nzart-exam-generator/files/N20.TXT

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