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280 lines
4.7 KiB
Plaintext
280 lines
4.7 KiB
Plaintext
% FILENAME = N26.TXT
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% Transmission Lines
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% Release version 2, January 2000
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%Question: 1
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#26.1 Any length of transmission line may be made to appear as an infinitely
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long line by:
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shorting the line at the end
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leaving the line open at the end
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terminating the line in its characteristic impedance
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increasing the standing wave ratio above unity
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% ans 3
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%Question: 2
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#26.2 The characteristic impedance of a transmission line is determined by the:
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length of the line
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load placed on the line
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physical dimensions and relative positions of the conductors
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frequency at which the line is operated
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% ans 3
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%Question: 3
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#26.3 The characteristic impedance of a 20 metre length of transmission line is
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52 ohm. If 10 metres is cut off, the impedance will be:
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13 ohm
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26 ohm
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39 ohm
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52 ohm
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% ans 4
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%Question: 4
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#26.4 The following feeder is the best match to the base of a quarter wave
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ground plane antenna:
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300 ohm balanced feedline
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50 ohm coaxial cable
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75 ohm balanced feedline
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300 ohm coaxial cable
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% ans 2
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%Question: 5
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#26.5 The designed output impedance of the antenna socket of most modern
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transmitters is nominally:
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25 ohm
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50 ohm
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75 ohm
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100 ohm
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% ans 2
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%Question: 6
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#26.6 To obtain efficient transfer of power from a transmitter to an antenna,
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it is important that there is a:
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high load impedance
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low load impedance
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correct impedance match between transmitter and antenna
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high standing wave ratio
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% ans 3
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%Question: 7
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#26.7 A coaxial feedline is constructed from:
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a single conductor
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two parallel conductors separated by spacers
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braid and insulation around a central conductor
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braid and insulation twisted together
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% ans 3
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%Question: 8
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#26.8 An RF transmission line should be matched at the transmitter end to:
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prevent frequency drift
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overcome fading of the transmitted signal
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ensure that the radiated signal has the intended polarisation
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transfer maximum power to the antenna
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% ans 4
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%Question: 9
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#26.9 A damaged antenna or feedline attached to the output of a transmitter
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will present an incorrect load resulting in:
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the driver stage not delivering power to the final
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the output tuned circuit breaking down
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excessive heat being produced in the transmitter output stage
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loss of modulation in the transmitted signal
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% ans 3
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%Question: 10
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#26.10 A result of mismatch between the power amplifier of a transmitter and
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the antenna is:
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reduced antenna radiation
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radiation of key clicks
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lower modulation percentage
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smaller DC current drain
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% ans 1
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%Question: 11
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#26.11 Losses occurring on a transmission line between a transmitter and
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antenna result in:
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less RF power being radiated
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a SWR of 1:1
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reflections occurring in the line
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improved transfer of RF energy to the antenna
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% ans 1
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%Question: 12
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#26.12 If the characteristic impedance of a feedline does not match the antenna
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input impedance then:
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standing waves are produced in the feedline
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heat is produced at the junction
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the SWR drops to 1:1
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the antenna will not radiate any signal
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% ans 1
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%Question: 13
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#26.13 A result of standing waves on a non-resonant transmission line is:
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maximum transfer of energy to the antenna from the transmitter
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perfect impedance match between transmitter and feedline
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reduced transfer of RF energy to the antenna
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lack of radiation from the transmission line
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% ans 3
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%Question: 14
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#26.14 A quarter-wave length of 50-ohm coaxial line is shorted at one end. The
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impedance seen at the other end of the line is:
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zero
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5 ohm
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150 ohm
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infinite
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% ans 4
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%Question: 15
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#26.15 A switching system to use a single antenna for a separate transmitter
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and receiver should also:
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disable the unit not being used
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disconnect the antenna tuner
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ground the antenna on receive
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switch between power supplies
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% ans 1
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%Question: 16
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#26.16 An instrument to check whether RF power in the transmission line is
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transferred to the antenna is:
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a standing wave ratio meter
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an antenna tuner
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a dummy load
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a keying monitor
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% ans 1
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%Question: 17
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#26.17 This type of transmission line will exhibit the lowest loss:
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twisted flex
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coaxial cable
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open-wire feeder
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mains cable
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% ans 3
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%Question: 18
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#26.18 The velocity factor of a coaxial cable with solid polythene dielectric
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is about:
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0.66
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0.1
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0.8
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1.0
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% ans 1
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%Question: 19
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#26.19 This commonly available antenna feedline can be buried directly in the
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ground for some distance without adverse effects:
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75 ohm twinlead
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300 ohm twinlead
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600 ohm open-wire
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coaxial cable
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% ans 4
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%Question: 20
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#26.20 If an antenna feedline must pass near grounded metal objects, the
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following type should be used:
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75 ohm twinlead
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300 ohm twinlead
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600 ohm open-wire
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coaxial cable
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% ans 4
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