# Chapter 4 Problems ECET 214 Prof. Park NJIT.

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Chapter 4 Problems ECET 214 Prof. Park NJIT

Problem 1 SSB transmitters are usually rated in terms of: a. power gain b. voltage gain c. modulation index d. peak envelope power

Problem 2 Which of the following is required for SSB transmission? a. carrier elimination b. elimination of one sideband c. a and b d. none of the above

Problem 3 Which of the following is NOT an advantage that the phase method of generating has over the filter method? 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 of SSB generation is: a. requires two balance modulators b. does not use high Q filters c. 90° phase-shifting network for intelligence signal d. all of the above

Problem 5 Which of the following can be used as an SSB demodulator? a. RF amplifier b. audio amplifier c. AGC circuitry d. mixer

Problem 6 At 100% modulation, an AM signal has a total power of 1200 watts. If it was converted to SSB and the sideband component had the same amplitude as before, the total power would be: a. 100 watts b. 200 watts c. 400 watts d. 800 watts

Problem 7 The PEP rating of an SSB transmitter is often misleading due 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 are completely eliminated, the resulting signal is referred to as: a. SSB. b. SSBSC. c. ACSSB. d. vestigial sideband.

Problem 9 If the carrier is reduced in amplitude and one of the sidebands is completely eliminated, the resulting signal is referred to as: a. independent sideband. b. SSBSC c. ACSSB. d. vestigial sideband.

Problem 10 The type of sideband that involves having the upper sideband contain different information than the lower sideband is referred to as: a. independent sideband. b. SSBSC c. ACSSB. d. vestigial sideband.

Problem 11 The type of sideband that is used for television video transmission is called: a. independent sideband b. SSBSC c. ACSSB d. vestigial sideband

Problem 12 A more recently developed system of sideband that involves compressing the amplitude of the intelligence signal before modulation occurs is called: 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 SSB transmitter being modulated with a voice intelligence 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 a balanced modulator? a. a dual-gate FET and a band-pass filter b. a push-pull modulator c. a ring-diode modulator d. an LM1496 integrated circuit stage

Problem 17 In a push-pull modulator, the carrier suppression is 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 modulator such as the LM1496, carrier suppression is accomplished 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 frequency range 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 using audio frequencies ranging from 100 Hz to 3 kHz, the upper and lower sidebands generated by the balanced modulator are separated by: a. 500 Hz. b. 200 Hz. c. 6 kHz. d. 40 Hz.

Problem 21 Calculate the required Q for the bandpass filter depicted in Figure 4-1 for 80 dB sideband suppression if the carrier frequency component of the IF is 455 kHz. a b. 56,875 c. 227,500 d. 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 over crystal 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 for a 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 the bandpass frequencies of a ceramic filter is called: 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 SSB transmitters 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, bias magnets 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 Q required in the linear amplifier is approximately: a. 20. b. 10. c. 15. d. 100.

Problem 29 In Figure 4-2, the output signal of 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 signal of 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 31 In Figure 4-2, the first mixer and 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 32 In Figure 4-2, the second mixer and 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 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 and Q2 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 or LSB 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 in transmitter design? a. filter method b. lattice method c. amplitude-compandoring method d. phase method

Problem 38 Which is the most popular method used to generate SSB in transmitter design? a. filter method b. lattice method c. amplitude-compandoring method d. phase method

Problem 39 The main disadvantage of the phase method in generating SSB 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 dBm power levels and at the same time decreases all positive 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 negative dBm power levels and at the same time increases 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 of the 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 f b. stages d and e c. stages b and e d. stages a and c

Problem 48 In Figure 4-4, what frequency must the BFO be set at for optimum results? a. 455 kHz b. 20 MHz c. 1 MHz d. 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 is accomplished 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 control signal be applied? a. stages a and d b. stages b and e c. stages c and f d. 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 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 S1B is 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 4-6 is an example of: a. double sideband output spectrum b. DSB-SC c. Upper sideband with a suppressed lower sideband d. Lower sideband with a suppressed upper sideband e. SSB-FC