<VV> radio noise

[Larry Forman]

Hi Dorai,
Your first problem is the brand.  Simply throw it away!

Some more helpful information might be:

You don't mention if the AM radio receives stations normally, once the engine is off.  If so, then it is simply a matter of eliminating this engine noise.  Typically engine noise comes from one of two sources and is "received" by the radio in two distinctly different ways.  First, is a popping noise that changes with engine rpm.  This is electrically radiated ignition noise and is typically received by the antenna and fed into the radio.  You can identify this source of noise by tuning to a clear space on the upper end of the radio dial and turning up the volume.   You should only be receiving noise in the absence of any signal.  Turn on the engine and listen to the volume of the noise.  Now pull the radio antenna plug ouf of the back of the radio.  If the noise goes down a LOT or becomes faint or non-existent, then the noise is being radiated into the antenna and fed to the radio through the antenna lead.  Typical solutions are to replace any faulty condensors, and there should be one on the positive lead of the ignition coil as well as at the points, replacing old or faulty spark plug wires, cap or rotor, or shielding the ignition components.

If removing the antenna lead has no effect then the electrical noise is likely being conducted into the radio through the 12 volt supply leads, and that is normally a "whining noise".  You can identify the source of the noise by temporarily removing the fan belt and starting the engine and listening for the noise for a SHORT time  before shutting down the engine.  This prevents the alternator or generator from rotating and generating any electrical noise.  If the noise stops, then the source was one of those.  Solutions are typically to add either a condensor or line filter at the source and/or at the radio, or replace generator brushes or clean alternator slip rings.  It is normally better practice to suppress any noise at the transmitter (alt/gen) rather than shielding many potential receivers (AM radios).

HTH,

Larry  


----- Original Message -----
From: "Dorairaj Isaac" <dnaisaac at sympatico.ca>
To: VirtualVairs <VirtualVairs at corvair.org>
Subject: <VV> radio noise
Date: Fri, 26 Aug 2005 10:39:32 -0400

> 
> Hi,
> I have an older Radio Shack cassette radio in my car.  The radio plays well
> in FM but make a great deal of noise in AM only when the motor is running.
> When the motor is turned off there is no noise.  What can I do to suppress
> the noise.
> Thanks in advance.
> 
> Dorai <><
> 
> 
> 
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