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399 lines
7.8 KiB
Plaintext
399 lines
7.8 KiB
Plaintext
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% FILENAME = N29.TXT
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% Interference and Filtering
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% Release version 4, June 2004
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%QUESTION: 1
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#29.1 Electromagnetic compatibility is:
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two antennas facing each other
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the ability of equipment to function satisfactorily in its own environment without introducing intolerable electromagnetic disturbances
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more than one relay solenoid operating simultaneously
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the inability of equipment to function satisfactorily together and produce tolerable electromagnetic disturbances
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% ans 2
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%QUESTION: 2
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#29.2 On an amateur receiver, unwanted signals are found at every 15.625 kHz. This is probably due to:
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a low-frequency government station
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a remote radar station
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radiation from a nearby TV line oscillator
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none of these
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% ans 3
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%QUESTION: 3
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#29.3 Narrow-band interference can be caused by:
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transmitter harmonics
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a neon sign
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a shaver motor
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lightning flashes
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% ans 1
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%QUESTION: 4
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#29.4 Which of the following is most likely to cause broad-band continuous interference:
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an electric blanket switch
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a refrigerator thermostat
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a microwave transmitter
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poor commutation in an electric motor
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% ans 4
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%QUESTION: 5
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#29.5 If broadband noise interference varies when it rains, the most likely cause could be from:
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underground power cables
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outside overhead power lines
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car ignitions
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your antenna connection
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% ans 2
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%QUESTION: 6
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#29.6 Before explaining to a neighbour that the reported interference is due to a lack of immunity in the neighbour's electronic equipment:
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disconnect all your equipment from their power sources
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write a letter to the MED
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make sure that there is no interference on your own domestic equipment
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ignore all complaints and take no action
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% ans 3
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%QUESTION: 7
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#29.7 A neighbour's stereo system is suffering RF break-through. One possible cure is to:
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put a ferrite bead on the transmitter output lead
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put a capacitor across the transmitter output
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use open-wire feeders to the antenna
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use screened wire for the loudspeaker leads
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% ans 4
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%QUESTION: 8
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#29.8 When living in a densely-populated area, it is wise to:
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always use maximum transmitter output power
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use the minimum transmitter output power necessary
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only transmit during popular television programme times
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point the beam at the maximum number of television antennas
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% ans 2
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%QUESTION: 9
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#29.9 When someone in the neighbourhood complains of TVI it is wise to:
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deny all responsibility
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immediately blame the other equipment
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inform all the other neighbours
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check your log to see if it coincides with your transmissions
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% ans 4
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%QUESTION: 10
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#29.10 Cross-modulation is usually caused by:
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rectification of strong signals in overloaded stages
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key-clicks generated at the transmitter
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improper filtering in the transmitter
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lack of receiver sensitivity and selectivity
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% ans 1
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%QUESTION: 11
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#29.11 When the signal from a transmitter overloads the audio stages of a broadcast receiver, the transmitted signal:
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can be heard irrespective of where the receiver is tuned
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appears only when a broadcast station is received
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is distorted on voice peaks
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appears on only one frequency
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% ans 1
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%QUESTION: 12
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#29.12 Cross-modulation of a broadcast receiver by a nearby transmitter would be noticed in the receiver as:
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a lack of signals being received
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the undesired signal in the background of the desired signal
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interference only when a broadcast signal is received
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distortion on transmitted voice peaks
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% ans 2
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%QUESTION: 13
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#29.13 Unwanted signals from a radio transmitter which cause harmful interference to other users are known as:
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rectified signals
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re-radiation signals
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reflected signals
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harmonic and other spurious signals
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% ans 4
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%QUESTION: 14
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#29.14 To reduce harmonic output from a transmitter, the following could be put in the transmission line as close to the
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transmitter as possible:
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wave trap
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low-pass filter
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high-pass filter
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band reject filter
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% ans 2
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%QUESTION: 15
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#29.15 To reduce energy from an HF transmitter getting into a television receiver, the following could be placed in the TV antenna lead as close to the TV as possible:
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active filter
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low-pass filter
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high-pass filter
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band reject filter
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% ans 3
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%QUESTION: 16
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#29.16 A low-pass filter used to eliminate the radiation of unwanted signals is connected to the:
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output of the balanced modulator
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output of the amateur transmitter
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input of the stereo system
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input of the mixer stage of your SSB transmitter
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% ans 2
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%QUESTION: 17
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#29.17 A band-pass filter will:
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pass frequencies each side of a band
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attenuate low frequencies but not high frequencies
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attenuate frequencies each side of a band
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attenuate high frequencies but not low frequencies
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% ans 3
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%QUESTION: 18
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#29.18 A band-stop filter will:
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pass frequencies each side of a band
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stop frequencies each side of a band
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only allow one spot frequency through
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pass frequencies below 100 MHz
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% ans 1
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%QUESTION: 19
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#29.19 A low-pass filter for a high frequency transmitter output would:
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attenuate frequencies above 30 MHz
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pass audio frequencies below 3 kHz
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attenuate frequencies below 30 MHz
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pass audio frequencies above 3 kHz
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% ans 1
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%QUESTION: 20
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#29.20 Installing a low-pass filter between the transmitter and transmission line will:
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permit higher frequency signals to pass to the antenna
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ensure an SWR not exceeding 2:1
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reduce the power output back to the legal maximum
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permit lower frequency signals to pass to the antenna
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% ans 4
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%QUESTION: 21
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#29.21 A low-pass filter may be used in an amateur radio installation:
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to attenuate signals lower in frequency than the transmission
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to attenuate signals higher in frequency than the transmission
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to boost the output power of the lower frequency transmissions
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to boost the power of higher frequency transmissions
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% ans 2
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%QUESTION: 22
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#29.22 Television interference caused by harmonics radiated from an amateur transmitter could be eliminated by fitting:
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a low-pass filter in the TV receiver antenna input
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a high-pass filter in the transmitter output
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a low-pass filter in the transmitter output
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a band-pass filter to the speech amplifier
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% ans 3
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%QUESTION: 23
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#29.23 A high-pass filter can be used to:
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prevent interference to a telephone
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prevent overmodulation in a transmitter
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prevent interference to a TV receiver
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pass a band of speech frequencies in a modulator
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% ans 3
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%QUESTION: 24
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#29.24 A high-pass RF filter would normally be fitted:
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between transmitter output and feedline
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at the antenna terminals of a TV receiver
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at the Morse key or keying relay in a transmitter
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between microphone and speech amplifier
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% ans 2
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%QUESTION: 25
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#29.25 A high-pass filter attenuates:
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a band of frequencies in the VHF region
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all except a band of VHF frequencies
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high frequencies but not low frequencies
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low frequencies but not high frequencies
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% ans 4
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%QUESTION: 26
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#29.26 An operational amplifier connected as a filter always utilises:
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positive feedback to reduce oscillation
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negative feedback
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random feedback
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inductors and resistor circuits only
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% ans 2
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%QUESTION: 27
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#29.27 The voltage gain of an operational amplifier at low frequencies is:
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very high but purposely reduced using circuit components
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very low but purposely increased using circuit components
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less than one
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undefined
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% ans 1
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%QUESTION: 28
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#29.28 The input impedance of an operational amplifier is generally:
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very high
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very low
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capacitive
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inductive
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% ans 1
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%QUESTION: 29
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#29.29 An active audio low-pass filter could be constructed using:
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zener diodes and resistors
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electrolytic capacitors and resistors
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an operational amplifier, resistors and capacitors
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a transformer and capacitors
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% ans 3
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%QUESTION: 30
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#29.30 A filter used to attenuate a very narrow band of frequencies centred on 3.6 MHz would be called:
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a band-pass filter
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a high-pass filter
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a low-pass filter
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a notch filter
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% ans 4
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