RADIO INTERFERENCE
In the event that your player suffers from interference from your vehicles ignition or
charging system, please read carefully the guidance given below. It should be noted that
in the majority of cases, interference is mostly caused by a missing or defective device
or the ignition HT leads are worn or are of poor quality.
The ignition circuit consists of the coil, distributor, spark plug leads, and spark plugs, all
of these components pass very high voltage and unless they are screened or suppressed
will cause electrical interference to the radio. This can occur in any of the following ways:
a. Travel along the +12 Volt supply cable to the radio or
b. As a radio frequency which is received by the car aerial and processed as a signal or
c. By both points a and b shown above.
Before replacing or adding any suppression devices or filters, check carefully that the car
aerial and screened lead are not damaged and that the radio cassette player is properly
earthed and tuned to the correct frequency. As radio interference can be caused by many
factors, locating the exact cause of the problem can often be very difficult, and trouble
shooting is usually best left to a professional car radio installer, or to the main agent of
your vehicle.
If you decide to try and cure the problem yourself, the large array of suppression kits/devices
currently available from high street motor factors or your vehicles main agent may be
confusing you. Each type of device is designed to filter out electrical interference at
specific frequencies it is unfortunately trial and error, if one device works and another
does not, therefore you may have to try several different types of filters before you have
any success. Instructions on fitting the filters etc. are usually supplied with the kits.
Another source of interference is the alternator or dynamo, this can cause a whining noise
relative to the engine speed. The alternator/dynamo should be fitted with a 2.2 MFD
capacitor which should be connected between the +B lead (usually the thickest lead) and
the car chassis or body of the alternator.
SUPPRESSING THE IGNITION COIL
TO IGNITION 12 VOLT
1 MFD CAPACITOR
TO CONTACT BREAKER CB–
COIL
P. 29
