Exercises 21 through 25 are based on the above situation.
21.
The first two intermediate frequencies in the FMFB receiver have fixed bandwidths, and the third IF has a
variable bandwidth. This variable bandwidth is attained by
a.
varying the frequency of the second VCO.
b.
applying an AGC voltage to the 60-MHz IF amplifier.
c.
placing different resistance values across the third mixer's tank circuit.
d.
permitting the limiter to operate on both positive and negative alternations.
22.
The stage that converts the IF signal into a usable baseband frequency output is the
a.
AGC detector-amplifier.
c.
video amplifier.
b.
differential amplifier.
d.
discriminator.
23.
Compression of the FM signal's deviation to improve the output signal-to-noise ratio is accomplished by
the
a.
regenerative feedback developed in the AFC loop.
b.
degenerative feedback developed in the AFC loop.
c.
degenerative feedback developed in the FMFB loop.
d.
regenerative feedback developed in the FMFB loop.
24.
What is gained by reducing the effective bandwidth of the 800-kHz IF signal?
a.
Reduction of noise power applied to the discriminator
b.
Increase of signal power applied to the discriminator
c.
Reduction in the carrier-to-noise ratio applied to the limiter
d.
Increase in the frequency deviation of the FM signal applied to the limiter
25.
When the discriminator does NOT provide an output for coupling to the differential amplifier, the
differential amplifier causes the second mixer's injection voltage to be at a frequency of
a.
0.8 MHz.
c.
35.2 MHz.
b.
10.8 MHz.
d.
49.2 MHz.
CHECK YOUR ANSWERS WITH LESSON 3 SOLUTION SHEET PAGE 137
344 L3
136
Previous Page
