Chapter 4 Problems

ECET 214Prof. Park

NJIT

Problem 1

SSB transmitters are usually rated in terms of:

a. power gainb. voltage gainc. modulation indexd. peak envelope power

Problem 2

Which of the following is required for SSBtransmission?

a. carrier eliminationb. elimination of one sidebandc. a and bd. none of the above

Problem 3

Which of the following is NOT an advantage that thephase method of generating has over the filtermethod?

a. requires high Q filters.b. lower intelligence frequencies can be used.c. greater ease in switching from one sideband to the

other.d. SSB generated directly at desired transmitting

frequency.

Problem 4

The major disadvantage of the phase method ofSSB generation is:

a. requires two balance modulatorsb. does not use high Q filtersc. 90° phase-shifting network for intelligence

signald. all of the above

Problem 5

Which of the following can be used as an SSBdemodulator?

a. RF amplifierb. audio amplifierc. AGC circuitryd. mixer

Problem 6

At 100% modulation, an AM signal has a totalpower of 1200 watts. If it was converted to SSB andthe sideband component had the same amplitudeas before, the total power would be:

a. 100 wattsb. 200 wattsc. 400 wattsd. 800 watts

Problem 7

The PEP rating of an SSB transmitter is often misleadingdue to:

a. the fact that with normal voice signals, an SSB transmitter develops an average of only one-third to one-fourth of its PEP rating.

b. the SSB transmitter's power supplies and components are not always designed for continuous duty PEP power levels.

c. the PEP rating is the same rating no matter what type of waveform the transmitter is providing.

d. all of the above.

Problem 8

If the carrier and one of the sidebands arecompletely eliminated, the resulting signal isreferred to as:

a. SSB.b. SSBSC.c. ACSSB.d. vestigial sideband.

Problem 9

If the carrier is reduced in amplitude and one ofthe sidebands is completely eliminated, theresulting signal is referred to as:

a. independent sideband.b. SSBSCc. ACSSB.d. vestigial sideband.

Problem 10

The type of sideband that involves having theupper sideband contain different informationthan the lower sideband is referred to as:

a. independent sideband.b. SSBSCc. ACSSB.d. vestigial sideband.

Problem 11

The type of sideband that is used for televisionvideo transmission is called:

a. independent sidebandb. SSBSCc. ACSSBd. vestigial sideband

Problem 12

A more recently developed system of sidebandthat involves compressing the amplitude ofthe intelligence signal before modulation occurs iscalled:

a. independent sideband.b. SSBSC.c. ACSSB.d. vestigial sideband.

Problem 13

The most important advantage of SSB over AM is:

a. that it is a more effective utilization of the available frequency spectrum.

b. that it is less subject to the effects of selective fading.

c. the resulting savings in power.d. simplicity in design.

Problem 14

Which is not an advantage of SSB over AM?

a. SSB provides a more effective utilization of the available frequency spectrum.

b. SSB is less subject to the effects of selective fading.

c. SSB has a resulting savings in power.d. simplicity in design.

Problem 15

The output of a balanced modulator in an SSBtransmitter being modulated with a voiceintelligence signal is:

a. conventional AM.b. SSB.c. DSB-SC.d. a sinewave at the carrier frequency.

Problem 16

Which of the following will not work as abalanced modulator?

a. a dual-gate FET and a band-pass filterb. a push-pull modulatorc. a ring-diode modulatord. an LM1496 integrated circuit stage

Problem 17

In a push-pull modulator, the carrier suppressionis accomplished by:

a. a dual-gate FET having symmetry.b. center-tapped transformers causing canceling

magnetic fields.c. the nonlinearity of the diodes that are used.d. symmetrical differential amplifier stages.

Problem 18

In a linear integrated circuit balanced modulatorsuch as the LM1496, carrier suppression isaccomplished by:

a. center-tapped transformers causing canceling magnetic fields.

b. a dual-gate FET having symmetry.c. the nonlinearity of the diodes that are used.d. symmetrical differential amplifier stages.

Problem 19

Voice transmission requires an audio frequencyrange of:

a. 20 Hz to 20 kHz.b. 30 Hz to 10 kHz.c. 100 Hz to 3 kHz.d. 500 Hz to 1 kHz.

Problem 20

In an SSB transmitter having voice modulation usingaudio frequencies ranging from 100 Hz to 3 kHz, theupper and lower sidebands generated by thebalanced modulator are separated by:

a. 500 Hz.b. 200 Hz.c. 6 kHz.d. 40 Hz.

Problem 21

Calculate the required Q for the bandpassfilter depicted in Figure 4-1 for 80 dBsideband suppression if the carrierfrequency component of the IF is 455 kHz.

a. 1137.5b. 56,875c. 227,500d. 113,750

Problem 22

Crystal filters:

a. have Q values as high as 50,000.b. employ phasing capacitors to produce a

rejection notch of undesired resonant frequencies.

c. are quite delicate in construction.d. all of the above.

Problem 23

Which is not an advantage of ceramic filters overcrystal filters?

a. more rugged in construction.b. smaller in size.c. higher Q values.d. less expensive.

Problem 24

The ratio of the 60 dB and 6 dB bandwidths fora ceramic filter is known as:

a. the shape factor.b. the ripple amplitude.c. the quality factor.d. the roll-off rate of the skirt.

Problem 25

The variation in attenuation within thebandpass frequencies of a ceramic filter iscalled:

a. the shape factor.b. the ripple amplitude.c. the quality factor.d. the roll-off rate of the skirt.

Problem 26

The first designed sharp filter used in SSBtransmitters to produce SSB is the:

a. crystal filter.b. ceramic filter.c. mechanical filter.d. tank circuit.

Problem 27

The filter consisting of resonant disks, driving rods, biasmagnets and transducer coils is the:

a. crystal filter.b. ceramic filter.c. mechanical filter.d. tank circuit.

Problem 28

In Figure 4-2, the filter Qrequired in the linear amplifieris approximately:

a. 20.b. 10.c. 15.d. 100.

Problem 29

In Figure 4-2, the output signalof stage (b) is:

a. DSB-SC at 500 kHz.b. DSB-SC at 10 MHz.c. SSB at 500 kHz.d. SSB at 10 MHz.

Problem 30

In Figure 4-2, the output signalof stage (d) is:

a. DSB-SC at 500 kHz.b. DSB-SC at 10 MHz.c. SSB at 500 kHz.d. SSB at 10 MHz.

Problem 31In Figure 4-2, the first mixerand filter are necessary to:

a. produce SSB at the final transmitter output frequency.

b. produce SSB using filters having adequately high Q values.

c. produce DSB-SC at the final transmitter output frequency.

d. produce DSB-SC using filters having adequately high Q values.

Problem 32In Figure 4-2, the secondmixer and filter are necessaryto:

a. produce SSB at the final transmitter output frequency.

b. produce SSB using filters having adequately high Q values.

c. produce DSB-SC at the transmitter output frequency.

d. produce DSB-SC using filters having adequately high Q values.

Problem 33

In Figure 4-3, the purpose of Q1 and Q2 are to:

a. mix the carrier with the intelligence signal to produce DSB-SC.

b. amplify the carrier signal.c. filter out one of the sidebands.d. amplify the audio intelligence signals.

Problem 34

In Figure 4-3, the required push-pull action of Q1 andQ2 is furnished by:

a. the balance potentiometer, R2.b. the transformer, T1.c. the fact that one of them is a common gate amplifier

and the other is a common source amplifier.d. the 0.1 μf capacitor that connects their sources

together.

Problem 35

In Figure 4-3, Q4 is needed:

a. to provide gain to the carrier output signal.b. to act as an oscillator to produce a carrier signal.c. to upset the balance of the balanced modulator in

order to produce a carrier output signal.d. to help filter out the undesired sideband.

Problem 36

In Figure 4-3, the 9 MHz crystal filter can produce either USB orLSB due to:

a. its bandwidth being wide enough to filter out both sidebands.b. the 30 pf capacitors across its input and output terminals.c. the IF amplifier transistor, Q3, having sufficiently high

bandwith.d. the carrier frequency being slightly altered to create either

sideband at 9 MHz.

Problem 37

Which is not a general method used to generate SSB intransmitter design?

a. filter methodb. lattice methodc. amplitude-compandoring methodd. phase method

Problem 38

Which is the most popular method used to generateSSB in transmitter design?

a. filter methodb. lattice methodc. amplitude-compandoring methodd. phase method

Problem 39

The main disadvantage of the phase method in generatingSSB is:

a. the complex method of mixing the carrier with the intelligence signal.

b the complex method used to amplify the resulting SSB signal.

c. the complex design of the 90 degree phase shifting network for the intelligence signal.

d. the complex design of the 90 degree phase shifting network for the carrier signal.

Problem 40

ACSSB is:

a. a method of compressing the audio before modulation and to expand it following demodulation.

b. an acronym for amplitude compandored single-sideband.

c. a new method of allowing narrow band voice communications with the performance of FM systems for the land-mobile communication industry.

d. all of the above.

Problem 41

The signal processor that increases all negative dBmpower levels and at the same time decreases allpositive dBm power levels is:

a. a signal expander.b. a linear amplifier.c. a signal compressor.d. a phase-locked loop.

Problem 42

The signal processor that decreases all negativedBm power levels and at the same timeincreases all positive dBm power levels is:

a. a signal expander.b. a linear amplifier.c. a signal compressor.d. a phase-locked loop.

Problem 43

Why is the carrier signal needed in an SSB receiver?

a. It is needed for the receiver to maintain its sensitivity and selectivity.

b. It is needed for the demodulator to be able to recreate the intelligence.

c. The carrier actually contains the intelligence signal.d. Without a carrier, the signal strength of the

received station is zero.

Problem 44

The standard SSB demodulator consists of:

a. an RF amplifier, nonlinear mixer, and IF amplifier stage.

b. a nonlinear diode and a low-pass filter.c. a sharp bandpass filter and an audio amplifier

stage.d. a beat frequency oscillator, nonlinear mixer,

and low-pass filter.

Problem 45

In an SSB receiver, if the BFO drifts slightly off ofthe carrier frequency:

a. the output intelligence is badly distorted.b. the output intelligence amplitude is reduced.c. the noise level increases.d. harmonics are produced by mixing action of

the nonlinear device.

Problem 46

In Figure 4-4, the purpose of stage (b) is:a. to demodulate the 20 MHz USB signal.b. to create a 1 MHz SSB IF signal.c. to recreate the 100 Hz to 3 kHz intelligence signal.d. to act as a product detector.

Problem 47

In Figure 4-4, what stages have tracking capacitors?a. stages d and fb. stages d and ec. stages b and ed. stages a and c

Problem 48

In Figure 4-4, what frequency must the BFO be set at for optimum results?

a. 455 kHzb. 20 MHzc. 1 MHzd. 21 MHz

Problem 49

In Figure 4-4, most of the selectivity and sensitivity are furnished by:

a. stage a.b. stage b.c. stage e.d. stage d.

Problem 50

In Figure 4-4, the SSB demodulation isaccomplished by:a. stages b and c.b. stages d and f.c. stages d and e.d. stages e and f.

Problem 51

In which stages of Figure 4-4 should an AGC controlsignal be applied?a. stages a and db. stages b and ec. stages c and fd. stages e and g

Problem 52

In Figure 4-5, transistor Q1 functions:

a. to recreate the original intelligence signal from the original SSB signal.

b. as a product detector.c. to mix the VFO output signal with the received RF

signal in order to produce a 453.55 kHz IF signal.d. as an RF amplifier stage of the received SSB

signal.

Problem 53

In Figure 4-5, transistor Q2 acts as:

a. an IF amplifier stage.b. a beat frequency oscillator.c. a variable frequency oscillator.d. a mixer stage.

Problem 54

In Figure 4-5, transistor Q3 acts as:

a. an IF amplifier stage.b. a beat frequency oscillator.c. a variable frequency oscillator.d. a mixer stage.

Problem 55

In Figure 4-5, transistor Q4 functions as:

a. a product detector.b. an RF mixer to create the IF frequency.c. a variable frequency oscillator.d. a beat frequency oscillator.

Problem 56

In Figure 4-5, transistor Q5 functions as:

a. a product detector.b. an RF mixer to create the IF frequency.c. a variable frequency oscillator.d. a beat frequency oscillator.

Problem 57

In Figure 4-5, the purpose of switches S1A and S1Bis to:

a. ensure that the USB or LSB mixer output signal remains in the middle of the IF bandwidth filter.

b. alter the BFO frequency slightly by selecting separate crystals.

c. alter the VFO frequency slightly by adding bias to the switching diode, D2.

d. all of the above.

Problem 58

The image shown in figure 4-6is an example of:

a. double sideband output spectrum

b. DSB-SCc. Upper sideband with a

suppressed lower sidebandd. Lower sideband with a

suppressed upper sidebande. SSB-FC