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Installation (Cont.)
CB Antenna
Since the maximum allowable power output of the transmitter is limited by the FCC, the antenna is one important factor affecting transmission distance. Only a properly matched antenna system will allow maximum power transfer from the 50 ohm transmission line to the radiating element. In mobile installations (cars, trucks, boats, etc.), an antenna system that is
A vertically polarized,
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 direc- tion of the body of the vehicle. For all practical purposes, however, the radiation pattern is nondirectional. The slight directional characteristic will be observed only at extreme distances. A standard antenna connector (type
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 trans- ceiver in a boat, consult your dealer for information regarding an adequate ground- ing system and prevention of electrolysis between fittings in the hull and water.
Installation (Cont.)
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 the COBRA 25 LTD ST has an automatic noise limiter, in some instal- lations ignition interference may be high enough to make good communications impossible. The electrical noise may come from several sources. Many possibili- ties exist and variations between vehicles require different solutions to reduce the noise. Consult your COBRA dealer or a
Base Station Operation (Operation from 120VAC, House Current)
To operate your transceiver from your home or office, using the regular house current as the power source, you will require a 12 VDC power pack that has been specially designed for the purpose. It is available as optional equipment from your COBRA dealer. It consists of a
DO NOT ATTEMPT TO OPERATE THIS TRANSCEIVER BY CONNECTING DIRECTLY TO 120 VAC.
Temporary Mobile Operation
To operate your COBRA transceiver from a car on a temporary basis, you may want to purchase an optional cigar lighter adapter from your COBRA dealer. This adapter and a magnetic mount antenna allow you to quickly "install" your trans- ceiver for temporary use.
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