Technical aspects of automobiles

Car-radio disturbance – educate me.

I have a basic problem with my car radio and was wondering if someone
can diagnose it, for it seems quite elementary though out of my
domain.

The issue is disturbance.  I turn on the ignition and tune the radio
to a local station.  No problem.  Radio is clear, sound quality crisp.
Now I start the engine.  This introduces a continuous disturbance that
varies with rpm (sonic frequency?).  The problem is magnified the
further I am from the transmitting station, i.e. as the signal get
weaker.  (Begins to sound like the motor’s inside the passenger
compartment!)

I have an antenna built into the windshield.  I haven’t looked at the
connectors to the antenna.  I don’t believe that this is relevant as
the radio sounds good when the engine is off and when the signal is
strong.  Is there some sort of "suppressor" (frequency?) that I’m
missing?  That I can buy?  I just bought this car and have no history.
In case this is pertinent, the car is a 1982 Celica GT and there is no
problem with the tape deck.

Thanks,

–Vijay

———————————————————————-
Vijay Sundaram                 vi…@apollo.hp.com
Hewlett-Packard Company        Phone:(508) 256-6600 x4191 TN: 256-4191
______________________________________________________________________

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posted by admin in Uncategorized and have Comments (3)

3 Responses to “Car-radio disturbance – educate me.”

  1. admin says:

    - Hide quoted text — Show quoted text -

    In article <1992Jan10.152431.11…@apollo.hp.com>, vi…@apollo.hp.com (Vijay Sundaram) writes:
    > I have a basic problem with my car radio and was wondering if someone
    > can diagnose it, for it seems quite elementary though out of my
    > domain.

    > The issue is disturbance.  I turn on the ignition and tune the radio
    > to a local station.  No problem.  Radio is clear, sound quality crisp.
    > Now I start the engine.  This introduces a continuous disturbance that
    > varies with rpm (sonic frequency?).  The problem is magnified the
    > further I am from the transmitting station, i.e. as the signal get
    > weaker.  (Begins to sound like the motor’s inside the passenger
    > compartment!)

    > I have an antenna built into the windshield.  I haven’t looked at the
    > connectors to the antenna.  I don’t believe that this is relevant as
    > the radio sounds good when the engine is off and when the signal is
    > strong.  Is there some sort of "suppressor" (frequency?) that I’m
    > missing?  That I can buy?  I just bought this car and have no history.
    > In case this is pertinent, the car is a 1982 Celica GT and there is no
    > problem with the tape deck.

    > Thanks,

    > –Vijay

    > ———————————————————————-
    > Vijay Sundaram                 vi…@apollo.hp.com
    > Hewlett-Packard Company        Phone:(508) 256-6600 x4191 TN: 256-4191
    > ______________________________________________________________________

       I worked at an auto parts store for several years and encountered
    this question quite often.  I never found anything to completely
    suppress the engine sound, but came close.  We sold many antennae
    filters which basically were good for nothing.  The best think I found
    was a type of condensor, similar to condensors found on points.  This
    condensor is made to fasten on to the back of the alternator at the
    positive battery connection.  The sound you are getting sounds like it
    is coming from the alternator.  This item has worked well on some
    vehicles and not at all on others.  It wouldn’t hurt to try it seeing
    that it only costs around $2.00.  
       When I worked at the parts store, we carried this product in our
    IGNITION parts line.  The brand of the part was called WELLS.  I am
    sure that there are some other brands which carry similar items.  If
    the parts salesperson acts as if he has no idea what you are talking
    about, ask to look in the back of the parts book.  Nearly every parts
    book has pictures in the back for technical identification.  Look under
    the Points and Condensors section.  Be very careful when installing
    the item.  Be sure to disconnect your battery before you do anything
    as you will receive a nice big bad ugly jolt if you don’t.  Once again
    this may not solve your problem, but it is a cheap way to start.
    Good Luck!!!!!!

    These comments are suggestions only.  Not respnosible for accidents.
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  2. admin says:

    Radio Shack also carries these noise suppression capacitors.  Is the sound
    a fast "ticking" (comes from the spark plugs), or a "whine" (comes from the
    alternator)?  Is the problem just when tuned to AM, FM, or both?  AM is much
    more susceptible to spark plug noise, especially when tuned to a weak station.
    For spark plug noise, use resistive spark plugs or resistive plug wiring (or
    both).  For alternator whine, use the capacitor on your alternator.  Is the
    radio an "add-on"?  Sometimes running the power wires directly to the battery
    will reduce the interference.

  3. admin says:

    In article <1992Jan10.152431.11…@apollo.hp.com> vi…@apollo.hp.com (Vijay Sundaram) writes:
    >I have a basic problem with my car radio and was wondering if someone
    >can diagnose it, for it seems quite elementary though out of my
    >domain.

    >The issue is disturbance.  I turn on the ignition and tune the radio
    >to a local station.  No problem.  Radio is clear, sound quality crisp.
    >Now I start the engine.  This introduces a continuous disturbance that
    >varies with rpm (sonic frequency?).  The problem is magnified the
    >further I am from the transmitting station, i.e. as the signal get
    >weaker.  (Begins to sound like the motor’s inside the passenger
    >compartment!)

    I had posted this article some time ago and received a few suggestions
    most of which have already been publicized here.  

    The solution was unanticipated – a new water-pump!  Well, my car
    needed a new water-pump as the last one was waiting to die on me; I
    could hear the bearings groaning all the time, making the engine sound
    really unhealthy especially at low rpm.  I changed this over the
    week-end and the radio interference was gone!  Atleast, I did not
    notice it today even when the radio signals were relatively weak.  Any
    theories?

    –Vijay

    PS: Thanks to all the suggestions; I did learn quite a bit.  BTW, I
    did have resistive spark-plugs and wires.  Someone on the net asked me
    if it was a fast "ticking" or a "whine" (by his analysis, suggestive
    of spark-plugs and alternator interference respectively).  Mine was
    definitely a fast "ticking".

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