Choose the BEST answer. 14.

SINAD is calculated as:

a. signal voltage divided by noise voltage
1. Electromagnetic waves travel through a vacuum at b. signal power divided by noise power
A. speeds that are proportional to their frequency c. first add the signal power to the noise power, then
B. speed that are inversely proportional to their divide by noise power
frequency d. none of the above
C. the same speed
D. any of the above 15. Signal-to-Noise ratio is calculated as:
a. signal power divided by noise power
2. Which has the same power spectral density? b. signal voltage divided by noise voltage
A. Brown Noise c. first add the signal power to the noise power, then
B. White noise divide by noise power
C. White and Brown noise d. none of the above
D. None of the above
16. When two noise voltages, V1 and V2, are combined,
the total voltage VT is:
3. Flicker noise is called A. VT = (V1 + V2)/2
A. pink noise B. VT = sqrt(V1 x V1 + V2 x V2)
B. white noise C. VT = sqrt(V1 x V2)
C. brown noise D. VT = V1 + V2
D. none of the above
17. “Pink” noise has:
4. Which occurs due to equilibrium fluctuations A. constant power
A. thermal noise B. equal power per Hertz
B. Johnson noise C. equal power per octave
C. Thermal and Johnson noise D. none of the above
D. None of the above
18. So called “1/f” noise is also called:
5. Shot noise A. random noise
A. Poisson process B. white noise
B. Stochastic process C. pink noise
C. Stochastic & poisson process D. partition noise
D. None of the above
19. The power density of “flicker” noise is:
6. Shot noise is A. the same at all frequencies
A. avoidable when current is 1 B. greater at low frequencies
B. avoidable when current is 0 C. greater at high frequencies
C. avoidable when current is high D. the same as “white” noise
D. none of the above
20. Shot noise is generated in:
7. Thermal noise is A. resistors
A. Power signal B. copper wire
B. Energy signal C. transistors and diodes
C. Energy and power signal D. none of the above
D. None of the above
21. Thermal noise is generated in:
8. Noise A. transistors and diodes
A. has infinite power B. resistors
B. has infinite energy C. copper wire
C. infinite energy and power D. all of the above
D. none of the above
22. “Man-made” noise can come from:
9. The Capacity of the channel can be increased by A. static
A. increasing the signal power B. equipment that sparks
B. increasing channel bandwidth C. temperature
C. increasing channel bandwidth and signal power D. all of the above
D. none of the above
23. Noise in a communication system originates in:
10. How long doses it take light to travel 1.0m? A. the sender
A. 3.3 micro-s B. the channel
B. 3.3 ns C. the receiver
C. 3.3 ms D. all of the above
D. 3.3 s
24. The baseband bandwidth for a voice-grade (telephone)
11. Which of the following correctly lists electromagnetic signal is:
waves in order from longest to shortest wavelength A. 20 Hz to 15,000 Hz
A. radio waves, infrared, gamma rays, ultraviolet B. at least 5 kHz
B. television, infrared, visible light, x-rays C. approximately 3 kHz
C. gamma rays, ultraviolet, infrared, microwaves D. none of the above
D. microwaves, ultraviolet, visible light, gamma rays
25. The collection of sinusoidal frequencies present in a
12. Part, or parts, of a sinusoidal carrier that can be modulated carrier is called its:
modulated are: A. frequency-domain representation
a. its amplitude B. Fourier series
b. its amplitude and frequency C. Spectrum
c. its amplitude, frequency, and phase angle D. all of the above
d. its amplitude, frequency, and direction
26. Distortion is caused by:
13. Noise Figure is a measure of: A. creation of harmonics of baseband frequencies
a. how much noise is in the channel B. baseband frequencies “mixing” with each other
b. how much noise an amplifier adds to a signal C. shift in phase relationships between baseband
c. how much noise is in a communications system frequencies
d. signal-to-noise ratio in dB D. all of the above
27. The wavelength of a radio signal is: A. Cosmic C. Atmospheric
A. equal to f ÷ c B. Solar D. Galactic
B. equal to c ÷ λ
C. how far the signal can travel without distortion 41. Which of the following is not a simplex communication
D. the distance a wave travels in one period system?
A. TV broadcasting C. radar
28. FDM stands for: paging services D. facsimile
A. Fast Digital Modulation
B. Frequency-Division Multiplexing 42. As assigned by the Federal Communications
C. Frequency Domain Measurement Commission, cellular radio systems operate in the
D. none of the above A. LF and HF bands C. VHF and UHF bands
E. HF and VHF band D. UHF and microwave
29. TDM stands for: bands
A. Time-Division Multiplexing
B. Two-level Digital Modulation 43. The spectral density of white noise
C. Time Domain Measurement
D. none of the above A. varies with bandwidth
B. varies with amplitude
30. When two or more signals share a common channel, it C. varies with frequency
is called: D. is constant
A. multiplexing
B. sub-channeling 44. Theoretical power of white noise
C. signal switching A. is infinite
D. SINAD B. is finite
C. is zero
31. The bandwidth required for a modulated carrier D. depends on the frequency of the signal
depends on:
A. the carrier frequency 45. An amplifier has an output SNR of 16 dB and noise
B. the baseband frequency range figure of 5.4 dB. Its input SNR is
C. the signal-to-noise ratio A. 21.4 dB
D. the signal-plus-noise to noise ratio B. 10.4 dB
C. 16 dB
32. Radians per second is equal to: D. 5.4 dB
A. f x 2π
B. 2π x f 46. AN amplifier has an output signal power of 10W and an
C. the phase angle output noise power of 0.01 W. The signal-to-power
D. none of the above power ratio is
A. 60 dB
33. A complete communication system must include: B. 30 dB
A. a transmitter and receiver C. 20 dB
B. a multiplexer, a demultiplexer, and a channel D. 10 dB
C. a transmitter, a receiver, and a channel
D. a transmitter, a receiver, and a spectrum analyzer 47. The available thermal noise power per unit bandwidth
will ___ if the value of resistance is doubles while
maintaining the ambient temperature constant
A. remain unchanged
34. The transmission of radio waves was first done by: B. be doubled
A. Marconi C. be halved
B. Hertz D. be increased four-fold
C. Bell
D. Maxwell 48. In a particular system, the signal power is 10 dBm, and
noise power is -1dBm, The SNR will be
35. The person who sent the first radio signal across the A. -11 dB
Atlantic ocean was: B. -10dB
A. Bell C. 9 dB
B. Maxwell D. 11 dB
C. Marconi
D. Hertz 49. AN amplifier has a noise figure of 1.6. Its equivalent
noise temperature is
36. The theory of radio waves was originated by: A. 754 K
A. Bell B. 290 K
B. Maxwell C. 174 K
C. Marconi D. 0 K
D. Hertz
50. Equivalent noise temperatures of low-noise amplifiers
37. A system has an input resistance of 20 kΩ which are often
causes a noise voltage of 15µV. If two input A. about 1000 K
resistances, each of 20 kΩ are used in parallel, B. more than 100 K
compute the total noise voltage. C. about 0 K
A. 15 µV C. 7.5 µV D. less than 100 K
B. 30 µV D. 10.6 µV

38. Which of the following analog modulation scheme

requires the least transmitted power and least channel
bandwidth?
A. VSB C. DSB-SC
B. SSB D. AM

39. How much of the transmitted power is in the carrier in

amplitude modulation?
A. one-half C. one-third
B. three-quarters D. two-thirds

40. Which of the following noise sources is different from

others?