Cobra Electronics 19 DX II manual InstallationCont, CB Antenna, Ignition Noise Interference

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 non-directional should be used.

A vertically polarized, quarter-wavelength whip antenna provides the most reliable operation and greatest range. The shorter, loaded-type whip antennas are more attractive, compact and adequate for applications where the maximum possible distance is not required. Also, the loaded whips do not present the problems of height imposed by a full quarter-wavelength whip.

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 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 SO-239) is provided on the transceiver for easy connection to a standard PL 259 cable termination. Cobra loaded-type antenna models ATW-500, AT-55, ATW-1000 and ATW-400 are highly recommended for most installations. Consult your Cobra dealer for further details.

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, consult your dealer for information regarding an adequate grounding system and prevention of electrolysis between fittings in the hull and water.

3-Way Combinations Antennas are available which allow operation 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.

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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 an therefore will not significantly discharge the vehicle battery.

Even though the COBRA radio has an automatic noise limiter, in some installations, ignition interference and other forms of automobile generated noise may be high enough to make good communications difficult. The electrical noise may come from several sources. Many possibilities exist and variations 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.

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 12VDC power pack that has been specially designed for the purpose. It is available as optional equipment from your COBRA dealer. It consists of a 120-volt, 60 Hz AC to 12-volt DC power converter with a 3A rating. Simply connect the red (+) and black (-) leads of the transceiver to the corresponding terminals of the power packs.

DO NOT ATTEMPT TO OPERATE THIS TRANSCEIVER BY CONNECTING DIRECTLY TO 120 VAC. SERIOUS DAMAGE WILL RESULT.

Temporary Mobile Operations

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 transceiver for temporary use.

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