14
2-27. What type of circuit is used to remove the
AM component in the output of a
semiconductor reactance modulator?
1. A mixer
2. A filter
3. A limiter
4. A buffer amplifier
Figure 2D.—Multivibrator modulator.
IN ANSWERING QUESTIONS 2-28 AND 2-29,
REFER TO FIGURE 2D.
2-28. The multivibrator modulator produces fm
modulation by which of the following
actions?
1. By modulating the collector voltages
2. By modulating the base-return voltages
3. By modulating the value of the base
value of the base capacitors
4. By modulating the value of the base
resistors
2-29. What is the purpose of the filter on the
output of the multivibrator modulator?
1. To establish the fundamental operating
frequency
2. To eliminate unwanted frequency
variations
3. To eliminate unwanted odd harmonics
4. To eliminate unwanted even harmonics
2-30. A multivibrator frequency modulator is
limited to frequencies below what
maximum frequency?
1. 1 megahertz
2. 2 megahertz
3. 5 megahertz
4. 10 megahertz
2-31. To ensure the frequency stability of an fm
transmitter, which, if any, of the following
actions could be taken?
1. Modulate a crystal-controlled oscillator
at the desired frequency
2. Modulate a low-frequency oscillator,
and use frequency multipliers to
achieve the operating frequency
3. Modulate a low-frequency oscillator,
and heterodyne it with a higher-
frequency oscillator to achieve the
desired frequency
4. None of the above
2-32. A varactor is a variable device that acts as
which of the following components?
1. Resistor
2. Inductor
3. Capacitor
4. Transistor
2-33. As the positive potential is increased on
the cathode of a varactor, (a) what happens
to reverse bias and (b) how is dielectric
width affected?
1. (a) Increases (b) increases
2. (a) Increases (b) decreases
3. (a) Decreases (b) decreases
4. (a) Decreases (b) increases
