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What is FM diversity?

Discussion in 'Gen 2 Prius Audio and Electronics' started by Twiddles, Dec 8, 2005.

  1. Twiddles

    Twiddles New Member

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    Did a search here and can't find an answer. I have an 05 with the JBL 6 CD changer, cassette and FM DIVERSITY. Specifically (easy answer please) what is FM diversity as opposed to non-diversity?

    If it has to do with providing better FM reception, I can tell you that I have a Pioneer portable XM radio that I take in the car and have tried both the cassette adaptor (supposedly preferred method) and also tried using a wireless FM frequency. I honestly cannot tell the difference. Both methods seem to work quite well. At this point I prefer using the wireless FM transmitter that is built into the XM radio so I have one less wire hanging around. The XM satellite antenna is just sitting on the dash. Of course I have tons of antenna wire bundled up and sitting on the floor. Would it be safe to cut the antenna wire to shorten it?

    Would the AIC-100 or some other aux input solution provide even better sound quality? Any recommendations will be appreciated.
     
    #1 Twiddles, Dec 8, 2005
  2. keydiver

    keydiver New Member

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    My memory of FM Diversity is that it is a system that uses 2 antennas, the signals of which are compared by the tuner. I believe it is a method to cancel out multipath interference, from reflected transmissions.
     
    #2 keydiver, Dec 8, 2005
  3. tumbleweed

    tumbleweed Senior Member

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    Diversity in communications usually means that your receiver receives two or more signals carrying the same information (music, voice, etc.). The signals could be at different frequencies, phases, or locations in space (i.e. two antennas as mentioned above). Your receiver has some circuitry that chooses one of the received signals. It could simply pick the strongest (not always the best) or it could be more complex and actually try to determine signal quality and choose the best one.

    The length of the antenna wire is not critical. But you must put the connector (if there is one) back on properly.
     
    #3 tumbleweed, Dec 8, 2005
  4. jwe8f

    jwe8f New Member

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    No, no, it just means the radio is very receptive to alphabetic diversity, where Fs and Ms can co-exist in peaceful unity. :lol:

    Actually, you guys have it right... :)
     
    #4 jwe8f, Dec 8, 2005
  5. Tempus

    Tempus Senior Member

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    Air America and Rush Limbaugh on the same Station
     
    #5 Tempus, Dec 8, 2005
  6. jwe8f

    jwe8f New Member

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    Now that's a great example of FM diversity! :lol:
     
    #6 jwe8f, Dec 8, 2005
  7. c4

    c4 Active Member

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    FM diversity is more a gimmick than anything else.. Given the long wavelength (90 MHz is 3.3 meters, or almost 10 feet) and the requirement that for effective spatial diversity antennas be spaced far enough apart for them to be uncorrelated (generally, 2+ wavelengths, although in certain heavy multipath environments where angle spread is high, even fractional wavelength spacing has been shown to be somewhat effective, however this is the exception vs. the rule), it's really impractical for use on an automobile...

    There are a couple other means of acheiving diversity at this frequency: polarization and pattern.. Pattern diversity is basically not usable as it requires that the FM station changes its manner of transmission (ie, no longer FM, and no longer compatible with existing radios). Polarization can be used without requiring large physical separations, but it is basically ineffective as the FM signal is transmitted unpolarized, and the use of a polarized receive element immediately loses you 3dB or 50% of your signal before you even begin..

    In other words, as I already stated, FM diversity is nothing more than a gimmick..
     
    #7 c4, Dec 8, 2005
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