EST

1. The theory of radio waves was iriginated by?

A) Marconi
B) Bell
C) Hertz
D) None of these
E) Maxwell

2. The bandwidth required for a modulated carrier depends on:

A) the baseband frequency range
B) the signal-plus-noise to noise ratio
C) None of these
D) the carrier frequency
E) the signal-to-noise ratio

3. When two or more signals share a common channel, it is called:

A) multiplexing
B) signal switching
C) None of these
D) SINAD
E) sub-channeling

4. Distortion is caused by:

A) baseband frequencies "mixing" with each other
B) None of these
C) creation of harmonics of baseband frequencies
D) All of the above
E) baseband frequencies "mixing" with each other

5. The baseband bandwidth for a voice-grade (telephone) signal is:

A) None of these
B) at least 5 kHz
C) All of the above
D) 20 Hz to 15,000 Hz
E) approximately 3 kHz

6. The power density of "flicker" noise is:

A) the same at all frequencies
B) greater at high frequencies
C) None of these
D) greater at low frequencies
E) the same as "white" noise

7. When two noise voltages, V1 and V2, are combined, the total voltage VT is:

A) None of these
B) VT = sqrt(V1 × V1 + V2 × V2)
C) VT = sqrt(V1 × V2)
D) VT = sqrt(V1 × V2)
E) VT = (V1 + V2)/2

8. Signal-to-Noise ratio is calculated as:

A) None of these
B) signal voltage divided by noise voltage
C) signal power divided by noise power
D) first add the signal power to the noise power, then divide by noise power
E) All of the above

9. Noise Figure is a measure of:

A) None of these
B) how much noise is in a communications system
C) how much noise an amplifier adds to a signal
D) signal-to-noise ratio in dB
E) how much noise is in the channel

10. SINAD is calculated as:

A) first add the signal power to the noise power, then divide by noise power
B) None of these
C) signal power divided by noise power
D) signal voltage divided by noise voltage
E) All of the above

11. The UHF band starts at ____________________ MHz.

A) 500
B) 400
C) 300
D) None of these
E) 200

12. The VHF band starts at ____________________ MHz.

A) 30
B) 60
C) 50
D) None of these
E) 40

13. The equipment used to show signals in the frequency domain is the _________________________.

A) spectrum signal monitor
B) None of these
C) spectrum displayer
D) spectrum domain monitor
E) spectrum analyzer

14. Suppose there is 30 μV from one noise source that is combined with 40 μV from another noise source.Calculate the total noise voltage.

A) 50 μV
B) None of these
C) 30 μV
D) 60 μV
E) 40 μV

15. If you have 100 mV of signal and 10 mV of noise, both across the same 100-ohm load, what is the signal-to-noise ratio in dB?

A) 20 dB
B) None of these
C) 50 dB
D) 30 dB
E) 40 dB

16. A microwave receiver has a noise temperature of 145 K. Find its noise figure.

A) 2.5
B) 1.5
C) None of these
D) 0.5
E) 1

17. The "Miller Effect" can:

A) cause an amplifier to oscillate
B) reduce the bandwidth of an amplifier
C) All of the above
D) cause an amplifier to lose gain
E) None of these

18. The Miller Effect can be avoided by:

A) increasing the Q of the tuned circuit
B) using a common-base amplifier
C) None of these
D) it cannot be avoided
E) using a common-emitter amplifier

19. For a "frequency multiplier" to work, it requires:

A) None of these
B) an input signal that is an integer multiple of the desired frequency
C) a signal containing harmonics
D) a nonlinear circuit
E) a linear amplifier

20. The conditions for sinusoidal oscillation from an amplifier are called:

A) None of these
B) the Hartley criteria
C) the loop-gain criteria
D) the Barkhausen criteria
E) the Bode criteria

21. Generally, conductor lengths in RF circuits should be

A) None of these
B) slow
C) long
D) fast
E) short

22. At UHF frequencies and above, elements must be considered as ____________________ instead of as being "lumped".

A) connected
B) combined
C) None of these
D) dispersed
E) distributed

23. A ____________________ circuit is used to remove RF from the DC voltage bus.

A) uncoupling
B) decoupling
C) coupling
D) None of these
E) recoupling

24. What inductance would you use with a 47-pF capacitor to make a tuned circuit for 10 MHz?

A) 6.4 μH
B) 5.4 μH
C) None of these
D) 6.2 μH
E) 9.2 μH

25. What value of Q is required for a 10-MHz tuned circuit to have a bandwidth of 100 kHz?

A) 1000
B) 10
C) 500
D) of None these
E) 100

26. A tuned-circuit amplifier with a gain of 10 is being used to make an oscillator. What should be the value of the feedback ratio to satisfy the Barkhausen criteria?

A) 0.1
B) 0.3
C) None of these
D) 0.2
E) 0.5

27. If a varactor has a capacitance of 90 pF at zero volts, what will be the capacitance at 4 volts?

A) 53 pF
B) 40 pF
C) 28 pF
D) 30 pF
E) None of these

28. AM stands for:

A) Antenna Modulation
B) Amplitude Modulation
C) None of these
D) Angle Modulation
E) Audio Modulation

29. The "envelope" of an AM signal is due to:

A) None of these
B) the baseband signal
C) the amplitude signal
D) the carrier signal
E) All of the above

30. If an AM radio station increases its modulation index, you would expect:

A) None of these
B) the received RF signal to increase
C) All of the above
D) the audio to get louder at the receiver
E) the signal-to-noise ratio to increase

31. As compared to plain AM, SSB AM:

A) None of these
B) is more efficient
C) requires less bandwidth
D) requires a more complex demodulator circuit
E) All of the above

32. The SC in SSB SC stands for:

A) self-carrier
B) suppressed-carrier
C) None of these
D) sideband-carrier
E) single-carrier

33. The FM modulation index:

A) increases with both deviation and modulation frequency
B) increases with deviation and decreases with modulation frequency
C) is equal to twice the deviation
D) decreases with deviation and increases with modulation frequency
E) None of these

34. The bandwidth of an FM signal is considered to be limited because:

A) it is band-limited at the receiver
B) it is equal to the frequency deviation
C) None of these
D) the power in the outer sidebands is negligible
E) there can only be a finite number of sidebands

35. What is the relative amplitude of the third pair of sidebands of an FM signal with m = 6

A) 0.5
B) 0.11
C) None of these
D) 0.2
E) 0.3

36. A 200 kHz carrier is modulated by a 2.5kHz signal. The fourth pair of sidebands are spaced from the carrier by

A) 10 kHz
B) None of these
C) 11 kHz
D) 13 kHz
E) 12 kHz

37. An FM transmitter has a maximum deviation of 12 kHz and a maximum modulating frequency of 12 kHz. The bandwidth by Carson’s rule is

A) 20 kHz
B) 48 kHz
C) None of these
D) 50 kHz
E) 68 kHz

38. The maximum allowed deviation of the FM sound signal in TV is 25 kHz. If the actual deviation is 18 kHz, the percent modulation is

A) 50%
B) 72%
C) 80%
D) None of these
E) 100%

39. The frequency change of a crystal oscillator produced by a varactor diode is

A) fast
B) slow
C) None of these
D) large
E) small

40. Frequency modulation transmitters are more efficient because their power is increased by what type of amplifier

A) class C
B) None of these
C) class A
D) class D
E) class B

41. A reactance modulator looks like a capacitance of 35 pF in parallel with the oscillator-tuned circuit whose inductance is 50 μH and capacitance is 40 pF. What is the center frequency of the oscillator prior to FM?

A) 29 MHz
B) None of these
C) 152 MHz
D) 206 MHz
E) 100 MHz

42. The input to a PLL is 2 MHz. In order for the PLL to be locked, the VCO output must be

A) 4 MHz
B) 16 MHz
C) None of these
D) 2 MHz
E) 8 MHz

43. A class B amplifier conducts for how many degrees of an input sine wave?

A) 75 degrees
B) 180 degrees
C) 360 degrees
D) 90 degrees
E) None of these

44. An FM transmitter has a 9 MHz crystal carrier oscillator and frequency multipliers of 2, 3, 4. The output frequency is

A) None of these
B) 300 MHz
C) 220 MHz
D) 119 MHz
E) 216 MHz

45. A tuned circuit resonates at 12 MHz with an inductance of 5 μH whose resistance is 6 Ω. The circuit bandwidth is

A) 61 kHz
B) 250 kHz
C) 40 kHz
D) 191 kHz
E) None of these

46. The maximum bandwidth that an analog signal use with a sampling frequency of 108 kHz is

A) 70 kHz
B) 150 kHz
C) 54 kHz
D) None of these
E) 70 kHz

47. Transmitting data as serial binary words is called

A) T-1
B) PCM
C) CODEC
D) PAM
E) None of these

48. Sampling an analog signal produces

A) TCM
B) PAM
C) T-1
D) None of these
E) CODEC

49. Which of the following is not a common transmission line impedance?

A) 10 Ω
B) None of these
C) 120 Ω
D) 100 Ω
E) 75 Ω

50. The desirable SWR on a transmission line is

A) 2
B) None of these
C) 0
D) 5
E) 1

51. A 50Ω coax is connected to a 73Ω antenna. The SWR is

A) 1.5
B) 3.8
C) None of these
D) 1.46
E) 2.5

52. The impedance of a dipole is about

A) 73 Ω
B) None of these
C) 50 Ω
D) 50 Ω
E) 28 Ω

53. An antenna has a power gain of 15. The power applied to the antenna is 32 W. The effective radiated power is

A) 480 W
B) 483 W
C) None of these
D) 250 W
E) 372 W

54. A rectangular waveguide has a width of 1 in. and a height of 0.6 in. Its cutoff frequency is

A) 5.9 GHz
B) 1.2GHz
C) None of these
D) 10 GHz
E) 25 GHz

55. Which diode is a popular microwave oscillator

A) None of these
B) Gunn
C) Tunnel
D) Yagi
E) Radar

56. Most satellites operate in which frequency band?

A) 6 GHz to 30 GHz
B) None of these
C) 4 GHz to 30 GHz
D) 3 GHz to 30 GHz
E) 5 GHz to 30 GHz

57. The main power sources for a satellite are

A) Battery pack
B) Electricity
C) UV rays
D) None of these
E) Solar cells

58. A common up-converter and down-converter IF is

A) 60 MHz
B) 80 MHz
C) 50 MHz
D) 70 MHz
E) None of these

59. The most widely used data communications code is

A) ASCII
B) FREQUENCY
C) BINARY
D) None of these
E) DECIMAL

60. The ASCII code has

A) 8 bits
B) 7 bits
C) 9 bits
D) 10 bits
E) None of these

61. The typical bandwidth of a satellite band is

A) 750 MHz
B) 500 MHz
C) 100 MHz
D) 1000 MHz
E) None of these

62. The modulation normally used with digital data is

A) CODEC
B) None of these
C) QPSK
D) QWERTY
E) DPSK

63. The main circuit in a PSN generator is a(n)

A) XOR
B) OR
C) NOR
D) AND
E) None of these

64. Which cable length has the highest attenuation?

A) 2 KM
B) 1 KM
C) None of these
D) 5 M
E) 70 M

65. The core of a fiber-optic cable is surrounded by

A) Cladding
B) Fiber glass
C) Twisted wires
D) None of these
E) Rubber

66. The wavelength of visible light extends from

A) None of these
B) 150 to 750 nm
C) 500 to 750 nm
D) 400 to 750 nm
E) 200 to 750 nm

67. Both LEDs and ILDs operate correctly with

A) Forward bias
B) None of these
C) Side bias
D) Backward bias
E) All of the above

68. Fiber-optic with attenuations of 1.8, 3.4, 5.9 and 18 dB are linked together. The total loss is

A) 4.71 dB
B) 10 dB
C) None of these
D) 29.1 dB
E) 5.57 dB

69. The speed of light is

A) None of these
B) 300,000,000 m/s
C) 200,000,000 m/s
D) 1,000,000 m/s
E) 100,000,000 m/s

70. In ______ schemes, the voltages are on the both sides of the time axis. For example, the voltage level for 0 can be positive and the voltage level for 1 can be negative.In ______ schemes, the voltages are on the both sides of the time axis. For example, the voltage level for 0 can be positive and the voltage level for 1 can be negative.

A) polar
B) unipolar
C) All of the above
D) bipolar
E) None of these

71. ______ substitutes eight consecutive zeros with 000VB0VB.

A) None of these
B) All of the above
C) HDB3
D) B8ZS
E) B4B8

72. ________ provides synchronization without increasing the number of bits.

A) Block coding
B) None of these
C) ________ provides synchronization without increasing the number of bits.
D) All of the above
E) Line coding

73. In Manchester and differential Manchester encoding, the transition at the middle of the bit is used for __________.

A) baud transfer
B) All of the above
C) bit transfer
D) None of these
E) synchronization

74. PCM is an example of _______ conversion.

A) digital-to-digital
B) digital-to-analog
C) analog-to-digital
D) analog-to-analog
E) None of these

75. The data rate is sometimes called the ___ rate.

A) signal
B) None of these
C) All of the above
D) bit
E) baud

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