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INSTALLATION
IGNITION NOISE INTERFERENCE
Use of a molafle receiver at tow 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. In addition, 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 vehicles battery.
In some installation. ignition Interference may be high enough to make good communications
Impossible. The electrical noise may canoe tram several sources. Many possibilities exist, as
variations between vehicles require different solutions to redact 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
advocate for applications where the maximum possible distance Is not required. In addition,
loaded whips do not present the problems of high wind resistant imposed by a full quarter-
wavelength whip.
Mobile wtdp antennas uttlite 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 non-directional. The slight directional
characteristic will be observed only at extreme distances. A standard antenna connector (type
50.239) Is provided on the transceiver far easy connection to a standard PL-259 cable
termination.
If the transceiver is not mourned 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 dealef for information regarding an
adequate grounding system and prevention of electrolysis between fittings in the hull and water.
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INSTALLATION
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 itseti to the various types of mobile adjustable antennas.
Because the antenna length is directly related to the channel frequency, It oust be tuned to
resonate optimally on all channels of the transceiver. Channel 1 requires a longer antenna than
Channel 40 because t 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 setscrew lightly trough so that the
antenna can be lightly tapped with your finger for easy adjustment.
Set your transceiver to Channel 20. Press the P11' (push-to-talk) switch, and tap the
antenna (making It Shorter). The S.W.R meter will show a lower reading each time time
antenna Is lapped. 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 I and then to Channel 40 and compare S.WR
readings. They should be almost equal,
NOTE
The proper selling is achieved when the SWR is
1.5
or
I
below, and when it has
similar reading For
channels I and
40.
B. Antennas which must be cut to proper length
1. F011ow the same procedure as above but adjust the length by cutting In 1/9" Increments
until a good match Is obtained.
2. Be very careful not to corE
100
much at one time, as once It Is cut, It can no longer be
lengthened.
3. The whip Is easily cut by filing a notch all the way around and breaking the piece elf with
pliers,
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