Dodge Stealth 1994, Service Manual

Page: 379 / 434

CHASSIS ELECTRICAL
Radio and Tape Player
A - Z
Noise appears at certain places when traveling (FM).
Do the following measures eliminate the noise?
l
Change to a different station with a strong signal to
boost resistance to interference.
l
Suppress high tones to reduce noise.
l
Extend antenna completely. (Whip antenna)
Yes
OK
No
If there is more noise than other radios, find out the noise conditions and
the name and frequency of the receiving stations from the user,
and consult with the service center.
NOTE
About FM waves:
FM waves have the same properties as light, and
can be deflected and blocked. Wave reception is not
possible in the shadow of obstructions such as
buildings or mountains.
The signal becomes weak as the distance from
the station’s transmission antenna increases.
Although this may vary according to the signal
strength of the transmitting station and interven-
ing geographical formations or buildings, the
area of good reception is approx. 20 25 km (12
16 miles) for stereo reception, and 30 40 km
(19 25 miles) for monaural reception.
2. The signal becomes weak when an area of
shadow from the transmitting antenna (places
where there are obstructions such as mountains
or buildings between the antenna and the car),
FM Broadcast Good Reception Areas
and noise will appear. <This is called first fading,
and gives a steady buzzing noise.>
3. If a direct signal hits the antenna at the same
time as a signal reflected by obstructions such
as mountains or buildings, interference of the
two signals will generate
traveling,
noise will appear each time the vehicle’s anten-
na passes through this kind of obstructed area.
The strength and interval of the noise -varies
according to the signal strength and the condi-
tions of deflection. <This is called multipath
noise, and is a repetitious buzzing.>
4.
Since FM stereo transmission and reception has
a weaker field than monaural, it is often accom-
panied by a hissing noise.
FM Signal Characteristics and Signal Interference