1. In FM reception, the circuitry used to extract the intelligence from the
carrier is:
a. VCO.
b. Crosby modulator.
c. limiter.
d. discriminator.
2. A form of receiver noise called cross modulation is caused by:
a. noise caused by using non-square law device.
b. noise caused by using JFETs.
c. noise caused by the mixer.
d. noise caused by high impedance device.
3. The minimum required voltage for limiting is called:
a. quieting.
b. threshold.
c. limiting knee.
d. all of the above.
4. Which of the following does provide amplitude limiting?
a. ratio detector
b. Foster-Seely discriminator
c. PLL
d. all of the above
5. Input into the PLL is at the:
a. VCO.
b. low-pass filter.
c. phase detector.
d. comparator circuit.
6. The basic difference between the block diagram of an AM receiver
and FM receiver is that:
a. an FM receiver uses a limiter and discriminator instead of a diode
detector.
b. an FM receiver does not use the superheterodyne design.
c. an FM receiver cannot ever use automatic gain control.
d. an FM receiver must use automatic frequency control.
7. A standard IF frequency in FM receivers is:
a. 455 kHz.
b. 4.5 MHz.
c. 9.0 MHz.
d. 10.7 MHz.
8. Why do most quality FM receivers employ FETs in their RF
amplifiers?
a. FETs have a very high input impedance.
b. FETs have a very low input capacitance.
c. FETs have a square-law input/output relationship.
d. FETs have a superior frequency response.
9. The square-law FET characteristics:
a. allow for greater sensitivity in an FM receiver.
b. minimize the cross-modulation distortion in an FM receiver.
c. allow for narrower bandwidth in the tuned amplifier that it is used in.
d. reduces the shot noise produced by the FET.
10. A limiter stage in an FM receiver functions to:
a. limit the amount of frequency deviation in the received FM signal.
b. remove any residual amplitude modulation in the RF signal before
being fed to the detector stage.
c. filter out any cross modulation frequency components produced by the
mixer stage.
d. reduce noise produced by transistors in the RF and IF amplifier stages.
11. Which of the following does not occur in a limiter stage found in an
FM receiver?
a. amplifying a signal with an easily overdriven amplifier
b. clipping action of the FM signal
c. recreating the intelligence signal
d. recreating the FM sinewave due to the flywheel effect
12. The measure of how much signal is required in an FM receiver to
produce a specific level of quieting is referred to as:
a. the receiver's stereo separation.
b. the receiver's noise reduction.
c. the receiver's sensitivity.
d. the receiver's selectivity.
13. Which of the following FM discriminators produces excessive
distortion due to its nonlinear
roll-off characteristics?
a. slope detector
b. Foster-Seely detector
c. ratio detector
d. quadrature detector
e. PLL detector
14. Which of the following FM detectors is a classical design dating back
to vacuum tube technology?
a. quadrature detector
b. Foster-Seely detector
c. PLL detector
d. diode detector
15. The ratio detector design is superior to the Foster-Seely design in
that:
a. amplitude changes in the input FM signal have no effect on the output.
b. it offers superior linear response to wideband FM deviation.
c. it can be built using digital integrated circuits.
d. it uses less diodes than does the Foster-Seely design.
16. The FM detector that can be implemented using digital exclusive-or
gates is the:
a. slope detector.
b. Foster-Seely design.
c. ratio detector.
d. quadrature detector.
e. PLL FM detector.
17. The term "quadrature" in a quadrature detector refers to:
a. the fact that the two input signals to the exclusive-or gate are 90
degrees out of phase with one another.
b. the fact that a four input gate is part of the detector stage.
c. their use in producing four-channel stereo detection.
d. the fact that it was the fourth FM detector design to gain popularity.
18. Which of the following stages is not a building block of a phase-lock
loop?
a. phase comparator
b. frequency multiplier
c. low-pass filter
d. voltage-controlled oscillator
19. A PLL is set up so that its VCO free-runs at 8.9 MHz. The VCO does
not change frequency unless its input is within plus or minus 75 kHz of
8.9 MHz. After it does lock, the input frequency can be adjusted within
plus or minus 120 kHz of 8.9 MHz without having the PLL start to freerun again. The tracking range of the PLL is:
a. 75 kHz.
b. 120 kHz.
c. 150 kHz.
d. 240 kHz.
20. When a PLL is set up as an FM detector, the input FM signal is
applied to the input of:
a. the phase detector of the PLL.
b. the low-pass filter of the PLL.
c. the frequency multiplier of the PLL.
d. the VCO of the PLL.
21. When a PLL is set up as an FM detector, the output intelligence
signal appears at the output of:
a. the phase detector of the PLL.
b. the low pass filter of the PLL.
c. the frequency multiplier of the PLL.
d. the VCO of the PLL.
22. The FM detector design that does not require intricate coil
adjustments to be tuned is the:
a. slope detector.
b. Foster-Seely detector.
c. ratio detector.
d. quadrature detector.
e. PLL detector.
23. In an FM stereo receiver, what is the purpose of the matrix network?
a. to filter out the SCA signal at the output of the discriminator
b. to filter out the L-R signal at the output of the discriminator
c. to filter out the L+R signal at the output of the discriminator
d. to produce separate L and R signals from the L+R and L-R signals
24. In an FM stereo receiver, why is there a frequency doubler stage in
the stereo demodulation section?
a. It doubles the frequency of the L+R audio signals.
b. It doubles the 19 kHz pilot carrier so that the AM detector will work
properly.
c. It is required in the de-emphasis network.
d. It is part of the FM discriminator stage.
25. In an FM stereo receiver, what is the purpose of the AM detector
stage?
a. It converts the L-R DSB signal back into an L-R signal at audio
frequencies.
b. It mixes the L+R and L-R signals to produce separate L and R audio
signals.
c. It converts the L+R DSB signal back into an L+R signal at audio
frequencies.
d. It filters out the 19 kHz pilot carrier from the complex discriminator
output signal.
26. Subscription services that provide industry, department stores, and
restaurants with commercial free background music use what type of
transmission?
a. usually a 67 kHz carrier with 7.5 kHz deviation
b. a third channel frequency multiplexed on the FM modulated signal of
a standard broadcast FM station
c. subsidiary communication authorization
d. all of the above
27. An example of an FM stereo demodulator integrated circuit is the:
a. 3090.
b. 565.
c. 3089.
d. 560.
28. The Bode plot shown in Figure 6-1 is the plot of a:
a. band –stop filter
b. low pass filter
c. band-pass filter
d. high-pass filter
e. none of the above
Figure 6-1
29. The expected output frequency of a mixer circuit with an input
frequency of 92.1 MHz and a local oscillator frequency of 102.8MHz is:
a. 194.9 MHz
b. 10.1 MHz
c. 11.7 MHz
d. 9.7 MHz
e. none of the above