Chapter 2. Amplitude Modulation: Transmission
1. In a modulated system, the low-frequency intelligence signal is not called the
a. Modulating signal
b. Information signal
c. Modulating wave
d. Carrier
2. A 7.0-Mhz carrier is modulated by a voice signal that has three frequency components of 100 Hz,
200 Hz, and 300 Hz. What three frequencies comprise the lower sideband?
a. 6.9997 Mhz, 6.9998 Mhz, and 6.9999 Mhz
b. 100 Hz, 200 Hz, and 300 Hz
c. 6.9999 Mhz, 7.0000 Mhz, and 7.0001 Mhz
d. 7.0001 Mhz, 7.0002 Mhz, and 7.0003 Mhz
3. The total output power of an AM transmitter is measured to be 850 W. What is the total output sideband
power if it has a percent modulation of 100%?
a. 425 W
b. 850 W
c. 283.3 W
d. 141.65 W
4. A 100-kHz carrier is modulated by a 20-Hz – 2kHz signal. The upper sideband is
a. 102 kHz
b. 100.02 kHz to 102 kHz
c. 101 kHz
d. 100.002 kHz to 102 kHz
5. One full revolution of a phasor generates which percentage of a full sinewave?
a. 25%
b. 50%
c. 100%
d. 200%
6. An AM waveform at maximum is 100 V p-p and at minimum is 40 V p-p. The modulation percentage is
a. 250%
b. 40%
c. 25%
d. 37.5%
7. A transmitter having a 900-W carrier transmits 1188 W when modulated with a single sinewave. If the carrier is simultaneously modulated with another sinewave at 60% modulation, calculate the total transmitted power.
a. 1084 W
b. 1170 W
c. 1350 W
d. 1224 W
8. Low-level modulation is
a. The most economic approach for low-power transmitters.
b. Characterized by the use of "linear" power amplifiers to amplify the AM signal.
c. Characterized by having the carrier and the intelligence signals mix at low power levels
d. All the above.
9. The main advantage of a high-level modulation system compared to a low-level system is that it
a. Allows more efficient amplification.
b. Allows use of low-powered intelligence signal.
c. Provides higher modulation percentage.
d. Is more economical.
10. What is the purpose of a buffer amplifier stage in a transmitter?
a. It prevents transmitters from producing spurious frequencies in the output signals.
b. It provides power amplification with high efficiency.
c. Its high input impedance prevents oscillators from drifting off frequency.
d. It amplifies audio frequencies before modulation occurs.
11. The purpose of an antenna coupler is to
a. Match the output impedance of the transmitter with the antenna's impedance to provide maximum
power transfer.
b. Allow the transmitter to be connected to several antennas at the same time.
c. Filter out the carrier frequency from the transmitter's AM output signal.
d. Cause the transmitter to operate at more than one carrier frequency at the same time.
12. The main reason for using a dummy antenna is to
a. Prevent damage to output circuits.
b. Minimize damage to the regular antenna.
c. Prevent overmodulation.
d. Prevent undesired transmissions.
13. A spectrum analyzer is
a. An instrument that displays amplitude versus frequency on a CRT.
b. Often used to determine if a transmitter's output signal is free from any spurious signals.
c. Can be thought of as a radio receiver with broad frequency range.
d. All the above.
14.The strategy for repair of electronic equipment includes the following.
a. Verify that a problem exists.
b. Isolate the defective stage.
c. Isolate the defective component.
d. Replace the defective component and hot check.
e. All the above.
15. A technique that helps you understand how a carrier and sideband combine to form the AM waveform
is
a. The tangential method.
b. Phasor representation.
c. Keying.
d. None of the above.Answers:
D |
A |
C |
B |
C |
D |
C |
D |
A |
C |
A |
D |
D |
D |
B |
solution for the math practice problem...pls.....
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