MIDLAND Alan 199-A - Manual (Page 21)

6 | Alan 199 Instruction Guide
ANTENNA SYSTEM
A mobile antenna system is not limited to just the antenna. The transmis-
sion line as well as the vehicle are important factors in the total anten-
na 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. Ge-
nerally speaking, you should keep the length of the transmission line to
a minimum. The above discussion is as important for reception as for the
transmission. If a mismatch exists between the antenna and the receiver,
the excellent sensitivity and signal-to-noise radio of the receiver circuit
will be defeated.
Suggestions
A few general rules should help you to install any mobile antenna pro-
perly.
• Keep it as far as possible from the main bulk of the vehicle.
• During operation, it must be vertical, and rigid enough to remain ver-
tical 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 m2 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 are typical. A vertically polarized
whip antenna is best suited for mobile service. It is omnidirectional. If it’s
the loaded type, you will find it a physically shorter antenna. But, for gre-
ater efficiency the 2.5 m long, full quarter-wave whip is better. Antenna
length is directly related to efficiency.
Generally, the longer it is, the more efficient will be.
There are many possible antenna locations on a car.
Four of the most popular are shown and discussed on the following.
Roof Mount
In this position the antenna radiates equally in all directions. Since the