EET368 Practice Test II

Instructions: There are 25 questions on this test. It is written in a style very similar to the REAL exam #2. Choose the best answer from among those given. Click the GRADE button on the bottom of the form when you want the exam graded.

Note: You can practice this test as many times as you desire; the system will cook you up a fresh batch of questions each time you access this page -- at least until the NT server dies!

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1. 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

2. 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

3. 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

4. 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

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. Where would one expect to find an RF bypass capacitor connected within a radio transmitter?

a) Between the final PA stage and the antenna
b) Between the oscillator and buffer amplifier
c) Between a power supply line and ground
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 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

9. What type of oscillator is pictured above?

a) Colpitts
b) Hartley
c) Armstrong
d) Pierce
e) 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. 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

14. 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

15. 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)

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

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

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

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

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

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

19. Using the topology shown above, what value of RL would be optimal for a power output of 10 mW if Vcc=8 V?

a) 10K Ohms
b) 50 Ohms
c) 1000 Ohms
d) 2592 Ohms
e) None of these

20. What is the center frequency of the amplifier pictured above?

a) 490 KHz
b) 438 KHz
c) 350 KHz
d) None of the above

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. Where would the network above most likely be found in a transmitter?

a) At the oscillator stage
b) At the modulator stage
c) Between the final PA and antenna
d) None of the above

23. 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

24. If Vcc=14 V, Np=50T, Ns=100T, what input peak voltage is needed to 100% modulate the stage above?

a) 14Vpk
b) 7Vpk
c) 21Vpk
d) None of the above

25. 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

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