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1. Where does the modulation take place at in a high-level transmitter?

a) At the oscillator
b) At the final power amplifier
c) At the buffer amplifier
d) Before the final power amplifier

2. Where does the modulation take place at in a low-level transmitter?

a) At the oscillator
b) At the final power amplifier
c) At the buffer amplifier
d) Before the final power amplifier

3. What class of amplifier would be serve as a modulator?

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

4. What is the purpose of the zener diode in a power supply circuit for an oscillator?

a) To regulate the DC supply of the oscillator, preventing frequency drift
b) To lower the DC supply voltage for the oscillator
c) To eliminate RF currents on the power supply rail
d) None of the above

5. 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

6. 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

7. Why would a class C amplifier be an excellent choice for use as a modulator in a radio transmitter?

a) The class C amplifier generates very low levels of distortion
b) The class C amplifier can operate on very low supply voltages
c) The class C amplifier is very nonlinear -- a requirement for modulation
d) None of the above

8. A certain high-level transmitter produces 10 Watts of carrier power. How much power must the audio amplifier produce to 100% modulate this transmitter?

a) 2 Watts
b) 4 Watts
c) 8 Watts
d) 5 Watts
e) None of the above

9. A certain oscillator has an amplifier with a phase shift of 45 degrees. According to the Barkhausen criteria for oscillation, what phase shift in the FEEDBACK network would be necessary to cause oscillation?

a) 90 Degrees
b) -45 Degrees
c) 315 Degrees
d) (b) or (c)
e) None of the above

10. What type of oscillator is pictured above?

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

11. What type of oscillator is pictured above?

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

12. What type of oscillator is pictured above?

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

13. 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)

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

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

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

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

16. 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)

17. What is meant by the term "low-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

18. 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

19. What is the advantage of having a constant-frequency amplifier (the IF amplifier) in a superheterodyne receiver?

a) The gain can be held constant
b) The noise is minimized
c) The bandwidth will be constant
d) None of these

20. The DC bias for the RF and IF stages in a superheterodyne receiver is derived partly from:

a) The audio power amplifier
b) The 2nd IF amplifier
c) The local oscillator
d) The AM detector
e) None of these

21. 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

22. 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

23. 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

24. The DC component from the AM detector is used for what purpose?

a) To reduce distortion in the audio amplifier
b) To prevent frequency drift in the local oscillator
c) To control the gain of the RF and IF stages (AGC)
d) None of the above

25. Another name for demodulation is:

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

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