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Subel. ZLH
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ZLH26
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ZLH26
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Subelement ZLH
From Transmitter to Receiver
Section ZLH26
Transmission Lines
ZLH2601
Any length of transmission line may be made to appear as an infinitely long line by
A.
shorting the line at the end
B.
leaving the line open at the end
Correct Answer
C.
terminating
the line in its
characteristic
impedance
D.
increasing the standing wave ratio above unity
ZLH2601
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ZLH2602
The characteristic impedance of a transmission line is determined by the
A.
length of the line
B.
load placed on the line
Correct Answer
C.
physical
dimensions
and relative
positions
of the
conductors
D.
frequency at which the line is operated
ZLH2602
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ZLH2603
The characteristic impedance of a 20 metre length of transmission line is 52 ohm. If 10 metres is cut off, the impedance will be
A.
13 ohm
B.
26 ohm
C.
39 ohm
Correct Answer
D.
52
ohm
ZLH2603
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ZLH2604
The following feeder is the best match to the base of a quarter wave ground plane antenna
A.
300 ohm balanced feedline
Correct Answer
B.
50
ohm coaxial cable
C.
75 ohm balanced feedline
D.
300 ohm coaxial cable
ZLH2604
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ZLH2605
The designed output impedance of the antenna socket of most modern transmitters is nominally
A.
25 ohm
Correct Answer
B.
50
ohm
C.
75 ohm
D.
100 ohm
ZLH2605
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ZLH2606
To obtain efficient transfer of power from a transmitter to an antenna, it is important that there is a
A.
high load impedance
B.
low load impedance
Correct Answer
C.
correct
impedance
match
between
transmitter
and
antenna
D.
high standing wave ratio
ZLH2606
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ZLH2607
A coaxial feedline is constructed from
A.
a single conductor
B.
two parallel conductors separated by spacers
Correct Answer
C.
braid and insulation around a
central
conductor
D.
braid and insulation twisted together
ZLH2607
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ZLH2608
An RF transmission line should be matched at the transmitter end to
A.
prevent frequency drift
B.
overcome fading of the transmitted signal
C.
ensure that the radiated signal has the intended polarisation
Correct Answer
D.
transfer
maximum
power
to the
antenna
ZLH2608
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ZLH2609
A damaged antenna or feedline attached to the output of a transmitter will present an incorrect load resulting in
A.
the driver stage not delivering power to the final
B.
the output tuned circuit breaking down
Correct Answer
C.
excessive
heat
being
produced
in the
transmitter
output stage
D.
loss of modulation in the transmitted signal
ZLH2609
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ZLH2610
A result of mismatch between the power amplifier of a transmitter and the antenna is
Correct Answer
A.
reduced
antenna
radiation
B.
radiation of key clicks
C.
lower modulation percentage
D.
smaller DC current drain
ZLH2610
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ZLH2611
Losses occurring on a transmission line between a transmitter and antenna result in
Correct Answer
A.
less RF
power
being
radiated
B.
a SWR of 1:1
C.
reflections occurring in the line
D.
improved transfer of RF energy to the antenna
ZLH2611
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ZLH2612
If the characteristic impedance of a feedline does not match the antenna input impedance then
Correct Answer
A.
standing
waves
are produced in the
feedline
B.
heat is produced at the junction
C.
the SWR drops to 1:1
D.
the antenna will not radiate any signal
ZLH2612
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ZLH2613
A result of standing waves on a non-resonant transmission line is
A.
maximum transfer of energy to the antenna from the transmitter
B.
perfect impedance match between transmitter and feedline
Correct Answer
C.
reduced
transfer of RF energy to the antenna
D.
lack of radiation from the transmission line
ZLH2613
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ZLH2614
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
A.
zero
B.
5 ohm
C.
150 ohm
Correct Answer
D.
infinite
ZLH2614
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ZLH2615
A switching system to use a single antenna for a separate transmitter and receiver should also
Correct Answer
A.
disable
the
unit
not being used
B.
disconnect the antenna tuner
C.
ground the antenna on receive
D.
switch between power supplies
ZLH2615
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ZLH2616
An instrument to check whether RF power in the transmission line is transferred to the antenna is
Correct Answer
A.
a
standing
wave
ratio
meter
B.
an antenna tuner
C.
a dummy load
D.
a keying monitor
ZLH2616
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ZLH2617
This type of transmission line will exhibit the lowest loss
A.
twisted flex
B.
coaxial cable
Correct Answer
C.
open
-
wire
feeder
D.
mains cable
ZLH2617
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ZLH2618
The velocity factor of a coaxial cable with solid polythene dielectric is about
Correct Answer
A.
0.
66
B.
0.1
C.
0.8
D.
1.0
ZLH2618
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ZLH2619
This commonly available antenna feedline can be buried directly in the ground for some distance without adverse effects
A.
75 ohm twinlead
B.
300 ohm twinlead
C.
600 ohm open-wire
Correct Answer
D.
coaxial
cable
ZLH2619
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ZLH2620
If an antenna feedline must pass near grounded metal objects, the following type should be used
A.
75 ohm twinlead
B.
300 ohm twinlead
C.
600 ohm open-wire
Correct Answer
D.
coaxial
cable
ZLH2620
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