LESSON EXERCISES
In each of the following exercises, select the ONE answer that BEST completes
the statement or answers the question.
Indicate your solution by circling the
letter opposite the correct answers in the subcourse booklet.
1. Assume that the FM receiver shown in figure 153 of TM 11-668 has a first IF
of 4.3 MHz and a second IF of 455 kHz. If the receiver is tuned to a station with
a carrier frequency of 35 MHz, the first and second oscillators may have
frequencies that are, respectively,
a. 4.3 MHz and 455 kHz.
c.
30.7 MHz and 4.755 MHz.
b. 4.755 MHz and 455 kHz.
d.
39.3 MHz and 39.455 kHz.
2. Since the mixing circuits in a radio receiver must have
nonlinear
characteristic responses, the devices that may be used as mixers include
a. pentode electron tubes, crystal diodes, and transformers.
b. triode electron tubes, germanium crystals, and transformers.
c. diode electron tubes, silicon crystals, and resistor networks.
d. diode electron tubes, silicon crystals, and pentode electron tubes.
3. Assume that the mixer tube in an FM receiver has a transconductance of 4,000
micromhos and a plate load impedance of 2,000 ohms at the IF. If the input signal
to the mixer is 320 microvolts and maximum conversion transconductance is reached,
the conversion gain will be
a. less than 2.
c.
between 5 and 10.
b. between 2 and 5.
d.
greater than 10.
4. The local oscillator of a receiver
that is designed to receive signals in the
FM broadcast band (88 MHz to 108 MHz)
has a frequency higher than that of the
incoming signal. To prevent FM signals
within this band from being introduced as
an interfering image signal, the minimum
IF should be approximately
a. 10.7 MHz.
NOTE:
Image frequency = Incoming
signal + (2 x IF).
b. 20.0 MHz.
c. 44.0 MHz.
d. 98.5 MHz.
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