ANTENNAS
BASE STATION
The directional beam type of antenna, used within its limitations, is the most effective type to deliver the strongest signals in a
particular direction. Gain in one direction is achieved by concentrating the radiated energy into a beam much as the reflector in a
flashlight. This effect is also true when the antenna is used for receiving, resulting in a stronger signal from the direction in which the
antenna is pointed and a weaker signal from all other direct. This type of antenna is very desirable for communications with stations in
a particular area. By the addition of rotator; you will able to beam your signals in any direction.
NOTE: The reference of antenna efficiency is a standard dipole antenna. For example, a beam antenna listed as having 6 db gain
means that it has 6 db of gain over a dipole (in the direction it is pointed). Each 3 db of gain is equal to doubling the power, therefore, 6
db would equal 4 times the power. A transmitter with 3 watts output would produce as strong a signal, with 6 db gain beam, as would a
12 watt transmitter feeding a dipole.
When 360-degree coverage is needed for communicating with several stations in different directions, the ground plane type of antenna
is very effective. This type affords excellent coverage for communicating with mobile stations which are constantly moving from one
area to another.
A modification of this antenna is the colinear ground plane which is actually a form of a beam. This beaming effects of the antenna are
in a vertical direction concentrating the energy nearer the ground and reducing the sky wave which would otherwise be lost.
For a base station, the whip antenna is the least desirable type and should be used only for very short range or when no other antenna
can be installed in the space available. If it is necessary that the antenna be installed on, or adjacent to the equipment, a -V" or rabbit
ear type is much more desirable.
POLARIZATION
For the most efficient communications, the antennas at each station should be mounted in the same plane, i.e. both should be vertical
or both should be horizontal. Since a major use of Citizens Bond Radio is communicating with mobile units which are equipped with
vertically mounted whip antenna, the vertical plane is preferred.
TYPICAL AUTOMOBILE INSTALLATION
MOBILE INSTALLATION
Your
SIMBA SSB has been adjusted at the factory to
give optimum performance using a 52-ohm antenna. There are a number of
52-ohm antennas available for mobile citizens band use.
For an automobile installation, a whip may be used with good efficiency because the automobile acts as a counterpoise and reduces
detuning effects. The mounting location also has a great effect on the efficiency.
The most efficient and practical installation is a full quarter wave whip mounted on the left rear deck of fender top midway between the
rear window and bumper.
The so-called "short whip" is a less efficient antenna because the radiation area is reduced. However, full use of its capability may be
achieved since a shorter antenna may be mounted in a more advantageous position on a automobile, such as in the middle of the top.
There are also newer mobile antennas on the market which are made to replace the entertainment radio antenna and are similar in
appearance.
These antennas serve three purposes: AM and FM entertainment broadcast reception and Citizens Band transmission and reception.
For a marine installation, the full-length quarter wave whip antenna is very efficient, however, it requires radials which make it hard to
mount in small boats. Another excellent antenna is the coaxial sleeve type which requires no radial. A similar antenna is the
centerloaded 1/ 2 wave which is about the same as the full length 1/4 wave whip and it requires no radials. Care must be used when
choosing one of the shortened type antennas as considerable variation in efficiency will be found between the various makes and
models. As a general rule, avoid those with short radiating elements because the greater the radiating area, the stronger the radiated
signal will be.
Your PEARCE-SIMPSON dealer is prepared to offer advice and will help you choose the most desirable antenna for your needs.
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