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 installations 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 vehicle engine turned off. The unit requires very little current and therefore
will not significantly discharge the vehicle battery.
Even though the SS —7000 DX has ANL and NB controls, in some installations
ignition interference may be high enough to make good communications impossible.
The electrical noise may come from several sources. Many possibilities exist and
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, the loaded whips do not present the problems of height 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 a 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.
