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INSTALLATION
A
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 installation is from the generator 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 vehicles engine turned off. The unit
requires very little current and therefore will not significantly discharge the vehicle battery.
Even though the transceiver has ANL and NB controls, in some installation ignition
interference may be high enough to make good communications impossible. The electrical
noise may come from several sources. Many possibilities exist, as variations between vehicles
require different solutions to reduce the noise.
ANTENNA
A vertically polarized, quarter-wavelength whip antenna provides the most reliable operation
and greatest range. Shorter, loaded-type whip antennas are more attractive, compact and
adequate for applications where the maximum possible distance is not required. Also, loaded
whips do not present the problems of high wind resistant 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 purpose, 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.
If the transceiver is not mounted on a metal surface, it is necessary to run a separate ground
wire from the unit to good metal electrical ground in the vehicle. 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.
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INSTALLATION
A
TUNING THE ANTENNA FOR OPTIMUM S.W.R
Since there is such a wide variety of a base and mobile antenna, this section will strictly
concern itself to the various types of mobile adjustable antennas.
Because the antenna length is directly related to the channel frequency, it must be tuned to
resonate optimally on all channels of the transceiver. Channel 1 requires a longer antenna than
Channel 40 because it is lower in its frequency of operation.
Due to the various methods of adjusting antennas for proper S.W.R. we have chosen what
we think is the optimum method:
A. Antenna with adjustment screws (set screws).
1. Starts with the antenna extended and tighten the set screw lightly enough so that the
antenna can be lightly tapped with your finger for easy adjustment.
2. Set your transceiver to Channel 20. Press the PTT (push-to-talk) switch, and tap the
antenna (making it shorter). The S.W.R meter will show a lower reading each time the
antenna is tapped. By continuing to shorten the antenna, you will notice the S.W.R reading
will reach a low point and then start rising again. This means that you have passed the
optimum point for Channel 20.
Extend the antenna a short distance and again follow the procedure above. When the lowest
point has been reached, switch to Channel 1 and then to Channel 40 and compare S.W.R
readings. They should be almost equal.
NOTE
The proper setting is achieved when the SWR is 1.5 or
below, and when it has the same reading for channels 1
and 40.
B. Antennas which must be cut to proper length
1. Follow the same procedure as above but adjust the length by cutting in 1/8” increments
until a good match is obtained.
2. Be very careful not to cut too much at one time, as one it is cut, it can no longer be
lengthen.
3. The whip is easily cut by filing a notch all the way around and breaking the piece off with
pliers.
