EST

1. The theory of radio waves was iriginated by?

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

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

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

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

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

4. Distortion is caused by:

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

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

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

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

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

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

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

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

A) signal voltage divided by noise voltage
B) None of these
C) first add the signal power to the noise power, then divide by noise power
D) signal power divided 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 the channel
C) signal-to-noise ratio in dB
D) how much noise is in a communications system
E) how much noise an amplifier adds to a signal

10. SINAD is calculated as:

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

11. The UHF band starts at ____________________ MHz.

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

12. The VHF band starts at ____________________ MHz.

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

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

A) spectrum domain monitor
B) spectrum signal monitor
C) None of these
D) spectrum displayer
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) 30 μV
B) 60 μV
C) None of these
D) 50 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) None of these
B) 50 dB
C) 40 dB
D) 30 dB
E) 20 dB

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

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

17. The "Miller Effect" can:

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

18. The Miller Effect can be avoided by:

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

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

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

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

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

21. Generally, conductor lengths in RF circuits should be

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

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

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

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

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

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

A) 5.4 μH
B) 6.4 μH
C) 6.2 μH
D) None of these
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) of None these
B) 1000
C) 100
D) 10
E) 500

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) 0.5
C) 0.3
D) None of these
E) 0.2

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

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

28. AM stands for:

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

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

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

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

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

31. As compared to plain AM, SSB AM:

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

32. The SC in SSB SC stands for:

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

33. The FM modulation index:

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

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

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

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

A) 0.11
B) None of these
C) 0.5
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) 11 kHz
C) 12 kHz
D) None of these
E) 13 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) 68 kHz
C) None of these
D) 50 kHz
E) 48 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) None of these
B) 80%
C) 100%
D) 72%
E) 50%

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

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

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

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

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

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

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

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

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

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

A) 119 MHz
B) None of these
C) 220 MHz
D) 216 MHz
E) 300 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) 250 kHz
B) 40 kHz
C) 61 kHz
D) None of these
E) 191 kHz

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

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

47. Transmitting data as serial binary words is called

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

48. Sampling an analog signal produces

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

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

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

50. The desirable SWR on a transmission line is

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

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

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

52. The impedance of a dipole is about

A) 50 Ω
B) 50 Ω
C) None of these
D) 73 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) 372 W
B) 250 W
C) None of these
D) 483 W
E) 480 W

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

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

55. Which diode is a popular microwave oscillator

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

56. Most satellites operate in which frequency band?

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

57. The main power sources for a satellite are

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

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

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

59. The most widely used data communications code is

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

60. The ASCII code has

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

61. The typical bandwidth of a satellite band is

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

62. The modulation normally used with digital data is

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

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

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

64. Which cable length has the highest attenuation?

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

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

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

66. The wavelength of visible light extends from

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

67. Both LEDs and ILDs operate correctly with

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

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

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

69. The speed of light is

A) None of these
B) 100,000,000 m/s
C) 1,000,000 m/s
D) 200,000,000 m/s
E) 300,000,000 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) bipolar
B) polar
C) unipolar
D) None of these
E) All of the above

71. ______ substitutes eight consecutive zeros with 000VB0VB.

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

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

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

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

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

74. PCM is an example of _______ conversion.

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

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

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

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