Ignition System - Realistic TRC-411 Owner's Manual

NOISE
In Mobile operation, your vehicle or boat can be the cause of much noise
interference. Since the receiver section of your transceiver is very
sensitive, it will pick up even the smallest noise signals and amplify them.
Any noise that you hear in the transceiver is almost totally from external
sources. The receiver itself is exceptionally quiet.
If the noise is
continuous and fairly loud, it cannot be totally eliminated by the Auto-
matic Noise Limiter circuit. You must solve the problem at its source.
To find out if the noise is from your ignition system, try this simple test.
Turn off your ignition switch and set it to ACC (accessories). This turns
off the ignition, but supplies power to the Transceiver, Most of the noise
will probably disappear, indicating that the source of noise is your
vehicle's ignition or other electrical systems.
IGNITION SYSTEM
Ignition-type noise can be identified by the fact that it varies with the
speed of the engine. It consists of a series of popping sounds. There are
a number of things that can be done to reduce this type of noise.
1. Use only the "radio suppression type" high-voltage ignition wire. Most
new cars come already equipped with this type of wire.
2. Inspect the high voltage ignition wire and all connections made with
this wire. Old ignition wire may develop leakage, resulting in hash.
3. If noise persists, replace the spark plugs with the spark plugs that have
suppressor resistors built-in. Be sure to use the correct type for your
vehicle.
Other sources of noise are: generator/alternator, regulator, gauges and
static discharge. Most of these types of noise can be efficiently reduced
or eliminated by using bypass capacitors at the various output voltage
points. We suggest you check your Radio Shack-store for a selection of
noise reduction accessories.
EXCESSIVE NOISE INTERFERENCE
Position antenna as far away from CB as possible.
The hissing or static received with RECEIVING RANGE control in
DISTANT position is normal.
Atmospheric conditions sometimes cause signals to "skip," resulting in
unwanted interference from distant CB transmissions.
Garbled "Donald Duck" type voice may indicate SSB (single side band)
transmission on your channel. Select an alternate clear channel.
(Common SSB channels are channel 16 and 36 through 40.)