13
2-21. The spectrum of a 500 kilohertz fm-
modulated carrier has a 60-kilohertz
bandwidth and contains 12 significant
sidebands. How much, in kilohertz, is the
carrier deviated?
1. 5
2. 7.5
3. 10
4. 15
2-22. In a reactance-tube modulator, the
reactance tube shunts what part of the
oscillator circuitry?
1. The amplifier
2. The tank circuit
3. The biasing network
4. The feedback network
2-23. With no modulating signal applied, a
reactance tube has which, if any, of the
following effects on the output of an
oscillator?
1. It will decrease amplitude
2. It will increase amplitude
3. It will change resonant frequency
4. It will have no effect
2-24. The reactance-tube frequency modulates
the oscillator by which of the following
actions?
1. By shunting the tank circuit with a
variable resistance
2. By shunting the tank circuit with a
variable reactance
3. By shunting the tank circuit with a
variable capacitance
4. By causing a resultant current flow in
the tank circuit which either leads or
lags resonant current
Figure 2C.—Semiconductor reactance modulator.
IN ANSWERING QUESTIONS 2-25 AND 2-26,
REFER TO FIGURE 2C.
2-25. The semiconductor reactance modulator in
the circuit is in parallel with a portion of
the oscillator tank circuit coil. Modulation
results because of interaction with which
of the following transistor characteristics?
1. Collector-to-emitter resistance
2. Collector-to-emitter capacitance
3. Base-to-emitter resistance
4. Base-to-emitter capacitance
2-26. With a positive-going modulating signal
applied to the base of Q2, (a) what will
circuit capacitance do and (b) what will
the output frequency do?
1. (a) Decrease
(b) decrease
2. (a) Decrease
(b) increase
3. (a) Increase
(b) increase
4. (a) Increase
(a) decrease
