ANTENNA SYSTEM
A mobile antenna system is not limited to the antenna only. The transmission line as well as the
vehicle are important factors in the total antenna system. Therefore, you must use the correct type
of transmission line and mount the antenna securely in a position that will give you optimal results.
Use coaxial cable with an impedance of 50 Ohms. We suggest type RG 58/U for lengths under 2.5
m or RG 8/U for longer lengths. Generally speaking, you should keep the length of the transmission
line to a minimum.
The above discussion is as important for reception as it is for the transmission. If a mismatch
exists between the antenna and the receiver, the excellent sensivity and signal-to-noise radio of
the receiver circuit will be defeated.
MOBILE ANTENNAS
A few general rules should help you to install any mobile antenna properly.
• Keep it as far as possible from the main bulk of the vehicle.
• During operation, it must be vertical, and rigid enough to remain vertical when the vehicle or boat
is in motion.
• Mount it as far as possible from sources of noise (ignition system, gauges, etc.) and keep the
transmission line away from these noise sources.
• An antenna mounted in a boat requires a good ground connection. This can be either a metal
hull or a ground made of tin-foil or copper sheeting. This ground should cover an area of at least
1 m
2
or more. Be sure the transceiver also has an adequate ground.
There are many types of mobile CB antennas: a full quarter-wave length whip, a centerloaded
whip, top loaded whip and the base loaded type.
A vertically polarized whip antenna is best suited for mobile service. It is omni-directional.
If it’s the loaded type, you will nd it a phisically shorter antenna. But, for greater efciency the
2.5 m long, full quarter-wave whip is better. Antenna length is directly related to efciency.
Generally, the longer it is the more efcient.
