE INTER- . MOBILE MOBILE MOBILE EXPLORA Amateur (Passive) SATELLITE SATELLITE SATELLITE SATELLITE SATELLITE SATELLITE SATELLITE

SAT. (Passive) SAT. RADIO-

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EXPLORATION RADIO- INTER- EXPLORATION SPACE

(S-E) (E-S) Amateur Satellite SATELLITE (S-E) SATELLITE SATELLITE (S-E) SATELLITE MOBILE MOBILE NAVIGATION (Passive) SATELLITE SATELLITE (Passive)

NAVIGATION AMATEUR RESEARCH (Passive) EARTH

INTER- FIXED (Passive) SPACE RADIO- RADIO- (Passive) Radiolocation RADIO- SATELLITE EXPL. SAT RADIO- MOBILE SATELLITE Fixed LOCATION FIXED RES. SPACE SATELLITE

RESEARCH FIXED LOCATION

(S-E) NAVIGATION FI XED FIXED SATELLITE (Passive) SATELLITE FIXED

SPACE RESEARCH SPACE NAVIGATION Fixed BROAD- RADIO FIXED SPACE RADIO FIXED (Passive) EARTH EXPLORA RADIO- CASTING INTER-SATELLITE (E-S) (Passive) MOBILE SPACE RES. SPACE RESEARCH LOCATION SATELLITE AMATEUR SATELLITE AMATEUR AMATEUR SATELLITE AMATEUR AMATEUR SATELLITE AMATEUR NAVIGATION SATELLITE (E-S) SATELLITE ASTRONOMY SPACE SPACE RADIO-

SPACE (S-E) SATELLITE Amateur SPACE INTER- RADIO- SPACE (S-E) SATELLITE NON-GOVERNMENT EXCLUSIVE MOBILE RESEARCH RESEARCH NAVIGATION MOBILE MOBILE (E-S) RESEARCH RESEARCH SATELLITE NAVIGATION RESEARCH FIXED SPACE FIXED FIXED FIXED (Passive) Amateur FIXED SPACE MOBILE SPACE RADIO SPACE MOBILE MOBILE MOBILE MOBILE (Passive) SATELLITE (Passive) (Passive) MOBILE

(Passive) RESEARCH MOBILE

(Passive) (Passive) (Passive) SATELLITE (Passive) (Passive) SATELLITE(S-E)

RESEARCH MOBILE

/BROAD- RESEARCH RESEARCH MOBILE MOBILE ASTRONOMY MOBILE MOBILE SATELLITE MOBILE Amateur Satellite MOBILE CASTING/ RESEARCH SPACE SATELLITE (E-S) SATELLITE (S-E) RADIO- MOBILE SPACE MOBILE MOBILE MOBILE MOBILE MOBILE MOBILE MOBILE (E-S) MOBILE MOBILE MOBILE MOBILE SATELLITE MOBILE* * MOBILE SATELLITE

RADIONAVIGATION FIXED FIXED SATELLITE RADIONAVIGATION

NAVIGATION MOBILE MOBILE . (E-S) RESEARCH SATELLITE (S-E) SATELLITE SATELLITE SATELLITE SATELLITE FIXED FIXED MOBILE MOBILE MOBILE SATELLITE SAT

FIXED (S-E) (E-S)

EARTH FIXED BROAD- FIXED RADIO- RADIO RADIO RADIO AMATEUR AMATEUR AMATEUR FIXED EXPLORATION TION FIXED FIXED

EARTH EXPL. EARTH ASTRONOMY ASTRONOMY

CASTING FIXED ASTRONOMY MOBILE FIXED RADIO FIXED EARTH FIXED FIXED

FIXED FIXED ime Signal RADIO FIXED SATELLITE FIXED SATELLITE RADIO MOBILE LOCATION FIXED ALLOCATION USAGE DESIGNATION RADIO FIXED (E-S) RADIO- (S-E) MOBILE

FIXED MOBILE Standard RADIO- SATELLITE (Passive) SATELLITE FIXED FIXED FIXED FIXED FIXED FIXED FIXED FIXED FIXED FIXED RADIO- FIXED RADIO- SATELLITE (Passive) FIXED EARTH (E-S) Time Signal Time (E-S) EXPLORATION LOCATION RADIOLOCATION ASTRONOMY RADIONAVIGATION ASTRONOMY Satellite (S-E) LOCATION ASTRONOMY Satellite (S-E) FIXED FIXED ASTRONOMY SATELLITE FIXED SATELLITE Frequency and SATELLITE and T SATELLITE NAVIGATION NAVIGATION SATELLITE (E-S) SATELLITE AMATEUR SATELLITE AMATEUR Stand. Frequency SATELLITE (Passive) SATELLITE SPACE RES. (Passive) SPACE FIXED SAT. EXPLORA SERVICE EXAMPLE DESCRIPTION ISM – 61.25 ± .250 GHz ISM – 122.5 ± .500 GHz ISM – 245.0 ± 1GHz Primary FIXED Capital Letters 59-64 GHz IS DESIGNATED FOR 30 GHz UNLICENSED DEVICES 300 GHz Secondary Mobile 1st Capital with lower case letters Permitted /BROADCASTING/ Capital Letters between oblique strokes * EXCEPT AERO MOBILE (R) ** EXCEPT AERO MOBILE WAVELENGTH 3 x 107m 3 x 10 6m 3 x 10 5m 30,000 m 3,000 m 300 m 30 m 3 m 30 cm 3 cm 0.3 cm 0.03 cm 3 x 10 5Å 3 x 104Å 3 x 103Å 3 x 102Å10 3 x 10Å x 10 3Å 10 x 3 x 10 -1Å3 x 10 -2 Å3 10 x -3Å3 x -4 Å3 -5Å3 -6Å 3 x 10-7Å ‡‡ BAND TO BE DESIGNATED FOR MIXED USE BAND

DESIGNATIONS VERY LOW FREQUENCY (VLF) LF MF HF VHF UHF SHF EHF INFRARED VISIBLE ULTRAVIOLET X-RAY GAMMA-RAY COSMIC-RAY PLEASE NOTE: THE SPACING ALLOTED THE SERVICES IN THE

SPECTRUM SEGMENTS SHOWN IS NOT PROPORTIONAL TO THE # BAND ALLOCATED TO PERSONAL COMMUNICATIONS SERVICES (PCS)

C Radar

PLS X

ACTIVITIES Audible Range AM Broadcast FM Broadcast RadarBands Sub-Millimeter Visible Ultraviolet Gamma-ray Cosmic-ray ACTUAL AMOUNT OF SPECTRUM OCCUPIED.

Infra-sonics Sonics Ultra-sonics Microwaves Infrared X-ray ENT OF C TM OM AR M EP E D R . C .S E 13 14 15 16 17 18 19 20 21 22 23 24 25

N U U.S. DEPARTMENT OF COMMERCE FREQUENCY 0 10 Hz 100 Hz 1 kHz 10 kHz 100 kHz 1 MHz 10 MHz 100 MHz 1 GHz 10 GHz 100 GHz 1 THz 10 Hz 10 Hz 10 Hz 10 Hz 10 Hz 10 Hz 10 Hz 10 Hz 10 Hz 10 Hz 10 Hz 10 Hz 10 Hz

N A

I I

O T A

N National Telecommunications and Information Administration R A

L S

T N E I THE RADIO SPECTRUM L Office of Spectrum Management E M C D O A 3 kHz 300 GHz M N MAGNIFIED ABOVE M O TI U A NI CA RM March 1996 TIONS & INFO CHEAT SHEET

Wireless Spectrum for Dummies TO LEARN MORE, GO TO The electromagnetic spectrum has www.ecompany.com business opportunities. The U.S. government and the Federal AND TYPE IN been around for as long as the universe, Communications Commission have responded by reallocating Spectrum but from all the attention heaped on it huge swaths of spectrum for new uses and auctioning slices to the recently, you’d think it had just surfaced yesterday. New digital highest bidders for prices expected to reach well into the billions. and wireless technologies—from cell phones to satellites The future of many giant communications companies to high-definition television—are dramatically changing rests on the outcome of those auctions. It’s tricky busi- 30 how we use the airwaves and presenting enormous new MHz ness and complex science. Here’s a primer. 60 Major Commercial Wireless Services* The radio spectrum starts at 3 KHz 90 Broadcast TV AM/FM Radio 535 to 1,605 KHz Channels 2-4 (VHF) 54 to 72 MHz 120 Channels 5-6 (VHF) 76 to 88 MHz 88 to 108 MHz Channels 7-13 (VHF) 174 to 216 MHz 150 Channels 14-20 (UHF) 470 to 512 MHz Digital TV Channels 21-36 (UHF) 512 to 608 MHz 180 54 to 88 MHz Channels 38-69 (UHF) 614 to 806 MHz 174 to 216 MHz See also 3G Broadband Wireless below 210 470 to 806 MHz Broadcasters have started transmitting digital signals, but rollout is slow due to sluggish sales of digital TV sets and 3G Broadband Wireless 240 reluctance by cable operators to carry HDTV. By 2006, all 746 to 764 MHz; 776 to 794 MHz broadcasters are expected to switch over to digital TV, To be used for “third-generation” advanced wireless services. 270 although that deadline may not hold. Broadcasters’ analog Now houses TV channels 60-69 but is scheduled for auction spectrum will be reauctioned for new wireless services. in March 2001. 3G services may not launch for years, 300 though, because broadcasters don’t have to leave the band MHz until 2006 at the earliest. Cellular Phone Service 600 806 to 902 MHz Waning in popularity as PCS takes off. 3G Broadband Wireless (proposed) 900 1,710 to 1,855 MHz 2,500 to 2,690 MHz 1,200 Personal Communications Service (PCS) The Clinton administration has proposed auctioning this 1,850 to 1,990 MHz spectrum for 3G broadband wireless services. This band is used for digital cellular phone service. 1,500 Considered a 2G (second-generation) cellular service. Dominated by big carriers such as AT&T, Cingular Wireless Wireless Communications Service (WCS) 1,800 (a joint venture of SBC and BellSouth), and Sprint. 2,305 to 2,320 MHz; 2,345 to 2,360 MHz Intended for wireless data services; proximity to the satellite 2,100 radio band could make it a good addition to digital radio Satellite-Delivered Digital Radio services in the future. 2,400 2,320 to 2,325 MHz Sirius Satellite Radio and XM Satellite Radio paid a combined $173.2 million for licenses in 1997. They plan Direct Broadcast Satellite (DBS) 2,700 to launch services in spring 2001. 12.2 to 12.7 GHz EchoStar and DirecTV now dominate this fast-growing business, 3 offering hundreds of TV channels via satellite. They have become GHz Multichannel Multipoint Distribution Service (MMDS) major competitors to cable TV companies. Both DBS firms are 6 2,150 to 2,680 MHz adding interactivity using wire-line and satellite back channels. Sprint and WorldCom bought several of the failing “wireless cable” companies with MMDS spectrum and are converting 9 them from TV service to two-way digital data services. Digital Electronic Message Service (DEMS) 24.25 to 24.45 GHz; 25.05 to 25.25 GHz 12 This high-capacity allocation carries a lot of data but the signal Teledesic can’t travel far. Teligent owns most of the licenses and offers 15 18.8 to 19.3 GHz broadband data services to businesses in dense, urban areas. 28.6 to 29.1 GHz 18 Teledesic, the two-way digital satellite service scheduled for full deployment by 2005, plans to use the 18-GHz Local Multipoint Distribution Service (LMDS) band for downstream transmissions and the 28-GHz 27.5 to 29.5 GHz; 31.0 to 31.3 GHz 21 band for upstream. Teledesic’s investors include wireless XO Communications (the merger of NextLink and Concentric), pioneer Craig McCaw, Bill Gates, and Saudi prince Al- a venture founded by Craig McCaw, dominates this band, with 24 Waleed bin Talal. 95 percent coverage in the top 30 markets. Winstar also holds some licenses here. Both are building fixed wireless systems. 27 39 GHz Fixed Wireless Service 38.6 GHz to 40 GHz *This diagram shows only a select number of U.S. commercial services. 30 Winstar was the top bidder at the May auction of this Not represented are hundreds of more minor commercial and GHz noncommercial services. The government is the single largest user of spectrum, paying $161 million for 931 licenses. It plans to U.S. airwaves. It runs services ranging from law enforcement radio to offer fixed wireless services in combination with its LMDS

WORLD PERSPECTIVES/TONY STONE IMAGES: EXPLANATION GRAPHIC BY NIGEL HOLMES GRAPHIC BY EXPLANATION IMAGES: STONE PERSPECTIVES/TONY WORLD satellite space research and top-secret military communications. capacity at 28 GHz. The radio spectrum ends at 300 GHz

DECEMBER 2000 www.ecompany.com Electromagnetic Spectrum - Introduction Page 1 of 5

Electromagnetic Spectrum Measuring the electromagnetic spectrum

You actually know more about it than you may think! The electromagnetic (EM) spectrum is just a name that scientists give a bunch of types of radiation when they want to talk about them as a group. Radiation is energy that travels and spreads out as it goes-- visible light that comes from a lamp in your house or radio waves that come from a radio station are two types of electromagnetic radiation. Other examples of EM radiation are microwaves, infrared and ultraviolet light, X-rays and gamma-rays. Hotter, more energetic objects and events create higher energy radiation than cool objects. Only extremely hot objects or particles moving at very high velocities can create high-energy radiation like X- rays and gamma-rays.

Here are the different types of radiation in the EM spectrum, in order from lowest energy to highest:

Radio: yes, this is the same kind of energy that radio stations emit into the air for your boom box to capture and turn into your favorite Mozart, Madonna, or Coolio tunes. But radio waves are also emitted by other things ... such as stars and gases in space. You may not be able to dance to what these objects emit, but you can use it to learn what they are made of.

Microwaves: they will cook your popcorn in just a few minutes! In space, microwaves are used by astronomers to learn about the structure of nearby galaxies, including our own Milky Way!

Infrared: we often think of this as being the same thing as 'heat', because it makes our skin feel warm. In space, IR light maps the dust between stars.

Visible: yes, this is the part that our eyes see. Visible radiation is emitted by everything from fireflies to light bulbs to stars ... also by fast-moving particles hitting other particles.

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Ultraviolet: we know that the Sun is a source of ultraviolet (or UV) radiation, because it is the UV rays that cause our skin to burn! Stars and other "hot" objects in space emit UV radiation.

X-rays: your doctor uses them to look at your bones and your dentist to look at your teeth. Hot gases in the Universe also emit X-rays .

Gamma-rays: radioactive materials (some natural and others made by man in things like nuclear power plants) can emit gamma-rays. Big particle accelerators that scientists use to help them understand what matter is made of can sometimes generate gamma- rays. But the biggest gamma-ray generator of all is the Universe! It makes gamma radiation in all kinds of ways.

A Radio Wave is not a Gamma-Ray, a Microwave is not an X-ray ... or is it?

We may think that radio waves are completely different physical objects or events than gamma-rays. They are produced in very different ways, and we detect them in different ways. But are they really different things? The answer is 'no'. Radio waves, visible light, X-rays, and all the other parts of the electromagnetic spectrum are fundamentally the same thing. They are all electromagnetic radiation.

Electromagnetic radiation can be described in terms of a stream of photons, which are massless particles each traveling in a wave-like pattern and moving at the speed of light. Each photon contains a certain amount (or bundle) of energy, and all electromagnetic radiation consists of these

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photons. The only difference between the various types of electromagnetic radiation is the amount of energy found in the photons. Radio waves have photons with low energies, microwaves have a little more energy than radio waves, infrared has still more, then visible, ultraviolet, X-rays, and ... the most energetic of all ... gamma-rays.

Actually, the electromagnetic spectrum can be expressed in terms of energy, wavelength, or frequency. Each way of thinking about the EM spectrum is related to the others in a precise mathematical way. So why do we have three ways of describing things, each with a different set of physical units? After all, frequency is measured in cycles per second (which is called a Hertz), wavelength is measured in meters, and energy is measured in electron volts.

The answer is that scientists don't like to use big numbers when they don't have to. It is much easier to say or write "two kilometers or 2 km" than "two thousand meters or 2,000 m". So generally, scientists use whatever units are easiest for whatever they are working with. In radio astronomy, astronomers tend to use wavelengths or frequencies. This is because most of the radio part of the EM spectrum falls in the range from a about 1 cm to 1 km, and 1 kilohertz (kHz) to 1 megahertz (MHz). The radio is a very broad part of the EM spectrum. Infrared astronomers also use wavelength to describe their part of the EM spectrum. They tend to use microns (or millionths of meters) for wavelengths, so that they can say their part of the EM spectrum falls in the range 1 to 100 microns. Optical astronomers use wavelengths as well. In the older "CGS" version of the metric system, the units used were angstroms. An Angstrom is equal to 0.0000000001 meters (10-10 m in scientific notation)! In the newer "SI" version of the metric system, we think of visible light in units of nanometers or 0.000000001 meters (10-9 m). In this system, the violet, blue, green, yellow, orange, and red light we know so well has wavelengths between 400 and 700 nanometers. This range is only a small part of the entire EM spectrum, so you can tell that the light we see is just a little fraction of all the EM radiation around us! By the time you get to the ultraviolet, X-ray, and gamma-ray regions of the EM spectrum, lengths have become too tiny to think about any more. So scientists usually refer to these photons by their energies, which are measured in electron volts. Ultraviolet radiation falls in the range from a few electron volts (eV) to a about 100 eV. X-ray photons have energies in the range 100 eV to 100,000 eV (or 100 keV). Gamma-rays then are all the photons with energies greater than 100 keV.

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Show me a chart of the wavelength, frequency, and energy regimes of the spectrum ! Why Do We Have to Go to Space to See All of the Electromagnetic Spectrum?

Electromagnetic radiation from space is unable to reach the surface of the Earth except at a very few wavelengths, such as the visible spectrum and radio frequencies. Astronomers can get above enough of the Earth's atmosphere to observe at some infrared wavelengths from mountain tops or by flying their telescopes in an aircraft. Experiments can also be taken up to altitudes as high as 35 km by balloons which can operate for months. Rocket flights can take instruments all the way above the Earth's atmosphere for just a few minutes before they fall back to Earth, but a great many important first results in astronomy and astrophysics came from just those few minutes of observations. For long-term observations, however, it is best to have your detector on an orbiting satellite ... and get above it all!

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Imagine the Universe is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Nicholas White (Director), within the Laboratory for High Energy Astrophysics at NASA's Goddard Space Flight Center.

The Imagine Team Project Leader: Dr. Jim Lochner

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The Electromagnetic Spectrum

Show me a movie about the Electromagnetic Spectrum!

QuickTime format AVI format

More about the Electromagnetic Spectrum

As it was explained in the Electromagnetic Spectrum - Level 1 of Imagine the Universe!, electromagnetic radiation can be described in terms of a stream of photons, each traveling in a wave-like pattern, moving at the speed of light and carrying some amount of energy. It was pointed out that the only difference between radio waves, visible light, and gamma-rays is the energy of the photons. Radio waves have photons with low energies, microwaves have a little more energy than radio waves, infrared has still more, then visible, ultraviolet, X-rays, and gamma-rays.

Actually, the amount of energy a photon has makes it sometimes behave more like a wave and sometimes more like a particle. This is called the " wave-particle duality" of light. It is important to understand that we are not talking about a difference in what light IS, but only in how it behaves. Low energy photons (such as radio) behave more like waves, while higher energy photons (such as X-rays) behave more like particles. This is an important difference for scientists to know when they design detectors and telescopes to try to 'see' EM radiation from very low to very high energies. In fact, scientists choose whichever description of light they need for their study.

The truth is, the electromagnetic spectrum can be expressed in terms of energy, wavelength, or frequency. Each way of thinking about the EM spectrum is related to the others in a precise mathematical way. The relationships are: the wavelength equals the speed of light divided by the frequency or lambda = c / nu

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and energy equals Planck's constant times the frequency or E = h x nu

(lambda and nu are just letters from the Greek alphabet that scientists like to use rather than l or f. It just helps them to keep things straight!) Both the speed of light and Planck's constant are, well, constant: They never change their values. Ever. The speed of light is equal to 299,792,458 m/s (186,000 miles/second). Planck's constant is equal to 6.626 x 10-27 erg- seconds.

Show me a chart of the wavelength, frequency, and energy regimes of the spectrum ! Space Observatories in Different Regions of the EM Spectrum

Radio observatories

At present, there is one radio observatory in space. There are plans, however, for one more in the next year. The Very Long Baseline Interferometry (VLBI) Space Observatory Program (VSOP) is a Japanese mission that launched in February 1997. RADIOASTRON, a Russian mission, is scheduled for 1998. NASA will be supporting both missions with its Deep Space Network radio telescope facilities around the world.

Radio waves CAN make it through the Earth's atmosphere without significant obstacles (In fact radio telescopes can observe even on cloudy days!). However, the availability of a space radio observatory complements radio telescopes on the Earth in some important ways.

One is a special technique used in radio astronomy called "interferometry". Radio astronomers can combine data from two telescopes that are very far apart and create images which have the same resolution as if they had a single telescope as big as the distance between the two telescopes! That means radio telescope arrays can see incredibly small details. One such array is called the Very Large Baseline Array

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(VLBA): it consists of ten radio telescopes which reach all the way from Hawaii to Puerto Rico: nearly a third of the way around the world! By putting a radio telescope in orbit around the Earth, radio astronomers could make images as if they had a radio telescope the size of the entire planet!

Microwave observatories

The Microwave Anisotropy Probe (MAP), launched in the summer of 2001, will measure the temperature fluctuations of the cosmic microwave background radiation over the entire sky in order to address such fundamental questions as:

z What are the values of the cosmological parameters of the Big Bang theory? z How did structures of galaxies form in the Universe? z When did the first structure of galaxies form?

The previous microwave observatory, the Cosmic Background Explorer (COBE), observed the entire sky making very precise measurements of the temperature of the "microwave background".

The sky is a source of microwaves in every direction, most often called the microwave background. This background is believed to be the remnant from the "Big Bang" scientists believe our Universe began with. It is believed that a very long time ago all of space was scrunched together in a very small, hot ball. The ball exploded outward and became our Universe as it expanded and cooled. Over the course of the past several billion years (the Universe's actual age is still a matter of debate, but is believed to be somewhere between ten and twenty billion years), it has cooled all the way to just three degrees above zero. It is this "three degrees" that we measure as the microwave background.

COBE mapped out the entire microwave background, carefully measuring very small differences in temperatures from one direction to another. Astronomers have many theories about the beginning of the Universe and their theories predict how the microwave background would look. The very precise measurements made by COBE eliminated a great many of the theories about the Big Bang.

Infrared observatories

The biggest infrared observatory currently in orbit is the brand new Infrared Space Observatory (ISO), launched in November 1995 by the European Space Agency. ISO will operate for at least two years barring unforeseen circumstances. It has been placed in an elliptical orbit with a 24 hour period which keeps it in view of the ground stations at all times, a

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necessary arrangement since ISO transmits observations as it makes them rather than storing information for later playback. ISO will able to observe from 2.5 to 240 microns.

Early in the next decade, NASA will be launching the Space Infrared Telescope Facility (SIRTF). SIRTF will use an passive cooling system (i.e. it radiates away its own heat rather than requiring an active refrigerator system like most other space infrared observatories) and it will be launched well away from the Earth where it will not have to contend with Earth occultation of sources nor with the comparatively warm environment in near-Earth space.

Another major infrared facility coming soon will be the Stratospheric Observatory for Infrared Astronomy (SOFIA). Although SOFIA will not be an orbiting facility, it will carry a large telescope within a 747 aircraft flying at an altitude sufficient to get it well above most of the Earth's infrared absorbing atmosphere. SOFIA will be replacing the Kuiper Airborne Observatory.

Visible spectrum observatories

The only visual observatory in orbit at the moment is the Hubble Space Telescope (HST). Like radio observatories in space, there are visible observatories already on the ground. However, Hubble has several special advantages over them.

HST's biggest advantage is, because it is above the Earth's atmosphere, it does not suffer distorted vision from the air. If the air was all the same temperature above a telescope and there was no wind (or the wind was perfectly constant), telescopes would have a perfect view through the air. Alas, this is not how our atmosphere works. There are small temperature differences, wind speed changes, pressure differences, and so on. This causes light passing through air to suffer tiny wobbles. It gets bent a little, much like light gets bent by a pair of glasses. But unlike glasses, two light beams coming from the same direction do not get bent in quite the same way. You've probably seen this before -- looking along the top of the road on a hot day, everything seems to shimmer over the black road surface. This blurs the image telescopes see, limiting their ability to resolve objects. On a good night in an observatory on a high mountain, the amount of distortion caused by the atmosphere can be very small. But the Space Telescope has NO distortion from the atmosphere and its perfect view gives it many many times better resolution than even the best ground- based telescopes on the best nights.

Another advantage of the Space Telescope is that without the atmosphere in the way, it can see more than just the visible spectrum. The Space Telescope can also see ultraviolet light which normally is absorbed by the Earth's atmosphere and cannot be seen by regular telescopes. So the Space

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Telescope can see a much wider portion of the spectrum.

Ultraviolet observatories

Right now there are no dedicated ultraviolet observatories in orbit. The Hubble Space Telescope can perform a great deal of observing at ultraviolet wavelengths, but it has a very fairly small field of view. Until September 1996, the International Ultraviolet Explorer (IUE) was operating and observing ultraviolet radiation. Its demise, although unfortunate, was hardly premature: IUE was launched in January, 1978 with planned operations of three years. IUE functioned more or less like a regular ground based observatory save that the telescope operator and scientist did not actually visit the telescope, but sent it commands from the ground. Other than some care in the selection of materials for filters, a UV telescope like IUE is very much like a regular visible light telescope.

In addition to IUE, there have been fairly important recent UV space missions. A reusable shuttle package called Astro has been flown twice in the cargo bay of the space shuttle: it consisted of a set of three UV telescopes. Unlike HST, the Astro UV telescopes had very large fields of view and so could take images of larger objects in the sky -- like galaxies. For instance, if the Hubble Space Telescope and the Astro telescopes were used to look at the Comet Hale-Bopp, Hubble would be able to take spectacular pictures of the core of the comet. The Astro telescopes would be able to take pictures of the entire comet, core and tail.

Extreme Ultraviolet observatories

There are two extreme ultraviolet observatories in space at the moment. One of them is the very first extreme ultraviolet observatory ever, the Extreme Ultraviolet Explorer (EUVE). Astronomers have been somewhat reluctant to explore from space at the extreme ultraviolet wavelengths since all theory strongly suggests that the interstellar medium (the tiny traces of gases and dust between the stars) would absorb radiation in this portion of the spectrum. However, when the Extreme Ultraviolet Explorer (EUVE) was launched, observations showed that the solar system is located within a bubble in the local interstellar medium. The region around the Sun is relativity devoid of gas and dust which allows the EUVE instruments to see much further than theory predicted.

Another extreme ultraviolet observatory currently operating is the Array of Low Energy X-ray Imaging Sensors (ALEXIS). Although its name indicates that it is an X-ray observatory, the range of energy ALEXIS is exploring is at the very lowest end of the X-ray spectrum and often considered to be extreme ultraviolet. ALEXIS was launched on 25 Apr 1993 on a Pegasus rocket. During launch, a hinge plate supporting one of

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the solar panels broke. However, the satellite survived, and the panel remains connected to the satellite via the electrical cables and a tether, and it still provides the requisit power to the satellite. ALEXIS is spinning about an axis pointed approximately toward the sun. ALEXIS provides sky maps on a daily basis whenever the satellite is not in a 100% sunlight orbit. These sky maps are used to study diffuse x-ray emission, monitor the brightness of known EUV objects, and to detect transient objects.

X-ray observatories

There are several X-ray observatories currently operating in space with more to be launched in the next few years.

The Rossi X-ray Timing Explorer (RXTE) was launched on December 30, 1995. RXTE is able to make very precise timing measurements of X-ray objects, particularly those which show patterns in their X-ray emissions over very short time periods, such as certain neutron star systems and pulsars.

Other X-ray observatories currently operating in space include ROSAT, a joint venture between the United States, Germany, and the United Kingdom; the Advanced Satellite for Cosmology and Astrophysics (ASCA), a joint U.S.-Japan venture; the Kvant astrophysics module attached to the Russian space station Mir, and Beppo SAX, an Italian X- ray satellite.

NASA launched another major new X-ray astronomy satellite, the Chandra X-ray Observatory (CXO), in mid 1999.

Gamma-ray observatories

The Compton Gamma-Ray Observatory (CGRO) was launched by the space shuttle in April 1991. The observatory's instruments are dedicated to observing the gamma-ray sky, including locating gamma-ray burst sources, monitoring solar flares, and other highly energetic astrophysical phenomenon. An unexpected discovery which Compton has made was the observation of gamma-ray burst events coming from the Earth itself at the top of thunderstorm systems. The cause of this phenomenon is not known, but it is currently suspected to be related to "Sprites": lightening flashes which are occasionally seen jumping upwards from cloud tops to the upper stratosphere.

The Russian gamma-ray observatory Granat has exhausted its control fuel. Its last maneuver was to initiate a roll which has allowed it to perform a continuous all-sky survey.

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The next major gamma-ray missions in the near future include SWIFT and the Gamma-Ray Large Area Space Telescope (GLAST). SWIFT will study gamma-ray bursts, and be capable of quickly pointing narrow field X-ray and optical detectors in the direction of gamma-ray bursts detected by its large field detectors. GLAST will have a field of view twice as large as that of the Compton Gamma-Ray Observatory, and a sensitivity of up to 50 times greater than Compton's EGRET instrument. GLAST will study a wide range of gamma-ray objects, including pulsars, black holes, active galaxies, diffuse gamma-ray emission, and gamma ray bursts. Also slated for launch is the future U.S.-Russia mission Spectrum X-Gamma will make pointed observations in both X-ray and gamma-ray wavelength regimes.

URL of this page: http://imagine.gsfc.nasa.gov/docs/science/know_l2/emspectrum.html

The Imagine Team Project Leader: Dr. Jim Lochner

NASA's privacy statement

Do you have a question, problem or comment about this web site? Please let us know.

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Consumer Information Bureau FCC > CIB Home > Consumer Info Directory - History of Wire and Broadcast site map

May 1993

HISTORY OF WIRE

AND

BROADCAST COMMUNICATION

EARLY COMMUNICATIONS

At the turn of the century, radio was confined to wireless telegraph, largely for marine radio purposes, and code communication for comparatively short distances. Today radio has many hearing and visual communication uses on land, at sea, and in the air.

WIRE TELEGRAPH

The invention of the steamboat and locomotive greatly increased the speed of communication. However, it was the telegraph that strengthened the ties of our national life and unity.

Samuel F. B. Morse, while a professor of arts and design at New York University in 1835, proved that signals could be transmitted by wire. He used pulses of current to deflect an electromagnet, which moved a marker to produce written codes on a strip of paper -the invention of Morse Code. The following year, the device was modified to emboss the paper with dots and dashes. He gave a public demonstration in 1838, but it was not until five years later that Congress -- reflecting public apathy -- funded $30,000 to construct an experimental telegraph line from Washington to Baltimore, a distance of 40 miles.

Six years later, members of Congress witnessed the sending and receiving of messages over part of the telegraph line. Before the line had reached Baltimore, the Whig party held its national convention there, and on May 1, 1844, nominated Henry Clay. This news was hand-carried to Annapolis Junction (between Washington and Baltimore) where Morse's partner, Alfred Vail, wired it to the Capitol. This was the first news dispatched by electric telegraph.

The message, "What hath God wrought?" sent later by "Morse Code" from the old Supreme Court chamber in the United States Capitol to his partner in Baltimore, officially opened the completed line of May 24, 1844.

Three days later the Democratic National Convention was held in Baltimore. Van Buren seemed the likely choice, but his opponent, James K. Polk, won the nomination. This news was telegraphed to Washington, but skeptics refused to believe it. Only after persons arrived by train from Baltimore to confirm the reports were many convinced of the telegraph's value.

Samuel Morse and his associates obtained private funds to extend their line to

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Philadelphia and New York. Small telegraph companies, meanwhile began functioning in the East, South, and Midwest. Dispatching trains by telegraph started in 1851, the same year Western Union began business. Western Union built its first transcontinental telegraph line in 1861, mainly along railroad rights-of-way.

In 1881, the Postal Telegraph System entered the field for economic reasons, and merged with Western Union in 1943. Today only Western Union offers a nationwide telegraph service. Some independent telegraph companies exist, but they are small and mostly serve railroads or particular industries in limited areas of the United States.

The original Morse telegraph printed code on tape. However, in the United States the operation developed into sending by key and receiving by ear. A trained Morse operator could transmit 40 to 50 words per minute. Automatic transmission, introduced in 1914, handled more than twice that number.

In 1913 Western Union developed multiplexing, which it made possible to transmit eight messages simultaneously over a single wire (four in each direction). Teleprinter machines came into use about 1925. Varioplex, introduced in 1936, enabled a single wire to carry 72 transmissions at the same time (36 in each direction). Two years later Western Union introduced the first of its automatic facsimile devices. In 1959 Western Union inaugurated TELEX, which enables subscribers to the teleprinter service to dial each other directly.

OCEAN CABLE TELEGRAPH

With capital obtained from private subscriptions in New York and London and, in part, appropriated by the British and United States governments, an attempt was made in 1857 to lay a cable under the Atlantic Ocean. The cable broke after 355 miles has been laid by a ship operating from Ireland. The following June, another attempt failed. A cable was thought to be successfully laid the next month but it became inoperative. Another cable-laying effort, in 1865, proved futile after the many attempts made.

On July 27, 1866, the steamship "Great Eastern" completed laying a new cable from Ireland to Newfoundland. Returning to mid-Atlantic, the ship located and raised the cable used in a previous attempt, spliced it, and extended it to Newfoundland, where it was landed on September 8, 1866. Thus, America and Europe were linked by two cables and other ocean cables followed.

Ocean cables were operated by repeating the messages along the route. In 1921, "regenerators" were developed for direct transmission between terminals. Less than 300 single letters a minute could be sent over the original transatlantic cable. Later new "permalloy" cables raised that capacity to about 2,400 letters a minute.

Until 1877, all rapid long-distance communication depended upon the telegraph. That year, a rival technology developed that would again change the face of communication -- the telephone. By 1879, patent litigation between Western Union and the infant telephone system was ended in an agreement that largely separated the two services.

EARLY WIRE TELEGRAPH

Electrical telegraph still could transmit only a few words per minute, or required Morse-code, which is one-way communication.

On June 2, 1875, Alexander Graham Bell while experimenting with a technique called http://www.fcc.gov/cib/evol.html 12/21/2001 Consumer Facts - History of Wire and Broadcast Page 3 of 14

"harmonic telegraph" discovered he could hear sound over a wire. The sound was that of a twanging clock spring. On March 10, 1876, Bell transmitted the first complete sentence heard over a wire. He said: "Mr. Watson, come here, I want you." It was received by his associate, Thomas A. Watson, in an adjoining room of their tiny Boston laboratory.

United States Patent No. 174,465, issued to Bell in 1876, became recognized as the "most valuable patent." Yet early efforts to popularize the telephone were met with disappointment. Though people paid to hear Bell lecture on "the miracle discovery of the age," for a long time they seemed unaware of its possibilities.

However, in 1877, construction of the first regular telephone line from Boston to Somerville, Massachusetts were completed. By the end of 1880, there were 47,900 telephones in the United States. The following year telephone service between Boston and Providence had been established. Service between New York and Chicago started in 1892, and between New York and Boston in 1894. Transcontinental service by overhead wire was not inaugurated until 1915. The first switchboard was set up in Boston in 1877. The first regular telephone exchange was established in New Haven in 1878. Early telephones were leased in pairs to subscribers. The subscriber was required to put up his own line to connect with another.

In 1889, the rotary telephone dial was invented by Almon B. Strowger, a Kansas City undertaker. The first dial exchange was installed at La Porte, Indiana, in 1892. In 1943, Philadelphia was the last major area to give up dual service.

The first Bell telephone company started in 1878. This is now known as the American Telephone and Telegraph Company (AT&T), which was incorporated in 1885.

Toward the close of the 19th century, huge numbers of overhead wires were being used in major cities. The wires caused problems because of snow, sleet and other bad weather conditions. With these problems it was necessary to develop sturdier overhead cables. In 1888, 100 wires could be combined into a large cable. By 1985 fiber cables had replaced wires. Today a pair of fiber cables can carry up to 25,000 phone conversations simultaneously.

Experiments with underground telephone cable began in 1882, but it was not until 1902 that the first long distance buried cable was placed in operation between New York and Newark, New Jersey. The first cross-continent underground cable line was opened in 1942.

Submarine telephone cables have long connected this country with Cuba. The first transatlantic telephone cable connecting Newfoundland with England was opened in 1956. Later that year a submarine telephone cable from the State of Washington to Alaska was put into operation. Hawaii was linked by telephone cable with the mainland in 1957, and a telephone cable to France began operating in 1959. Several telephone cables now link North America and Europe together.

The first coaxial cable experiment opened between New York and Philadelphia in 1936. One pair of coaxial units simultaneously carried 1,860 telephone conversations or 600 conversations and two TV programs. Each of these 1,860 voice pathways were equipped to provide up to 18 telegraph circuits. Commercial service was inaugurated between Stevens Point, Wisconsin, and Minneapolis, Minnesota, in 1941. Coast-to- coast service was inaugurated in 1951 when the Japanese Peace Conference in San Francisco, California, was televised.

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RADIO TELEGRAPH

Few radio broadcasts travel through the air exclusively, while many are sent over telephone wires. In the 1860s James Clerk Maxwell, a Scottish physicist, predicted the existence of radio waves, and in 1886 Heinrich Rudolph Hertz, a German physicist, demonstrated that rapid variations of electric current could be projected into space in the form of radio waves similar to those of light and heat.

But it remained for Guglielmo Marconi, an Italian inventor, to prove the feasibility of radio communication. He sent and received his first radio signal in Italy in 1895. By 1899 he flashed the first wireless signal across the English Channel and two years later received the letter "S", telegraphed from England to Newfoundland. This was the first successful transatlantic radiotelegraph message in 1902.

Wireless signals proved effective in communication for rescue work when a sea disaster occurred. Effective communication was able to exist between ships and ship to shore points. A number of ocean liners installed wireless equipment. In 1899 the United States Army established wireless communications with a lightship off Fire Island, New York. Two years later the Navy adopted a wireless system. Up to then, the Navy had been using visual signaling and homing pigeons for communication.

In 1901, radiotelegraph service was instituted between five Hawaiian Islands. By 1903, a Marconi station located in Wellfleet, Massachusetts, carried an exchange or greetings between President Theodore Roosevelt and King Edward VII. In 1905 the naval battle of Port Arthur in the Russo-Japanese war was reported by wireless, and in 1906 the U.S. Weather Bureau experimented with radiotelegraphy to speed notice of weather conditions.

In 1909, Robert E. Peary, arctic explorer, radiotelegraphed: "I found the Pole". In 1910 Marconi opened regular American-European radiotelegraph service, which several months later, enabled an escaped British murderer to be apprehended on the high seas. In 1912, the first transpacific radiotelegraph service linked San Francisco with Hawaii.

Overseas radiotelegraph service developed slowly, primarily because the initial radiotelegraph set discharged electricity within the circuit and between the electrodes was unstable causing a high amount of interference. The Alexanderson high-frequency alternator and the De Forest tube resolved many of these early technical problems. The Navy made major use of radio transmitters -- especially Alexanderson alternators, the only reliable long-distance wireless transmitters - for the duration.

During World War I, governments began using radiotelegraph to be alert of events and to instruct the movement of troops and supplies. World War II demonstrated the value of radio and spurred its development and later utilization for peacetime purposes. Radiotelegraph circuits to other countries enabled persons almost anywhere in the United States to communicate with practically any place on earth.

Since 1923, pictures have been transmitted by wire, when a photograph was sent from Washington to Baltimore in a test. The first transatlantic radiophoto relay came in 1924 when the Radio Corporation of America beamed a picture of Charles Evans Hughes from London to New York. RCA inaugurated regular radiophoto service in 1926.

Two radio communication companies once had domestic networks connecting certain http://www.fcc.gov/cib/evol.html 12/21/2001 Consumer Facts - History of Wire and Broadcast Page 5 of 14

large cities, but these were closed in World War II. However, microwave and other developments have made it possible for domestic telegraph communication to be carried largely in part over radio circuits. In 1945 Western Union established the first microwave beam system, connecting New York and Philadelphia. This has since been extended and is being developed into a coast-to-coast system. By 1988 Western Union could transmit about 2,000 telegrams simultaneously in each direction.

RADIO

The first time the human voice was transmitted by radio is debateable. Claims to that distinction range from the phase, "Hello Rainey" spoken by Natan B. Stubblefield to a test partner near Murray, Kentucky, in 1892, to an experimental program of talk and music by Reginald A. Fessenden, of Brant Rock, Massachusetts, in 1906, which was heard by radio-equipped ships within several hundred miles.

In 1915 speech was first transmitted across the continent from New York City to San Francisco and across the Atlantic Ocean from Naval radio station NAA at Arlington, Virginia, to the Eiffel Tower in Paris. There was some experimental military radiotelephony in World War I between ground and aircraft.

The first ship-to-shore two way radio conversation occurred in 1922, between Deal Beach, New Jersey, and the S.S. America, 400 miles at sea. However, it was not until 1929 that high seas public radiotelephone service was inaugurated. At that time telephone contact could be made only with ships within 1,500 miles of shore. Today there is the ability to telephone nearly every large ship wherever it may be on the globe.

Commercial radiotelephony linking North America with Europe was opened in 1927, and with South America three years later. In 1935 the first telephone call was made around the world, using a combination of wire and radio circuits.

Until 1936, all American transatlantic telephone communication had to be routed through England. In that year, a direct radiotelephone circuit was opened to Paris. Telephone connection by radio and cable is now accessible with 187 foreign points.

Microwave telephone transmission was first sent across the English Channel in 1930. A microwave telephone system, between Boston and New York, became operative in 1947. The first overseas telephone call from a moving automobile was made from St. Louis to Honolulu in 1946.

EARLY WIRE REGULATION

Federal regulation of interstate electrical communication may be said to date from passage of the Post Roads Act in 1866. The Postmaster General became authorized to fix rates annually for Government telegrams.

In 1887, Congress gave the Interstate Commerce Commission (ICC) authority to require telegraph companies to interconnect their lines for more extended public service.

Government regulation of the accounting practices of wire communication carriers began with the Mann Elkins Act of 1910. This authorized the ICC to establish uniform systems of accounts for telegraph and telephone carriers, to make valuation studies of certain wire telegraph companies, and to be informed of extensions and improvements in order to keep these valuation studies current. Telephone and telegraph carriers http://www.fcc.gov/cib/evol.html 12/21/2001 Consumer Facts - History of Wire and Broadcast Page 6 of 14

were required to file monthly and annual financial reports with the ICC.

EARLY RADIO REGULATION

The Mann-Elkins Act also gave the ICC certain regulatory powers over radiotelegraph carriers. This statute, extended provisions of the Interstate Commerce Act of 1887 to cover wireless telegraph.

Meanwhile, the usefulness of radiotelegraph in protecting life and property at sea became of such importance that a preliminary international wireless conference was held in Berlin in 1903 to consider a common distress call for ships and to provide for wireless communication between ship and shore as well as between ships.

The first radio distress call from an American vessel (a Navy relief ship) occurred in 1905. Jack Binns, a radio operator, made world news in 1909 when he remained at his post on the stricken steamship Republic to summon aid with the British radio distress call "C Q D" (calling all stations, disaster). Later that same year the S.S. Arapahoe brought help with "SOS" (save our ship) which was adopted as an international radiotelegraph distress call in 1906 and is still in use. "Mayday" was adopted in 1927 as the international distress call for radiotelephony, which is still used today.

WIRELESS SHIP ACT OF 1910

The first legislation dealing with marine radio was approved by Congress in 1910. Known as the Wireless Ship Act, it required installation of wireless apparatus and operators on sea-going passenger vessels with 50 or more passengers travelling between ports 200 or miles apart, had to carry apparatus capable of reaching 100 miles day or night, and have an operator to run it.

RADIO ACT OF 1912

To further wireless uniformity, regulations were adopted by the Berlin International Radiotelegraphic Convention in London of 1912. To comply with its obligations under that treaty, the United States Congress enacted the Radio Act of 1912. This was the first domestic law for general control of radio communication. Later that year, Congress amended the Wireless Ship Act of 1910 to cover large cargo vessels, to require an auxiliary source of power supply on ships, an adequate means of communications between the radio room and bridge, and two or more skilled radio operators on certain passenger vessels.

The Radio Act regulated the character of emissions, transmission of distress calls, set aside certain frequencies for government use, and placed licensing of wireless stations and operators under the Secretary of Commerce and Labor, now responsible for the licensing of radio stations and operators. The actual licensing process began in 1912. This law governed the regulation of radio, including the as yet little-known concept of broadcasting until 1927.

WORLD WAR I PERIOD

From August 1, 1918, to July 31, 1919, the Federal Government exercised control over telephone and telegraph communications as a war measure. In 1920, Congress authorized the Secretary of the Navy to use government operated radio stations for the transmission of press and private commercial messages between ships and between ship and shore. Rates were reviewed by the Interstate Commerce Commission (ICC) to be sure they were reasonable. http://www.fcc.gov/cib/evol.html 12/21/2001 Consumer Facts - History of Wire and Broadcast Page 7 of 14

The Transportation Act of 1920 directed the ICC to prescribe the depreciation rates and charges of telephone and telegraph companies. Also in 1920, the Interstate Commerce Act was amended to permit consolidation of telephone companies when approved by the ICC.

An Executive Order, issued in 1921 pursuant to the Cable Landing License Act, authorized the Department of State to receive all applications to land or operate ocean cables, and to consult the President to the granting or revoking of such licenses. Presidents between 1869 and 1921 had exercised this control under their broad executive powers.

EARLY RADIO BROADCASTING

The Radio Act of 1912 did not anticipate nor provide for broadcasting. However, this did not present any serious problems prior to World War I. Since most early broadcasting was experimental.

In 1919 broadcasting stations were classified as "limited commercial stations". In 1922 the "wavelength" of 360 meters (approximately 830 kilocycles of kilohertz) was assigned for the transmission of "important news items, entertainment, lectures, sermons, and similar matter". Stations engaged in this service held limited commercial authorizations from the Department of Commerce.

Recommendations of the First National Radio Conference, held in Washington, D.C., in 1922, resulted in further regulation from the Secretary of Commerce. A new type of broadcast station came into existence, with a minimum power of 500 watts and maximum power not to exceed 1,000 watts, with two frequencies (750 and 833 kilocycles or kilohertz) assigned for program transmissions.

This service was introduced as the Amplitude Modulation (AM) Broadcast service. The rapid development of AM broadcast stations triggered subsequent National Radio Conferences (1923 and 1924). The Department of Commerce allocated the present standard broadcast band (AM being the only form of broadcast at that time), and authorized power up to 5000 watts for experimental use.

The increase in the number of AM radio broadcast stations caused a large amount of interference that in 1925, a Fourth National Radio Conference asked for a limitation to be placed on AM broadcast time and power.

In the early 1920s there were more than 200, though almost all had left the air by the end of decade. The Secretary of Commerce was unable to deal with the situation because court decisions held that the Radio Act of 1912 did not give the Secretary sufficient authority. Many broadcasters changed their frequencies and increased their power and operating time at will. This caused serious transmission and reception problems.

RADIO ACT OF 1927 AND THE FEDERAL RADIO COMMISSION

In 1926 President Coolidge urged Congress to remedy the chaos in AM broadcasting. The result was the Dill-White Radio Act of 1927, which was signed on February 23, 1927. The Act created a five-member Federal Radio Commission with regulatory powers over radio, including the issuance of station licenses, the allocation for frequency bands to various services, assignment of specified frequencies to individual stations, and control of station power. http://www.fcc.gov/cib/evol.html 12/21/2001 Consumer Facts - History of Wire and Broadcast Page 8 of 14

The Act delegated authority to the Secretary of Commerce to inspect radio stations, to examine and license radio operators, and to assign radio call signs. The Federal Radio Commission was to keep radio service relatively equal throughout the country.

The Federal Radio Commission began functioning on March 15, 1927. Much of its early activity was devoted to resolving problems in the AM broadcast band. Accommodating the 732 AM stations already in operation became impossible. As a result, new rules and regulations forced approximately 150 of the operators to surrender their licenses.

COMMUNICATIONS ACT OF 1934

The Radio Act of 1927 did not give the Federal Radio Commission jurisdiction over telegraph and telephone carriers. The Post Office Department, the Interstate Commerce Commission and the Department of State exercised certain authority with respect to telegraph service.

Some aspects of regulation of telephone service was under the jurisdiction of the ICC, with the FRC having authority over broadcasting. This divided and often overlapping authority caused a great deal of confusion.

President Franklin D. Roosevelt in 1933, requested the Secretary of Commerce to appoint an interdepartmental committee for studying electronic communications. The Committee reported that "the communications service, as far as congressional action is involved, should be regulated by a single body." A recommendation was made for the establishment of a new agency that would regulate all interstate and foreign communication by wire and radio, telegraphy, telephone and broadcast.

On February 26, 1934, the President sent a special message to Congress urging the creation of the Federal Communications Commission (FCC). The following day Senator Dill and Representative Sam Rayburn of Texas introduced bills to carry out this recommendation. The Senate Bill (S.3285) passed the House on June 1, 1934, and the conference report was adopted by both houses eight days later. The Communications Act was signed by President Roosevelt on June 1934. Particular parts of it became effective July 1, 1934; other parts on July 11, 1934. And thus the FCC was born.

The law authorized the FCC broadcast regulatory functions previously exercised by the FRC. At that point, regulation of telegraph and telephone operations became the responsibility of the ICC. Jurisdiction over telegraph rates was under Post Office Department, with jurisdiction of the Cable Landing License Act a responsibility of the Department of State. The Communications Act allowed the FCC additional authority, including regulation of rates of interstate and international common carriers, and domestic administration of international agreements relating generally to electronic communication.

The stated purposes of the Act are "regulating interstate and foreign commerce in communication by wire and radio so as to make available, so far as possible, to all the people of the United States a rapid, efficient, nationwide, and worldwide wire and radio communication service with adequate facilities at reasonable charges... the national defense... promoting safety of life and property through the use of wire and radio communication..."

The Act applies "to all interstate and foreign communication by wire or radio and all interstate and foreign transmission of energy by radio, which originates and/or is received within the United States, and to all persons engaged within the United States http://www.fcc.gov/cib/evol.html 12/21/2001 Consumer Facts - History of Wire and Broadcast Page 9 of 14

in such communication or such transmission of energy by radio, and to the licensing and regulation of all radio stations..."

The Communications Act of 1934, as amended, consists of six major sections or "titles":

Title I - Explains the purposes and applications of the Act, the terms and duties of the Commissioners, and confers general powers.

Title II - Covers communications common carriers that are subject to Commission regulation.

Title III - Relates to radio and is divided into four parts: radio licensing and regulation, radio equipment, radio operators on board ship, radio installations on vessels carrying passengers for hire, assistance for public telecommunications facilities;

Title IV - Clarifies procedural and administrative provisions.

Title V - Prescribes penalties and forfeitures for violators.

Title VI - Prohibits unauthorized interception and publication of communications by wire or radio and gives the President certain powers to deal with communication matters in the event of war or other national emergency and provision of telephone service for the disabled.

The FCC began operating on July 11, 1934. Seven Commissioners were appointed by the President, and confirmed by the Senate. The President designated one of the Commissioners as Chairman of the FCC. Most appointed to the FCC were lawyers with public utility experience or government service. Not more than four of the seven Commissioners could be members of the same political party. In July, 1983, the Act was amended to reduce the composition of the Commission to five, not more than three members of the same political party.

The first Commission members were Eugene O. Sykes, Thad H. Brown, Paul A. Walker, Norman Case, Irvin Stewart, George Henry Paine, and Hampson Gary. The Commissioners duties are to supervise all FCC activities, delegate responsibilities to staff units, bureaus, and to committees of Commissioners.

The first project of the FCC was to change substandard program and advertising policies in broadcasting. The FCC was to decide if a station's policies and programs were in the public interest.

The authority of the FCC extends to Guam, Puerto Rico, Virgin Islands, American Samoa and the Marianas Islands, but not the Canal Zone. The FCC does not regulate federal government radio operators, but is responsible for the domestic administration of wire and radio provisions of treaties and other international agreements to which the United States is a party.

To carry out the regulatory responsibilities of the Commission, Commissioners are assisted by a General Counsel, a Managing Director, a Director of Public Affairs, a Director of Legislation, a Chief of Plans and Policy, Administrative Law Judges, Review Board and the chiefs of five operating bureaus, who are delegated various licensing and grant authority. The five operating bureaus are:

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Mass Media Bureau - Responsible for licensing all radio, television, cable systems and administering the enforcement program relative to all Mass Media Services.

Common Carrier Bureau - Responsible for telephone, satellite operations, cellular and other mobile services.

Private Radio Bureau - Responsible for licensing two-way radio services used in police cars, taxicabs, aircraft, ships, etc.

Field Operations Bureau - Responsible for detecting radio violations and enforcing the FCC Rules and Regulations.

Office of Engineering and Technology Bureau - Responsible for spectrum management and technical standards, researching new technologies affecting communications. Authorize equipment compliance with technical standards before it is to be released to the public for purchase.

COMMON CARRIER REGULATION

The Commission regulates interstate and foreign communication by telephone and telegraph, whether by wire, radio, or satellite. Purely intrastate communication is not subject to FCC jurisdiction but comes under the authority of state utility commissions. To resolve matters of concern to the FCC and state public utility commissions a "Federal-State Joint Board" is formed, consisting of regulators from federal and state commissions.

The FCC regulates rates for interstate telephone and telegraph service, as well as for services between the United States, foreign and overseas points, and ships at sea.

The Commission has jurisdiction of records and accounts to be kept by common carriers. Under this authority, it has established uniform systems of accounts for carriers to act upon. Commission regulation in this respect includes the establishment and maintenance of original cost accounting, continuing property records, pension cost records, and depreciation records.

There are over 1300 privately owned telephone companies providing local telephone service in the United States. These companies include 22 Bell Operating Companies (BOCs) that formerly were part of the integrated Bell System. AT&T had been providing almost completely all the long distance telephone service to the United States. As part of the court-approved 1984 AT&T "divestiture" decree, carriers are now part of the seven regional holding companies led to the termination of the research, manufacturing, and long-distance and local telephone service facilities owned by A&T. This left the aging local systems to the seven spun-off Bell operating companies being: Ameritech, Bell Atlantic, Bell South, NYNEX, Pacific Telesis, Southwestern Bell, and U.S. West. These seven companies provide service to about 85 percent of consumers telecommunications needs. The remaining population is serviced by local exchange carriers that are either small independent telephone companies or large independent telephone companies, such as GTE, Continental, United and Central.

There are also a large number of firms that provide long distance service in the United States. The number of companies seeking to purchase the "trunk side" or premium connections now available under equal access increased from 13 in 1982 to 276 in http://www.fcc.gov/cib/evol.html 12/21/2001 Consumer Facts - History of Wire and Broadcast Page 11 of 14

1987 to 692 in 1992.

Extensive revisions of the FCC Act, occurring particularly in 1952 and during the period 1960 to 1962, made important changes in the FCC's organization and procedures. The Communications Satellite Act of 1962 gave the FCC new responsibilities with respect to space communication. A Presidential Executive Order of 1963 augmented its duties to ready the communication services under its jurisdiction to deal with possible national emergency situations.

In the past decade, there have been two major developments concerning telecommunications policy in the United States:

(1) "break-up" or divestiture of AT&T, and (2) FCC directed liberalization of the United States telecommunications industry. The divestiture resulted from a court decided consent decree that settled an antitrust complaint brought by the Department of Justice alleging that AT&T had monopolized, or attempted to monopolize, a number of markets for telecommunications equipment and services.

Under the terms of the decree, the Bell Operating Companies are not allowed to provide long distance service outside certain specified geographic areas called Local Access Transport Areas (LATA). Also the Bell Operating Companies are prohibited from providing information services, and from manufacturing equipment, and they are subject to certain general line of business restrictions that limit the service and products they may provide.

The divestiture of AT&T should not be confused with the ongoing measures taken by the FCC to promote liberalization of the United States telecommunications industry. The process began in the customer premises equipment (CPE) market in the late 1950s. Traditionally, telephone company tariffs prohibited the interconnection of customer-supplied terminal equipment.

In an effort to enhance the Long Distance Service marketplace, the FCC gradually has replaced unwieldy regulation with a streamlined approach that establishes a firm basis for competition and maximizes beneficial uses of the existing telecommunications network. For example, Commission policies that promote open entry and prohibit restrictions on resale and shared use of telecommunications services have helped to move rates closer to costs. These policies have fostered innovation through the introduction of new technology and new services.

SATELLITE COMMUNICATION

The Communications Satellite Act of 1962 provides for U.S. participation in a global commercial communications satellite system by a private corporation, the Communications Satellite Corporation, under Government regulation. The principal task of that corporation is to plan, establish and operate the system in cooperation with other nations to furnish, for hire, satellite relay of international and interstate telephone and telegraph services, including television.

The U.S. portion of the system is subject to the same regulatory controls by the FCC as are other communications common carriers. The Commission must ensure effective competition in the procurement of equipment and approve all financing by the corporation, except the initial stock issue. The FCC also must approve the technical characteristics of the satellite system and authorize terminal stations in the U.S.

BROADCAST REGULATION http://www.fcc.gov/cib/evol.html 12/21/2001 Consumer Facts - History of Wire and Broadcast Page 12 of 14

The Communications Act deems broadcasting not to be a common carrier operation and prohibits the Commission from censoring programs or interfering with the right of freedom of speech on the air. Consequently, FCC regulation of broadcasting concerns two general phases:

z 1. Allocation of portions of the spectrum to the different types of broadcast services in accordance with the Commission's rules and regulations to carry out the intent of international agreements, the Communications Act and other domestic laws affecting broadcasting.

z 2. Consideration of individual stations, applications to build and operate; assignment of frequencies, power, operating time, and call letters; periodic inspection of equipment and the engineering aspects of operation; renewal of licenses and transfers and assignments of facilities; modifications and changes in existing facilities; and licensing operators of these, as well as all other nongovernment transmitters.

Broadcast stations are licensed to serve the "public convenience, interest, and necessity." The Communications Act requires applicants to be legally, technically, and financially qualified, and to show that their proposed operation will be in the public interest. Each broadcast station licensee, must meet these requirements, and assure that its programming serves the public interest, and in particular, meets the needs of the community it serves. The Commission periodically reviews the overall performance of stations, usually when they apply for license renewal, to see if they have lived up to their obligations and the promises made in applying for facilities.

The Communications Act also considers a prearranged broadcast contest determining the result of intellectual knowledge, intellectual skill, or chance with intent of deception to be a violation.

The Commission has revised the national and local radio ownership rules so that a single licensee can own up to 18 AM stations and 18 FM stations nationwide and 12 TV stations. The previous limit was 12 of each service.

On the local level, markets with 15 or more stations, a single licensee will be allowed to own up to 2 AM and 2 FM stations, provided that the proposed combination does not lead to excessive concentration in the market. Excessive concentration will be presumed where the combined audience share of the stations to be jointly owned exceeds 25 percent. For markets with fewer than 15 stations, a single licensee is permitted to own up to 3 stations, no more than 2 of which may be in the same service, if the combination constitutes less than 50 percent of the stations in the market.

The Communications Act requires the Commission to study new uses for communication technology and encourage its development. The Act also stresses the use of radio to protect life and property. The Commission has authorized many uses for radio other than for broadcasting and common carrier services. Collectively these new radio services, combined with older radio services, make up a group known as the Private Radio Bureau. These services embrace practically all radio operations that are neither broadcast nor open for hire to the general public.

The Private Radio Bureau covers use of radio by ships afloat and planes in the air; by rail and motor carriers; by agencies concerned with police and fire protection, and national defense and other emergency services; by industry, manufacturers, public http://www.fcc.gov/cib/evol.html 12/21/2001 Consumer Facts - History of Wire and Broadcast Page 13 of 14

utilities and other business; and by individuals for private convenience or for amateur communication. In the 1980's amateurs made major contributions to computer- generated message systems, and packet radio. These new systems, as well as the formerly used ones, were used to quickly and accurately distribute communications during and after disasters such as storms, earthquakes, and forest fires.

CABLE TELEVISION

Cable TV was developed initially in the late 1940s in communities unable to receive clear TV reception because of terrain or distance from TV stations. Cable system operators placed their antennas in areas having stable reception, picked up broadcast station signals, and then distributed it by coaxial cable to subscribers for a fee.

In 1950, there were only 70 cable TV operations in the United States, serving 14,000 cable television homes/subscribers. By 1992 cable television serviced 64 percent of U.S. homes. The number of 24-hour calbe radio networks has more than doubled since 1984.

Cable has the capability of offering clearer pictures than home antennae, particularly for color TV, and can offer large numbers of channels for TV signals and various other services. Some systems being currently constructed in large metropolitan areas are planning to offer 100 to 500 channels. Many systems feature separate channels for weather, stock market reports, wire service news, and FM radio. Some cable operators originate their own programs and provide access channels and leased channels for public and institutional uses. Most systems now offer 12 to 35 channels, with 20 the average.

Cable systems are concentrated in all cities/communities (except some rural areas). In large metropolitan areas, cable subscribership is increasing due to poor conventional television reception caused by "canyons" created by tall buildings or skyscrapers. By 1992 the largest system located in Woodbury, New York, has more than 376,000 subscribers.

The Commission asserted limited jurisdiction over cable TV in 1962. It first established rules in 1965 for systems that received signals by microwave. (Microwave stations have always been licensed by the FCC.) In 1966, the Commission established rules for all cable systems, regardless to whether they were served by microwave or not. A comprehensive revision of the rules was adopted February 2, 1972, and became effective March 31, 1972. The rules adopted in 1972 required cable television operators to have a certificate of compliance from the FCC before operating a cable television system or adding a television broadcast signal. By 1980, the FCC dropped most of the remaining cable television rules.

In October 1984, the U.S. Congress adopted a comprehensive national cable bill known as the Cable Communications Policy Act of 1984 (Cable Act). The Act, which amends the Communications Act of 1934, establishes policies in the areas of ownership, channel usage franchise provisions and renewals, subscriber rates and privacy, obscenity and lockboxes, unauthorized reception of services, equal employment opportunity, and pole attachments. The new law also delineates jurisdictional boundaries among federal, state, and local authorities with respect to the regulation of cable television systems. The Commission modified its rules to implement the Cable Act in April 1985.

The cable industry became involved with news in the 1980's. Many expectations revolved the start-up of Ted Turner's Cable News Network (CNN), which began

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operation in June 1980.

NEW SERVICES

During the middle of 1981 HDTV (High-Definition Television) was first demonstrated in the United States. By 1988, the FCC decided that any future broadcast HDTV system must be compatible with existing receivers and will have to use no more than present broadcast spectrum. In March 1990 the FCC voted to select only high definition television (HDTV) standards that would fit into the present six MHz channels allocated for television.

MMDS (Multichannel Multipoint Distribution Service) was originally created by the FCC in the 1960s. The channels were expanded to carry video signals in the 1970s. By 1988, MMDS served only a small proportion of the national audience and faced a bleak future as the number of cities without cable service dwindled.

In recent years, the FCC has taken a marketplace approach to regulation in an effort to promote competition, to increase the number of new services, to streamline and to eliminate cumbersome rules and regulations; thereby, promoting increased usage of the telecommunications industry.

last reviewed/updated on 9/25/01 FCC Home | Search | Updates | E-Filing | Initiatives | For Consumers | Find People Federal Communications Phone: 888-CALL-FCC (225-5322) - Web Policies & Privacy Statement Commission TTY: 888-TELL-FCC (835-5322) - Customer Service Standards 445 12th Street SW Fax: 202-418-0232 - Freedom of Information Act Washington, DC 20554 E-mail: [email protected] More FCC Contact Information...

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Station Identification and Call Signs

WHY STATIONS MUST BE IDENTIFIED

With millions of radio stations furnishing a variety of communication services throughout the world, it is necessary that their transmissions carry distinctive call signs. These call signs have a three-fold purpose. They identify the nationality of the station, the type of station, and the individual station. Radio call signs, in effect, are the "license plates" that identify communication traffic on the radio highways.

The need for station identification is emphasized by the fact that the United States, which leads all other countries in the use of radio, now has some 85 different kinds of radio services providing land, sea, air and space communication services.

HOW CALL SIGNS ARE DESIGNATED

Since the early days of wireless telegraphy, starting with marine use, radio stations have had their own identification. Under international agreement, since 1927 the alphabet has been divided among nations for basic call sign use. The United States, for example, is assigned three letters--N,K, and W-- to serve as initial call letters for the exclusive use of its radio stations. It also shares the initial letter A with some other countries. The letter A is assigned to the Army and Air Force; N to the Navy and Coast Guard, and K and W to domestic stations, both government and nongovernment.

The Communications Act gives the FCC authority to designate call letters to all United States radio stations. This is done on an individual station basis. A and N block assignments are designated for government use. Further details on the FCC's requirements for the identification of radio stations may be found in the Code of Federal Regulations, Title 47, Part 2, (Subpart D) of the rules. Some types of radio stations and equipment, such as radar stations and diathermy equipment, are exempt from such requirements.

BROADCAST STATION IDENTIFICATION

Broadcast stations in this country are assigned call signs beginning with K or W. Generally speaking, those beginning with K are assigned to stations West of the Mississippi River and in U.S. territories and possessions, while those beginning with W are assigned to broadcast stations East of the Mississippi River. During radio's infancy, most of the broadcast stations were in the East. As stations began operating, the Mississippi became the dividing line between K and W call signs. The few exceptions to existing call signs within this system were assigned before the allocation plan was adopted. Station KDKA, Pittsburgh, Pennsylvania, is one example.

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Since the beginning of broadcasting, stations have had the privilege of requesting specific call signs. In requesting their preferences for certain letters of the alphabet, broadcasters have presented combinations of names, places or slogans. For example, the letters NBC are used for stations owned by the National Broadcasting Company, CBS for those of the Columbia Broadcasting System, and ABC for the American Broadcasting Companies. Examples of individual station call letters are: WGN, Chicago ("World's Greatest Newspaper"), WNYC, New York (New York City municipal station); KAGH, Crossett, AK, ("Keep Arkansas Green Home"); WIOD, Miami ("Wonderful Isle of Dreams"); WLS, Chicago ("Worlds Largest Store"); WACO, Waco Texas); WTOP, Washington, D.C. ("Top of the Dial"); KFDR, Grand Coulee, Washington, (Franklin D. Roosevelt); WCFL, Chicago ("Chicago Federation of Labor"); WMTC Vancleve, KY, ("Win Men to Christ"); WGCD, Chester, S.C. ("Wonderful Guernsey Center of Dixie"); Educational TV station WXXW, Chicago, uses the Roman numerals for its channel 20; and KABL, Oakland, CA, selected its letters to represent San Francisco's famous cable cars. If a new broadcast station makes no specific request, it is assigned a call sign by the FCC. Since 1946 the FCC has not guaranteed specific call signs to be granted prior to the grant of a construction permit or special temporary authority.

As broadcast stations began to increase in the early 1920's, the three letter call sign could no longer accommodate the growing number of stations, making it necessary to add a fourth letter.

With the advent of FM and TV in 1941, new call signs for all such stations were not assigned. Rather, since many FM and TV stations were operated by the same AM licensee at the same license area, the general practice was for the associated FM or TV station to simply add "-FM" or "-TV", to the call sign of the co-owned AM station. International Radio Regulations do not require the use of call signs by broadcast stations if some other suitable means of identification is employed. For example, many foreign stations identify by announcing, "The Voice of ... "or "Radio..."

AMATEUR CALL SIGNS

Amateur radio station call signs are assigned by an automatic system that selects the call sign from an alphabetical listing depending upon the operator's license class and mailing address. Although amateur call signs are for the purpose of identifying the station rather than the operator, call signs are often personal in nature. For example, these call signs often appear on correspondence and on automobile license plates, i.e. NJ9AZ. There are even grave stones bearing the cherished call signs of amateurs who have sent their final sign-off signal "SK".

DISTRESS CALLS

Records indicate that a British vessel used radio as early as 1899 to summon aid. The first radio distress call from an American vessel has been traced to 1905. But radio operator Jack Binns made headlines in 1909 when he stuck to his post on the stricken steamship REPUBLIC to send the distress signal then in use, "CQD". In 1912 the ill fated TITANIC flashed the same call.

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Before the turn of the century there was no special radiotelegraph call for emergencies at sea. One pioneer operator simply sent the letters "HELP" in code. In 1903, Italy suggested "SSSDDD" as an international radio emergency call. By 1904, a number of ships engaged in Atlantic trade were equipped with "wireless", as radio was then known, and they recruited land telegraph operators for sea duty. These operators resorted to the landline general call "CQ", meaning "attention all stations". In 1904, the Marconi Company added the letter "D" to signal distress.

Meanwhile, German ships had been using "SOE" and in 1906 Germany recommended these letters as an international distress call. This combination was deemed unsatisfactory to radiotelegraphy because the final dot was often obliterated by static or other interference. The American delegation to an international conference suggested "NC", which is the call for help in flag signaling. However, international agreement was reached on "SOS", which became effective in 1906, though "CDQ" continued to be used by British ships for some years thereafter.

For radiotelephone purposes, or voice transmission, the international distress call is "MAYDAY", which corresponds to the French phrase "m'aider" meaning "help me". It was adopted from a British proposal approved by an international convention in 1927. It has since been used by military as well as civilian ships and aircraft. In 1963, an international telecommunication conference agreed that the distress signals "SOS" and "MAYDAY" should also be used in space communication.

The Communications Act specifically bans transmission of false or deceptive signals.

last reviewed/updated on 7/24/01 FCC Home | Search | Updates | E-Filing | Initiatives | For Consumers | Find People Federal Communications Phone: 888-CALL-FCC (225-5322) - Web Policies & Privacy Statement Commission TTY: 888-TELL-FCC (835-5322) - Customer Service Standards 445 12th Street SW Fax: 202-418-0232 - Freedom of Information Act Washington, DC 20554 E-mail: [email protected] More FCC Contact Information...

http://www.fcc.gov/cib/statid.html 12/21/2001