a.
modulating the final amplifier.
b.
using a very stable power supply.
c.
using an oscillator with a very stable frequency.
d.
isolating the oscillator from the final amplifier.
7. The purpose of the AF modulator in the transmitter shown in figure 2-9 is
to vary the amount of plate power of the
a.
AF speech amplifier.
c.
final RF amplifier.
b.
RF buffer amplifier.
d.
RF oscillator.
8.
In figure 2-9, voice signals are changed into voltages by the action of
the
a.
modulator.
c.
speech amplifier.
b.
microphone.
d.
final RF amplifier.
9. In the double-sideband transmitting system, the carrier, USB, and LSB are
transmitted together. The receiver receives all three, and the audio is extracted
by the
a.
RF amplifier.
c.
b.
IF amplifier.
d.
modulator.
10. To develop a given amount of signal power
at
the
receiver,
an
SSB
transmitter is better than a DSB transmitter because it
a.
provides more carrier power and is smaller.
b.
is smaller and uses less of the frequency spectrum.
c.
eliminates the modulator and provides more carrier power.
d.
uses less of the frequency spectrum and eliminates the modulator.
11. The information signal is used to vary either the amplitude or frequency
of the transmitted carrier in a process known as
a.
modulation.
c.
amplification.
b.
demodulation.
d.
12. FM communication channels are located in the VHF or higher frequency
ranges because
a.
outside interference does not introduce noise at higher frequencies.
b.
line-of-sight transmission permits a longer operating range.
309 L2
35
Previous Page
