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Ignition Noise InterferenceAntennas
Use of a mobile receiver at low signal levels is
normally limited by the presence of electrical
noise.The primary source of noise in automobiles
is from the alternator and ignition system.
Typically,when signal level is adequate,the back-
ground noise does not present a serious problem.
Also,when extremely low level signals are being
received,the transceiver may be operated with
the vehicle’s engine turned off.The unit requires
very little current and therefore will not signifi-
cantly discharge the vehicle’s battery.
Even though the Cobra 25 NW ST has an auto-
matic noise limiter,in some installations ignition
interference may be high enough to make good
communications impossible. Many possibilities
exist and variations between vehicles require
different solutions.Consult your COBRA dealer or
a 2-way radio technician for help in locating the
source of a severe noise.
CB Antenna
Since the maximum allowable power output of
the transmitter is limited by the FCC,the antenna
is critical in affecting transmission distance.Only
a properly matched antenna system will allow
maximum power output.Cobra loaded type
antenna models are highly recommended for
most installations.Consult your Cobra dealer for
further details, or call 773.889.3087 and speak to
a Cobra representative.
Marine Installation
The transceiver will not operate at maximum effi-
ciency in a boat without a ground plate,(unless it
has a steel hull). Before attempting installation ,
consult your dealer for information regarding an
adequate grounding system and prevention of
electrolysis between fittings in the hull and water.
CB Antenna
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Note
For optimum performance in
passenger cars the ideal anten-
na location is on the center of
the roof. Second choice is on the
center of the trunk.
Note
Because many newer trucks
feature fiberglass door skins,the
outside mirror must be ground-
ed to the chassis via a ground
strap,if the antenna is mounted
on the mirror bracket.
Note
3-way Combination Antennas
are also available which allow
operation of all three bands
(AM-FM & CB),using a single
antenna.However,this type of
antenna usually results in less
than normal transmit and
receive range when compared
to a standard-type“Single
Band”CB antenna.Call
773.889.3087 for further infor-
mation.
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1
A standard antenna connector is provided
on the transceiver for easy connection.
25 NWST Manual3.3 6/15/99 12:43 PM Page 6