Your Name: @ 18.97.9.173

1. 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

2. 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

3. 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

4. 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

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

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

6. 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

7. 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

8. The oscillator in a certain transmitter produces +6 dBm of output. The signal is subsequently amplified in the following stages:

Buffer: +10 dB
Modulator: +6 dB
Driver: +10 dB
Final: +14 dB
Antenna Coupler: -1 dB
What is the final output power of this transmitter in Watts?

a) 8 Watts
b) 32 Watts
c) 400 mW
d) None of these

9. 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

10. What type of oscillator is pictured above?

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

11. 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

12. 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

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. 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

15. Another name for the parallel-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. A certain superhet receiver has a preselector bandwidth that averages 100 KHz, and an IF bandwidth of 10 KHz. What will the receiver's total bandwidth be?

a) 10 KHz
b) 110 KHz
c) 210 KHz
d) 150 KHz
e) None of these

18. The two signal components that are produced in a diode-type AM detector circuit are:

a) The upper and lower sidebands
b) A DC level and the AC information signal
c) The carrier frequency and sidebands
d) None of these

19. Another name for demodulation is:

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

20. 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

21. 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

22. Why can't TRF receivers be constructed for high-frequency (above 1-2 MHz) use?

a) Insufficent "Q" is available from discrete LC components at these frequencies
b) Transistors and ICs have insufficient gain at these frequencies
c) Detector circuits produce excessive distortion at these frequencies
d) None of the above

23. 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

24. 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

25. 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

Just a few of the reasons why we're here!

Press GRADE EXAM button to see how you did!

Grade Exam!