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266 lines
4.5 KiB
Plaintext
266 lines
4.5 KiB
Plaintext
% FILENAME = N20.TXT
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% Harmonics and Parasitics
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% Release version 2, January 00
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%QUESTION: 1
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#20.1 A harmonic of a signal transmitted at 3525 kHz would be expected to occur at:
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3573 kHz
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7050 kHz
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14025 kHz
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21050 kHz
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% ans 2
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%QUESTION: 2
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#20.2 The third harmonic of 7 MHz is:
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10 MHz
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14 MHz
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21 MHz
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28 MHz
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% ans 3
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%QUESTION: 3
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#20.3 The fifth harmonic of 7 MHz is:
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12 MHz
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19 MHz
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28 MHz
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35 MHz
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% ans 4
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%QUESTION: 4
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#20.4 Excessive harmonic output may be produced in a transmitter by:
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a linear amplifier
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a low SWR
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resonant circuits
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overdriven amplifier stages
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% ans 4
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%QUESTION: 5
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#20.5 Harmonics may be produced in the RF power amplifier of a transmitter if:
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the modulation level is too low
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the modulation level is too high
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the oscillator frequency is unstable
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modulation is applied to more than one stage
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% ans 2
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%QUESTION: 6
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#20.6 Harmonics produced in an early stage of a transmitter may be reduced in a later stage by:
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increasing the signal input to the final stage
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using FET power amplifiers
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using tuned circuit coupling between stages
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using larger value coupling capacitors
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% ans 3
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%QUESTION: 7
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#20.7 Harmonics are produced when:
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a resonant circuit is detuned
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negative feedback is applied to an amplifier
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a transistor is biased for class A operation
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a sine wave is distorted
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% ans 4
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%QUESTION: 8
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#20.8 Harmonic frequencies are:
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always lower in frequency than the fundamental frequency
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at multiples of the fundamental frequency
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any unwanted frequency above the fundamental frequency
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any frequency causing TVI
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% ans 2
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%QUESTION: 9
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#20.9 An interfering signal from a transmitter has a frequency of 57 MHz. This signal could be the:
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seventh harmonic of an 80 meter transmission
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third harmonic of a 15 metre transmission
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second harmonic of a 10 metre transmission
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crystal oscillator operating on its fundamental
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% ans 3
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%QUESTION: 10
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#20.10 To minimise the radiation of one particular harmonic, one can use a:
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wave trap in the transmitter output
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resistor
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high pass filter in the transmitter output
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filter in the receiver lead
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% ans 1
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%QUESTION: 11
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#20.11 A low-pass filter is used in the antenna lead from a transmitter:
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to reduce key clicks developed in a CW transmitter
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to increase harmonic radiation
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to eliminate chirp in CW transmissions
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to reduce radiation of harmonics
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% ans 4
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%QUESTION: 12
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#20.12 The following is installed in the transmission line as close as possible to a HF transmitter to reduce harmonic output:
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a middle-pass filter
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a low-pass filter
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a high-pass filter
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a band-reject filter
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% ans 2
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%QUESTION: 13
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#20.13 A low pass filter will:
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suppress sub-harmonics
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reduce harmonics
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always eliminate interference
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improve harmonic radiation
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% ans 2
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%QUESTION: 14
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#20.14 A spurious transmission from a transmitter is:
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an unwanted emission unrelated to the output signal frequency
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an unwanted emission that is harmonically related to the modulating audio frequency
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generated at 50 Hz
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the main part of the modulated carrier
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% ans 1
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%QUESTION: 15
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#20.15 A parasitic oscillation:
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is an unwanted signal developed in a transmitter
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is generated by parasitic elements of a Yagi beam
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does not cause any radio interference
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is produced in a transmitter oscillator stage
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% ans 1
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%QUESTION: 16
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#20.16 Parasitic oscillations in a RF power amplifier can be suppressed by:
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pulsing the supply voltage
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placing suitable chokes, ferrite beads or resistors within the amplifier
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screening all input leads
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using split-stator tuning capacitors
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% ans 2
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%QUESTION: 17
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#20.17 Parasitic oscillations in the RF power amplifier stage of a transmitter may occur:
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at low frequencies only
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on harmonic frequencies
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at high frequencies only
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at high or low frequencies
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% ans 4
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%QUESTION: 18
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#20.18 Transmitter power amplifiers can generate parasitic oscillations on:
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the transmitter's output frequency
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harmonics of the transmitter's output frequency
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frequencies unrelated to the transmitter's output frequency
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VHF frequencies only
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% ans 3
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%QUESTION: 19
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#20.19 Parasitic oscillations tend to occur in:
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high voltage rectifiers
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high gain amplifier stages
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antenna matching circuits
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SWR bridges
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% ans 2
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%QUESTION: 20
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#20.20 Parasitic oscillations can cause interference. They are:
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always the same frequency as the mains supply
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always twice the operating frequency
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not related to the operating frequency
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three times the operating frequency
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% ans 3
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