CHAPTER 1: INTRO TO COMMUNICATIONS SYSTEM

In a communications system, noise is most likely to affect the signal a. at the transmitter b. in the channel c. in the information source d. at the destination

b

Indicate the false statement. Fourier analysis shows that a sawtooth wave consists of a. fundamental and subharmonic sine waves b. a fundamental sine wave and an infinite number of harmonics c. fundamental and harmonic sine waves whose amplitude decreases with the harmonic number d. sinusoidal voltages, some of which are small enough to ignore in practice

a

Indicate the false statement. Modulation is used to a. reduce the bandwidth used b. separate differing transmissions c. ensure that intelligence may be transmitted over long distances d. allow the use of practicable antennas

a

Indicate the false statement. From the transmitter the signal deterioration because of noise is usually a. unwanted energy b. predictable in character c. present in the transmitter d. due to any cause

b

Indicate the true statement. Most receivers conform to the a. amplitude-modulated group b. frequency-modulated group c. superheterodyne group d. tuned radio frequency receiver group

c

Indicate the false statement. The need for modulation can best be exemplified by the following a. Antenna lengths will be approximately λ/4 long b. An antenna in the standard broadcast AM band is 16,000 ft c. All sound is concentrated from 20 Hz to 20 kHz d. A message is composed of unpredictable variations in both amplitude and frequency

a

Indicate the true statement. The process of sending and receiving started as early as a. the middle 1930s b. 1850 c. the beginning of the twentieth century d. the 1840s

d

Which of the steps is not included in the process of reception? a. decoding b. encoding c. storage d. interpretation

b

The acoustic channel is used for which of the following? a. UHF communications b. single-sideband communication c. television communications d. person-to-person voice communications

d

Amplitude modulation is the process of a. superimposing a low frequency on a high frequency b. superimposing a high frequency on a low frequency c. carrier interruption d. frequency shift and phase shift

a