c. sharply peaked at 4.7 MHz, and dropping off rapidly at frequencies above
and below.
d. constantly high between 4.625 MHz and 4.775 MHz, and zero below 4.625 MHz
and above 4.775 MHz.
5. Stagger tuning is often employed in IF stages of FM receivers to
a. broaden the response to sideband frequencies and reduce the tendency of
the IF's to oscillate.
b. increase the receiver tuning range and broaden the response to sideband
frequencies.
c. reduce the tendency of the IF's to oscillate and reduce the amount of
phase distortion.
d. reduce the amount of phase distortion and increase the receiver tuning
range.
6. Ideally, the IF amplifier section of an FM receiver will be designed to
produce high gain over a fairly wide band of frequencies and good attenuation of
the adjacent channel signals.
An effective means of providing adjacent-channel
rejection is to use
a. stagger-tuned IF amplifiers.
b. overcoupled IF transformers.
c. resistance-coupled amplifiers preceded by a bandpass filter.
d. critically coupled transformers with double conversion.
7. A transformer-coupled pentode IF stage tends to become unstable and less
selective at high frequencies because of the residual capacitance between the plate
and grid of the tube. This tendency may be reduced by
a. increasing the gain of the stage.
b. replacing the tube with a low-gain triode.
c. connecting
four
capacitors
in
a
bridge
circuit
between
the
grid
and
ground.
d. selecting a capacitor of proper value as a bypass for both screen and
plate circuits.
8. In high-gain IF systems, it is usually necessary to isolate the input circuit
from the output circuit in order to prevent oscillations.
If the IF system has
extremely high gain and wide bandpass requirements, the isolation can be
accomplished with a minimum of added noise by using
a. stray capacitance to tune the plate circuits of the IF stages.
b. transformers with a high ratio of inductance to capacitance.
33
Previous Page
