c. immunity from undesirable AM signals.
d. good image rejection and adjacent-channel selectivity.
2. Assume that the input circuit of an RF amplifier in an FM receiver has a
resistance of 10,000 ohms. If the receiver is to have a bandwidth of 100 kHz, the
minimum incoming signal that will override the noise and produce a useful receiver
output is approximately
a. 3 microvolts.
c.
10 microvolts.
b. 5 microvolts.
d.
30 microvolts.
3. Assume that you have analyzed the response curve of the RF amplifier in an FM
receiver and found that the response is essentially flat from 101.92 MHz to 102.08
MHz.
If the input circuit resistance is 7,000 ohms, the average input circuit
noise voltage is
a. less than 2 microvolts.
b. between 2 and 3 microvolts.
c. between 3 and 5 microvolts.
d. greater than 5 microvolts.
4. Although the elimination of amplitude variations reduces the noise in an FM
receiver, some interference results from fluctuation noises in the electron tubes.
These noises are caused by variations in the
a. positive-grid currents, size of the space charge, and cathode emission.
b. size of the space charge, cathode emission, and currents induced in the
control grid.
c. cathode emission, currents induced in the control grid, and positive-grid
currents.
d. currents induced in the control grid, positive-grid currents, and size of the
space charge.
5. Assume that the equivalent noise resistance of a given pentode mixer produces
a noise signal of 3.2 microvolts. If the bandpass is to remain about 100 kHz, the
equivalent noise resistance of a hexode mixer would produce a noise signal of
approximately
a. 30 microvolts.
b. 20 microvolts.
c. 10 microvolts.
d. 5 microvolts.
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