16
2-42. Phase-shift keying is most useful under
which of the following code element
conditions?
1. When mark elements are longer than
space elements
2. When mark elements are shorter than
space elements
3. When mark and space elements are the
same length
4. When mark and space elements are
longer than synchronizing elements
2-43. When a carrier is phase-shift keying
modulated, (a) a data bit ONE will
normally cause the carrier to shift its phase
what total number of degrees, and (b) a
data bit ZERO will cause the carrier to
shift its phase what total number of
degrees?
1. (a) 60
(b) 0
2. (a) 0
(b) 180
3. (a) 180
(b) 180
4. (a) 180
(b) 0
2-44. Which of the following circuits is used to
generate a phase-shift keyed signal?
1. Logic circuit
2. Phasor circuit
3. Phasitron circuit
4. Longitudinal circuit
2-45. When a carrier is modulated by a square
wave, what maximum number of sideband
pairs will be generated?
1.
1
2.
9
3.
3
4. An infinite number
2-46. As the square wave modulating voltage is
increased to the same amplitude as that of
the carrier, what will be the effect on
(a) the carrier amplitude and (b) amplitude
of the sidebands?
1. (a) Remains constant
(b) Increases
2. (a) Decreases
(b) Increases
3. (a) Increases
(b) Remains constant
4. (a) Increases
(b) Decreases
2-47. In a square-wave modulated signal, total
sideband power is what percentage of the
total power?
1. 0 percent
2. 25 percent
3. 33 percent
4. 50 percent
Figure 2F.—Waveform.
IN ANSWERING QUESTIONS 2-48
THROUGH 2-51, REFER TO FIGURE 2F.
SELECT THE FIGURE LETTER THAT
CORRESPONDS WITH THE WAVEFORM
LISTED IN THE QUESTIONS. LETTERS MAY
BE USED ONCE, MORE THAN ONCE, OR
NOT AT ALL.
2-48. Pulse width.
1. A
2. B
3. C
4. D
