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1. 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

2. To isolate a transmitter's carrier oscillator from undesired load changes, what stage is often used?

a) A buffer amplifier
b) A class C amplifier
c) A power amplifier
d) None of the above

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. 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

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 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. 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

8. 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

9. What type of oscillator is pictured above?

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

10. 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

11. 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

12. 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

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

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

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

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

15. 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)

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

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

17. A superhet receiver is using high-side injection. The incoming RF signal has a carrier frequency of 560 KHz; the IF frequency is 455 KHz. What is the image frequency?

a) 1470 KHz
b) 1015 KHz
c) 1120 KHz
d) 1165 KHz
e) None of these

18. 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

19. 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

20. A mixer is producing the following frequency outputs: 710 KHz, 455 KHz, 1165 KHz, 1875 KHz. What are the two most likely frequencies being applied?

a) 710 KHz, 1165 KHz
b) 1875 KHz, 1165 KHz
c) 1000 KHz, 875 KHz
d) 262.5 KHz, 300 KHz
e) None of these

21. 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

22. 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

23. 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

24. 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

25. 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

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