1. The FM modulation index:
a. | increases with both deviation and modulation frequency |
b. | increases with deviation and decreases with modulation frequency |
c. | decreases with deviation and increases with modulation frequency |
d. | is equal to twice the deviation |
ANS: B
2. One way to derive FM from PM is:
a. | integrate the modulating signal before applying to the PM oscillator |
b. | integrate the signal out of the PM oscillator |
c. | differentiate the modulating signal before applying to the PM oscillator |
d. | differentiate the signal out of the PM oscillator |
ANS: A
3. The bandwidth of an FM signal is considered to be limited because:
a. | there can only be a finite number of sidebands |
b. | it is equal to the frequency deviation |
c. | it is band-limited at the receiver |
d. | the power in the outer sidebands is negligible |
ANS: D
4. Mathematically, the calculation of FM bandwidth requires the use of:
a. | ordinary trigonometry and algebra | c. | Taylor series |
b. | Bessel functions | d. | fractals |
ANS: B
5. FM bandwidth can be approximated by:
a. | Armstrong's Rule | c. | Carson's Rule |
b. | Bessel's Rule | d. | none of the above |
ANS: C
6. NBFM stands for:
a. | National Broadcast FM | c. | Near Band FM |
b. | Non-Broadcast FM | d. | Narrowband FM |
ANS: D
7. When FM reception deteriorates abruptly due to noise, it is called:
a. | the capture effect | c. | the noise effect |
b. | the threshold effect | d. | the limit effect |
ANS: B
8. An FM receiver switching suddenly between two stations on nearby frequencies is called:
a. | the capture effect | c. | the "two-station" effect |
b. | the threshold effect | d. | none of the above |
ANS: A
9. Pre-emphasis is used to:
a. | increase the signal to noise ratio for higher audio frequencies |
b. | increase the signal to noise ratio for lower audio frequencies |
c. | increase the signal to noise ratio for all audio frequencies |
d. | allow stereo audio to be carried by FM stations |
ANS: A
10. A pre-emphasis of 75 ms refers to:
a. | the time it takes for the circuit to work |
b. | the "dead time" before de-emphasis occurs |
c. | the time delay between the L and R channels |
d. | the time-constant of the filter circuits used |
ANS: D
11. FM stereo:
a. | uses DSBSC AM modulation | c. | has a higher S/N than mono FM |
b. | is implemented using an SCA signal | d. | is not compatible with mono FM |
ANS: A
12. An SCA signal:
a. | can use amplitude modulation | c. | is monaural |
b. | can use FM modulation | d. | all of the above |
ANS: D
13. The modulation index of an FM signal can be determined readily:
a. | using measurements at points where J0 equals one |
b. | using measurements at points where J0 equals zero |
c. | using measurements at points where the deviation equals zero |
d. | only by using Bessel functions |
ANS: B
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