12
2-14. A 1,000-hertz tone of a certain loudness
causes the frequency-modulated carrier for
the circuit to vary 1,000 hertz at a rate of
1,000 times per second. If the
AMPLITUDE of the modulating tone is
doubled, what will be the maximum
carrier variation?
1. 1,000 hertz at 1,000 times per second
2. 1,000 hertz at 2,000 times per second
3. 2,000 hertz at 1,000 times per second
4. 2,000 hertz at 2,000 times per second
2-15. The maximum deviation for a 1.5 MHz
carrier is set at 50 kHz. If the carrier
varies between 1.5125 MHz and 1.4875
MHz (12.5 kHz), what is the percentage
of modulation?
1. 25 %
2. 50 %
3. 75 %
4. 100 %
2-16. An fm transmitter has a 50-watt carrier
with no modulation. What maximum
amount of output power will it have when
it is 50-percent modulated?
1. 25 watts
2. 50 watts
3. 75 watts
4. 100 watts
2-17. Frequencies that are located between
adjacent channels to prevent interference
are referred to as
1. sidebands
2. bandwidths
3. guard bands
4. blank channels
2-18. Modulation index may be figured by using
which of the following formulas?
1. 2f/fm
2. fm/2f
3. fm/Df
4. Df/fm
2-19. A 50-megahertz fm carrier varies between
49.925 megahertz and 50.075 megahertz
10,000 times per second. What is its
modulation index?
1. 5
2.
10
3.
15
4.
20
Figure 2B.—Modulation index table.
IN ANSWERING QUESTIONS 2-20 AND 2-21,
REFER TO FIGURE 2B.
2-20. An fm-modulated carrier varies between
925 kilohertz and 1,075 kilohertz 15,000
times per second. What is the bandwidth,
in kilohertz, of the transmitted signal?
(HINT: You will need to figure MI to be
able to find the sidebands.)
1.
340
2.
420
3.
480
4.
560
