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1. 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

2. What section of a superheterodyne receiver determines the receiver's bandwidth and selectivity?

a) Preselector
b) IF Amplifier
c) Detector
d) Audio Amplifier
e) None of the above

3. What is the first step that must take place in receiving a radio signal?

a) Select (Tune desired carrier frequency)
b) Demodulate (Detect)
c) Amplify RF Signal
d) Acquire an RF signal

4. What section of a superheterodyne receiver is responsible for attenuation of the image frequency?

a) Detector
b) Preselector
c) Local Oscillator
d) None of these

5. 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

6. Another name for demodulation is:

a) Selection
b) Acquisition
c) Detection
d) None of these

7. What is the name of the amplifier that operates at a constant frequency in a superhet receiver?

a) The audio amplifier
b) The RF amplifier
c) The IF amplifier
d) None of these

8. A mixer has two frequencies being applied, 700 KHz and 1000 KHz. Which of these gives the ideal output frequencies?

a) 700 KHz, 1000 KHz
b) 700 KHz, 1000 KHz, 1700 KHz
c) 700 KHz, 1000 KHz, 1700 KHz, 300 KHz
d) None of these

9. 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

10. 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

11. What two signals should be compared by a technician to determine whether or not a PLL is in lock?

a) The VCO output and the REFERENCE
b) The VCO output and the unfiltered output from the PHASE DETECTOR
c) The REFERENCE and the LOW-PASS FILTER output
d) None of the above

12. 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

13. How can a technician determine that a PLL is in lock?

a) Check that Vcontrol = Vcc/2
b) Check that Fvco = Fref
c) Check that Fvco = Fref / 2
d) None of the above

14. 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

15. When no input signal is being applied to a PLL, what state will it be in?

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

16. How many significant PAIRS of sidebands will be produced by an FM transmitter that is producing 1 KHz of deviation with a 5 KHz deviation rate (information frequency)?

a) 2
b) 1
c) 4
d) None of the above

17. 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

18. An FM transmitter is producing 45 KHz of deviation; the information signal is 5 KHz, 10 Vpk. What will happen to the deviation if the information signal is changed to 5 Vpk?

a) The deviation will become 37 KHz
b) The deviation will become 22.5 KHz
c) The deviation will become 75 KHz
d) None of the above

19. An FM transmitter is producing 20 KHz of deviation with 1Vpk, 10 KHz information signal. What will happen to the deviation if the information signal is changed to 2Vpk?

a) The deviation will increase to 75 KHz
b) The deviation will decrease to 10 KHz
c) The deviation will increase to 40 KHz
d) None of the above

20. How many significant PAIRS of sidebands will be produced by an FM transmitter that is producing 2 KHz of deviation with a 1 KHz deviation rate (information frequency)?

a) 2
b) 1
c) 3
d) 4

21. A certain FM transmitter is operating on 29.600 MHz; the unmodulated carrier voltage Vc = 50 V. The antenna (load) resistance is 50 Ohms. The maximum permitted deviation is 5 KHz. What power will be delivered to the antenna at 100% modulation?

a) 25 Watts
b) 75 Watts
c) 50 Watts
d) 100 Watts

22. An FM transmitter is operating on 49.860 MHz. Fm = 5 KHz and the deviation is 5 KHz. The unmodulated carrier voltage is 1V. The information voltage is 3Vpk. What MINIMUM information voltage will cause the 49.860 frequency component (as viewed on a spectrum analyzer) to become ZERO?

a) 3.24 Vpk
b) 5.00 Vpk
c) 7.20 Vpk
d) None of the above

23. A certain FM transmitter is operating on 29.600 MHz; the unmodulated carrier voltage Vc = 50 V. How much bandwidth will this transmitter occupy if Fm = 1 KHz and the deviation is 1 KHz? (Use a Bessel table, not Carson's rule).

a) 2 KHz
b) 6 KHz
c) 8 KHz
d) 16 KHz
e) None of the above

24. What is the maximum deviation permitted for FM broadcasts in the USA?

a) 50 KHz
b) 150 KHz
c) 25 KHz
d) 75 KHz

25. What type of the transmitters convert input (information) amplitude changes into output carrier frequency changes?

a) FM
b) AM
c) PM
d) None of the above

26. 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

27. Why is it possible to amplify FM signals in a class C amplifier?

a) The maximum power is no more than twice the unmodulated power
b) The power in an FM signal is constant
c) The bandwidth of FM signals quite small, less than 10 KHz
d) None of the above

28. What type of FM transmitter is pictured above?

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

29. Which class of amplifier is generally preferred for power amplification in FM transmitters?

a) A
b) B
c) C
d) None of the above

30. Ideally, an FM transmitter converts:

a) Voltage to Frequency
b) Voltage to Current
c) Frequency to Voltage
d) None of the above

For Exam 3, come prepared to draw a block diagram of a typical superheterodyne receiver, showing typical spectrograms at each of the RF test points. You will also need to be able to design a direct-synthesis PLL at the block diagram level (calculating Fref, Fnatural, N (divisor range), and R (reference divisor). For FM spectral analysis, a Bessel chart will be provided on the last page of the test. You may also use BESSEL.85P (TI85/86) during the test.

Grade Exam!