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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. 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

3. 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

4. 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

5. 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

6. 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

7. 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

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

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

9. 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

10. In order for an oscillator to start, the loop gain must be:

a) Greater than 1
b) Greater than or equal to 1
c) Less than 1
d) 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 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)

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

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

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

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

16. What is the bandwidth of the amplifier above?

a) 50 KHz
b) 100 KHz
c) 10.6 KHz
d) None of the above

17. What is the center frequency of the amplifier above?

a) 262 KHz
b) 411 KHz
c) 900 KHz
d) None of the above

18. What power output is available from the amplifier above?

a) 2 mW
b) 4 mW
c) 8 mW
d) None of the above

19. What power output is available from the amplifier above?

a) 6.6 mW
b) 10 mW
c) 5 mW
d) None of the above

20. Using the topology shown above, what value should be used for L1 if a center frequency of 400 KHz with a bandwidth of 10 KHz is desired? The load resistance is 10K Ohms.

a) 198 uH
b) 99.4 uH
c) 22 nH
d) 470 nH
e) None of these

21. What is the image resistance RI of the network above if RL=50 Ohms, XC2=25 Ohms, XC1=30 Ohms, XL=50 Ohms?

a) 50 Ohms
b) 10 Ohms
c) 7.5 Ohms
d) 100 Ohms
e) None of the above

22. When designing a PI (or other matching network) at moderate to high power levels, what is an appropriate design measure?

a) Obtain actual component data for the inductor and capacitors to determine their ESR/Q factors
b) Design for a right-hand Q of at least 4
c) Make sure the right-hand and left-hand Q factors are within at 20% of each other
d) None of the above

23. If R'L is 10 Ohms and Vcc=12 V, what CW power output will be produced by the unit pictured above?

a) 10 W
b) 7.2 W
c) 25 W
d) None of the above

24. If Vcc=10 V, what voltage can be expected at test point A in a properly-operating unit?

a) 20Vp-p
b) 10Vp-p
c) 5Vp-p
d) None of the above

25. If Vcc=12V and R'L is 5 Ohms in the figure above, what audio input power will be needed to obtain 100% modulation?

a) 14.4 W
b) 28.8 W
c) 7.2 W
d) None of the above

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