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1. Which of these describes demodulation?

a) Recovering information from a carrier wave
b) Placing information onto a carrier wave
c) Controlling the frequency of a carrier wave
d) None of the above

2. What is the wavelength of a 600 MHz signal?

a) 1 Meter
b) 0.5 Meter (50 cm)
c) 0.75 Meter
d) None of the above

3. In troubleshooting a stage in an electronic device, where is the best place to check the power supply?

a) At the output terminal of the voltage regulator IC
b) Directly at the terminals of the device using the power
c) At the power supply buss line
d) None of the above

4. What is the frequency of the 3rd harmonic for the signal above?

a) 1 KHz
b) 2 KHz
c) 3 KHz
d) None of these

5. What type of wave is pictured in the spectrogram above?

a) Pure sine wave
b) Square wave
c) Triangle wave
d) None of the above

6. The frequency-domain picture of an electronic signal is called a:

a) Spectrogram
b) Oscillogram
c) Noise Plot
d) None of the above

7. What signal to noise ratio, in dB, will result if a system has 1 mW of noise and 100 mW of signal power?

a) 10 dB
b) 20 dB
c) 30 dB
d) None of the above

8. Which of these could be classified as an external noise source?

a) Shot Noise
b) Atmospheric noise
c) Flicker Noise
d) None of the above

9. What signal to noise ratio, in dB, will result if a system has 1 mV of noise and 1000 mV of signal voltage?

a) 10 dB
b) 20 dB
c) 60 dB
d) None of the above

10. A certain AM transmitter produces 16W of power into a 50 Ohm load with no modulation. What total power will be produced at 50% modulation?

a) 17 W
b) 18 W
c) 20 W
d) None of the above

11. What is the total bandwidth of the AM signal pictured above?

a) 500 Hz
b) 1 KHz
c) 2 KHz
d) 4 KHz

12. What is the total bandwidth of the AM signal pictured above?

a) 2 KHz
b) 700 KHz
c) 10 KHz
d) None of the above

13. What is the percentage of modulation for the AM signal above?

a) 50%
b) 60%
c) 70.7%
d) None of the above

14. New frequencies that are generated during the process of modulation are known as:

a) Harmonics
b) Fundamentals
c) Sidebands
d) None of the above

15. Which of these is an important property for a modulator stage to have?

a) High voltage gain
b) High power gain
c) Low input-impedance
d) Non-linear transfer characteristic

16. What is the function of an RF bypass capacitor?

a) To couple signal from one stage to the next
b) To couple RF energy into the antenna
c) To force RF energy to go to ground
d) None of the above

17. Where would one expect to find an RF bypass capacitor connected within a radio transmitter?

a) Between the final PA stage and the antenna
b) Between the oscillator and buffer amplifier
c) Between a power supply line and ground
d) None of the above

18. What is meant by the term "dead-keyed?"

a) The unmodulated condition; 0% modulation
b) 50% modulated
c) 100% modulated; maximum output power
d) None of the above

19. The oscillator in a certain transmitter produces 1 mW of output. The signal is subsequently amplified in the following stages:

Buffer: +10 dB
Modulator: +6 dB
Driver: +10 dB
Final: +13 dB

What is the final output power of this transmitter in Watts?

a) 8 Watts
b) 4 Watts
c) 400 mW
d) None of these

20. What is the purpose of a buffer amplifier?

a) To provide a large voltage gain
b) To isolate the oscillator from the next stage
c) To reduce distortion of the carrier sine wave
d) None of the above

21. What type of oscillator is pictured above?

a) Colpitts
b) Hartley
c) Armstrong
d) Pierce
e) None of the above

22. Which of these devices would provide the most stable oscillation frequency?

a) An RC time-constant
b) An LC resonant circuit
c) A quartz crystal
d) A ceramic resonator

23. What is the operating frequency of the oscillator pictured above?

a) 599.412 KHz
b) 847.697 KHz
c) 455.000 KHz
d) None of the above

24. Another name for the parallel-resonant frequency of a crystal is the:

a) Pole
b) Zero
c) Maximum
d) Minimum

25. Another name for the series-resonant frequency of a crystal is the:

a) Pole
b) Zero
c) Maximum
d) Minimum

26. A certain crystal has the following characteristics: Ls=1 H, Cs=.001 pF, Rs = 150 Ohms, Cm = 5 pF. What is the series-resonant frequency of the unit?

a) 5.032921 MHz
b) 4.986123 MHz
c) 5.033424 MHz
d) None of the above

27. A certain crystal has the following characteristics: Ls=1 H, Cs=.001 pF, Rs = 150 Ohms, Cm = 5 pF. At parallel-resonance, what is the approximate terminal impedance of the unit?

a) 30 + j125 Ohms
b) 30 - j150 Ohms
c) 150 Ohms (Equal to Rs)
d) Infinity (Open Circuit)

28. A certain crystal has the following characteristics: Ls=1 H, Cs=.001 pF, Rs = 150 Ohms, Cm = 5 pF. At series-resonance, what is the approximate terminal impedance of the unit?

a) 30 + j125 Ohms
b) 30 - j150 Ohms
c) 150 Ohms (Equal to Rs)
d) Infinity (Open Circuit)

29. The ability of the preselector and local oscillator stages to keep a constant difference of F(if) in a superhet receiver is referred to as:

a) AGC
b) Detection
c) Alignment
d) Tracking

30. In a superhet receiver, the difference between the preselector and local oscillator frequencies should always be:

a) The IF frequency
b) The carrier frequency
c) One-half the local oscillator frequency
d) None of these

31. Which of the following specifies the most sensitive receiver? All the units have the same bandwidth. Hint: Convert all into absolute power units.

a) 1 uV into 75 Ohms for better than 10 dB S/N ratio
b) 0.5 uV into 50 Ohms for better than 10 dB S/N ratio
c) -120 dBm for better than 10 dB S/N ratio
d) -110 dBm for better than 10 dB S/N ratio

32. What is meant by the term "high-side injection?"

a) The local oscillator operates with a large AC output signal
b) The IF amplifier uses negative-bias to produce AGC
c) The local oscillator operates above the frequency of the RF carrier
d) None of the above

33. How is a mixer forced to be nonlinear?

a) One frequency applied is higher than the other
b) It is driven into large-signal mode by one of the signal sources
c) The power supply to the mixer is made as large as possible
d) None of these

34. What is the function of the preselector in a superhet receiver?

a) Boosts the gain of the IF amplifier
b) Used to produce the AGC control signal
c) Eliminates the image frequency
d) None of these

35. In the PLL pictured above, the following measurements were made:

F1 = 10.000 MHz
"A" = 100 KHz (5 Vpp square wave)
"B" = 90 KHz (5 Vpp square wave)
VCO Control Voltage = 7.9 V (Steady DC); Vcc = 8.0 V
"D" = 118.536 MHz (Unstable; this is an average).

It is known that R = 100 and N = 1001 from the service documentation. What is the most likely fault in the loop?

a) The N divider is defective (Not triggering correctly on VCO signal)
b) The R divider is defective (Not producing correct frequency at TP "A")
c) The VCO is defective (Not oscillating)
d) The phase detector is defective (Not comparing "A" and "B")
e) The loop is operating correctly

36. When the REFERENCE and VCO frequencies are equal, what state is a PLL in?

a) Free-Running
b) Capture
c) Lock
d) None of the above

37. Given that N=2442, R=10240, and F1 = 10.240 MHz, what will the output frequency Fout of the PLL synthesizer above be?

a) 1.024 MHz
b) 20.480 MHz
c) 8.192 MHz
d) 2.442 MHz

38. Which part of a PLL converts voltage changes into frequency changes?

a) Phase Detector
b) Low Pass Filter
c) VCO
d) None of the above

39. What is the percentage modulation of an FM broadcast transmitter producing 50 KHz deviation?

a) 67%
b) 50%
c) 25%
d) None of the above

40. An FM transmitter is producing 45 KHz of devation; the information signal is 5 KHz, 10 Vpk. What is the modulation index?

a) 9.0
b) 4.5
c) 0.6
d) None of the above

41. What is the total bandwidth allocated for an FM broadcast station in the USA (Including guard bands)?

a) 200 KHz
b) 150 KHz
c) 75 KHz
d) None of the above

42. What is the approximate (CARSON'S RULE) bandwidth of an FM transmitter with a deviation of 2 KHz and information frequency of 15 KHz?

a) 4 KHz
b) 30 KHz
c) 34 KHz
d) None of the above

43. What value should N have in the figure above to get an output frequency of 91.900 MHz? F1=10.000 MHz and R=100.

a) 9190
b) 5620
c) 919
d) 867
e) None of the above

44. What type of FM transmitter is pictured above?

a) Armstrong WBFM
b) PLL
c) Crosby Frequency-Locked-Loop
d) None of the above

45. A 5 MHz crystal oscillator is being driven so that it has 1000 Hz of deviation. This signal is fed into an X3 frequency multiplier. What is the resultant output frequency and deviation?

a) Fout=3 MHz, Deviation=2 KHz
b) Fout=5 MHz, Deviation=3 KHz
c) Fout=15 MHz, Deviation=1 KHz
d) None of the above

46. What type of FM transmitter is pictured above?

a) Armstrong WBFM
b) PLL
c) Crosby Frequency-Locked-Loop
d) None of the above

47. What stage in an FM receiver rejects amplitude disturbances?

a) Detector
b) Limiter
c) Mixer
d) Preselector

48. Which of these FM detectors rely on a closed loop that "follows" the instantaneous frequency changes of the incoming carrier signal?

a) Quadrature
b) Foster-Seeley
c) Ratio
d) PLL
e) None of these

49. An FM detector can be ideally viewed as a/an:

a) Frequency to voltage converter
b) Voltage to frequency converter
c) Amplitude to current converter
d) None of the above

50. What is the purpose of a LIMITER in an FM receiver?

a) Rejects the image frequency
b) Converts the carrier down to the IF frequency
c) Removes amplitude variations
d) None of the above

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