Cobra Electronics 18 WX ST ユーザーズマニュアル
Mobile whip antennas utilize the metal body of the vehicle as
a ground plane. When mounted at a corner of the vehicle they
are slightly directional, in the direction of the body of the vehi-
cle. For all practical purposes, however, the radiation pattern is
non-directional. The slight directional characteristic will be
observed only at extreme distances. A standard antenna con-
nector (Type SO-239) is provided on the transceiver for easy
connection to a standard PL-259 cable termination. Cobra load-
ed-type antenna models AT-35, AT-60 and AT-70 are highly rec-
ommended for most installations. Consult your Cobra dealer
for further details (or see order form at the back of this book).
a ground plane. When mounted at a corner of the vehicle they
are slightly directional, in the direction of the body of the vehi-
cle. For all practical purposes, however, the radiation pattern is
non-directional. The slight directional characteristic will be
observed only at extreme distances. A standard antenna con-
nector (Type SO-239) is provided on the transceiver for easy
connection to a standard PL-259 cable termination. Cobra load-
ed-type antenna models AT-35, AT-60 and AT-70 are highly rec-
ommended for most installations. Consult your Cobra dealer
for further details (or see order form at the back of this book).
When installed in a boat
, the transceiver will not operate at
maximum efficiency without a ground plate unless the vessel
has a steel hull. Before installing the transceiver in a boat, con-
sult your dealer for information regarding an adequate
grounding system and prevention of electrolysis between fit-
tings in the hull and water.
has a steel hull. Before installing the transceiver in a boat, con-
sult your dealer for information regarding an adequate
grounding system and prevention of electrolysis between fit-
tings in the hull and water.
3-Way Combination Antennas are available which allow op-
eration of all three bands (AM-FM & CB), using a single
antenna. However, use of this type of antenna usually
results in less than normal transmit and receive range when
compared to a standard-type "Single Band" antenna
designed for CB only.
eration of all three bands (AM-FM & CB), using a single
antenna. However, use of this type of antenna usually
results in less than normal transmit and receive range when
compared to a standard-type "Single Band" antenna
designed for CB only.
Ignition Noise Interference
Use of a mobile receiver at low signal levels is normally limited
by the presence of electrical noise. The primary source of noise
in automobile installations is from the alternator and ignition
system in the vehicle. Under most operating conditions, when
signal level is adequate, the background noise does not present
a serious problem. Also, when extremely low level signals are
being received, the transceiver may be operated with vehicle
engine turned off. The unit requires very little current and
therefore will not significantly discharge the vehicle battery.
Even though this COBRA radio has an automatic noise limiter, in
some installations ignition interference may be high enough to
make good communications impossible. The electrical noise may
come from several sources. Many possibilities exist, and varia-
tions between vehicles require different solutions to reduce the
noise. Consult your COBRA dealer or a 2-way radio technician
for help in locating and correcting the source of severe noise.
by the presence of electrical noise. The primary source of noise
in automobile installations is from the alternator and ignition
system in the vehicle. Under most operating conditions, when
signal level is adequate, the background noise does not present
a serious problem. Also, when extremely low level signals are
being received, the transceiver may be operated with vehicle
engine turned off. The unit requires very little current and
therefore will not significantly discharge the vehicle battery.
Even though this COBRA radio has an automatic noise limiter, in
some installations ignition interference may be high enough to
make good communications impossible. The electrical noise may
come from several sources. Many possibilities exist, and varia-
tions between vehicles require different solutions to reduce the
noise. Consult your COBRA dealer or a 2-way radio technician
for help in locating and correcting the source of severe noise.
3.
Connect the antenna cable plug to the standard recep-
tacle on the unit. Most CB antennas are terminated
with a type PL-259 plug which mates with the recepta-
cle marked "ANT."
tacle on the unit. Most CB antennas are terminated
with a type PL-259 plug which mates with the recepta-
cle marked "ANT."
4.
Connect the red lead of DC power cord to +13.8 VDC.
In automobile installations, +13.8VDC is usually ob-
tained from the accessory contact in the fuse box. This
prevents the set being left on accidentally and also per-
mits operating the unit without the vehicle's engine
running.
In automobile installations, +13.8VDC is usually ob-
tained from the accessory contact in the fuse box. This
prevents the set being left on accidentally and also per-
mits operating the unit without the vehicle's engine
running.
Before installing the CB radio, visually check the ve-
hicle battery connections to determine which battery
terminal, positive or negative (positive is the larger of
the two) is grounded to the engine block (or chassis).
hicle battery connections to determine which battery
terminal, positive or negative (positive is the larger of
the two) is grounded to the engine block (or chassis).
5.
Connect the black lead to the negative side of the auto-
mobile. This is usually the chassis of the car. Any con-
venient location with good electrical contact (remove
paint) may be used.
mobile. This is usually the chassis of the car. Any con-
venient location with good electrical contact (remove
paint) may be used.
6.
Mount the microphone bracket on right side of the
transceiver or near it using two screws supplied. When
mounting in an automobile, place the bracket under
the dash so the microphone is readily accessible.
transceiver or near it using two screws supplied. When
mounting in an automobile, place the bracket under
the dash so the microphone is readily accessible.
CB Antenna
Since the maximum allowable power output to the trans-
mitter is limited by the FCC, the antenna is one important
factor affecting transmission distance. Only a properly
matched antenna system will allow maximum power trans-
fer from a 50-ohm transmission line to the radiating ele-
ment. In mobile installations (cars, trucks, boats, etc.), an
antenna system that is non-directional should be used.
mitter is limited by the FCC, the antenna is one important
factor affecting transmission distance. Only a properly
matched antenna system will allow maximum power trans-
fer from a 50-ohm transmission line to the radiating ele-
ment. In mobile installations (cars, trucks, boats, etc.), an
antenna system that is non-directional should be used.
A vertically polarized quarter-length whip antenna pro-
vides the most reliable operation and the greatest range.
The shorter loaded-type whip antennas are more attractive,
compact and adequate for applications where the maxi-
mum possible range is not required. Also the loaded whips
do not present the problems of height imposed by the full
quarter-wavelength whip.
vides the most reliable operation and the greatest range.
The shorter loaded-type whip antennas are more attractive,
compact and adequate for applications where the maxi-
mum possible range is not required. Also the loaded whips
do not present the problems of height imposed by the full
quarter-wavelength whip.
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