Electrical Engineering · Question Bank

Communications

408 questions · page 20 of 21. Answer in your head first, then check the solution.

#381
Normally, a linear class B RF power amplifier operates with a bias approximately equal to
Atwice cut-off
Bten times cut-off value
C50 % of cut-off value
Dprojected cut-off
#382
The purpose why an RF amplifier is operated under linear class-B conditions (as opposed to class-C) is to
Agenerate only even harmonics
Bgenerate only odd harmonics
Cincrease the efficiency
Damplify an AM signal
#383
The type of emission that suffer most from selective fading.
ACW and SSB
BSSB and TV
CFM and double sideband AM
DSSTV and CW
#384
A receiver selectivity of 10 kHz in the IF circuitry is optimum for what type of signals?
ASSB voice
BFacsimile
CFM
DDouble-sideband AM
#385
In the phasing method of SSB generation, one sideband is canceled out due to
Aphase shifting
Bsharp selectivity
Ccarrier suppression
Dphase inversion
#386
How is a G3E FM-phone signals produced?
AA network consisting modulator on the audio amplifier
BWith a reactance modulator on the final amplifier
CWith a reactance modulator on the oscillator
DWith a balanced modulator on the oscillator
#387
A way of eliminating auto interference to radio reception
AInstalling resistive spark plugs
BInstalling capacitive spark plugs
CInstalling resistors in series with the spark plugs
DInstalling two copper-braid ground strips
#388
A double-sideband phone signal can be generated by
Afeeding a phase-modulated signal into a low-pass filter
Bmodulating the plate voltage of a class-C amplifier
Cusing a balanced modulator followed by a filter
Ddetuning a Hartley oscillator
#389
Cross-modulation in a receiver can be reduced by
Ainstalling a filter at the receiver
Busing a filter at the receiver
Cincreasing the receiver's RF gain while decreasing the AF
Dadjusting the pass-band tuning
#390
What is the cause of receiver desensitizing?
AThe presence of a strong signal on a nearby frequency
BAudio gain adjusted too low
CSquelch gain adjusted too high
DSquelch gain adjusted too low
#391
An RF stage precedes the mixer stage in a superhet receiver. One advantage of including this RF stage is
Abetter selectivity
Bbetter rejection ratio
Cgreater sensitivity
Dimproved signal-to-noise ratio
#392
What is an undesirable effect of using a too-wide filter bandwidth in the IF section of a receiver?
AUndesired signals will reach the audio stage
BOutput-offset overshoot
CThermal-noise distortion
DFilter ringing
#393
A system containing a limiter stage, a discriminator, and a de-emphasis circuit?
ADirect FM transmitter
BIndirect FM transmitter
CSingle sideband AM receiver
DFM receiver
#394
The limiter stage of an FM receiver
Aprevents any amplitude modulation of the IF signal
Blimits the amount of frequency deviation in the IF signal
Climits the overall bandwidth of the IF stages
Dcorrects any deviation in carrier frequency
#395
High selectivity occurs when the degree of coupling between a receiver's RF stages is
Atight
Bloose
Ccritical
Dadjusted for maximum power transfer
#396
A carrier is phase modulated by a test tone. If the amplitude and the frequency of the tone are both doubled, the amount of the deviation is
Adoubled
Bunchanged
Chalved
Dmultiplied by four
#397
The degree of selectivity desirable in the IF circuitry of a single-sideband receiver.
A1 kHz
B2.4 kHz
C4.2 kHz
D4.8 kHz
#398
The base in an RF amplifier is grounded in order to
Aavoid the requirement of neutralizing the stage
Braise the input impedance
Clower the output impedance
Dobtain maximum power output
#399
The AM detector performs two basic functions in the receiver.
ARectifies and filters
BAmplifiers and filters
CBuffer and amplifier
DBuffer and detector
#400
A varactor diode can be used in a/an
Adirect FM modulator circuit
BAFC circuit in a direct FM transmitter
Cphase-modulator circuit
Dall of these

More Electrical Engineering topics