nzart-exam-generator/files/N26.TXT
2016-12-30 23:01:50 +13:00

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