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Little more advanced FM Diversity for Car questions

Discussion in 'General Electronics' started by Eric, Feb 11, 2004.

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  1. Eric

    Eric Guest

    Hi everybody, I have basic knowledge about electronics. And I've used
    diversity reception items before (2 of my cars have it, I've also used
    wlreless mics with it in the PA market). Anyway, the 2 cars in
    question are a 97 Nissan Maxima and a 98 Chevy Corvette. The maxima's
    is fairly straight forwards, it uses one mast, one in the glass. The
    antenna connector on the OEM radio is a double plug style. When I
    used to have an aftermarket unit in there, I just bought an adaptor
    and plugged it to the mast antenna as it seemed to work better most of
    the time. Obviously here, all the processing, switching etc gets done
    inside the OEM headunit.

    Now, heres the car I'm working on now. The 98 Corvette has 2 in the
    glass antennas. The wires go into a seperate box thats behind the
    drivers seat sorta on the B pillar. This is obviously the switcher
    box, as theres also a plug that appears to go back to the OEM radio.
    I of course have lost this OEM radio long ago and put in an
    aftermarket. but the reception has been notably poor. This is most
    likely because there is no 'feedback' which is probably done inside
    that OEM headunit which isnt there anymore.

    Even with the OEM headunit, when I'd turn on the rear defrost the
    radio would go to static. I attribute this to something wrong with
    either the box or grounding or something along those lines.
    Also interesteing is that the 2 'inputs' of that box are the standard
    motorola style plug, where as the output is then the GM mini plug.

    I have not tried anything yet, but I plan to bypass this box
    completely, by just getting a antenna extension and directly plugging
    it into either the front or the rear antenna. I'm crossing my fingers
    big time to see if it does better then what I got now. I know that
    simply wiring them in parallel is a no no.

    Heres my question, does anybody make (or have a project kit) that can
    give me the diversity reception back? I have searched the groups and
    the net and have come up with very limited information. I know delphi
    (the maker of the OEM antenna system in the corvette) has some stuff
    but it is unclear if thats OEM stuff or aftermarket stuff.
  2. A true diversity system would be one that can use a reference from the
    output of the radio's detector, and select the proper antenna
    combination for the best reception. The antenna control unit would
    require a reference for the exact station being tuned. This is the
    reason for a reference to that particular signal. An external box
    with no reference, would not be very effient.

    A simple way you can have some effect of diversity, would be to put
    the two antennas in parallel through a splitter. I have done this, and
    it was improved over having one antenna.

    You can try this just to see how it works for you.

    Jerry Greenberg
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