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Buzz/static on AM radio?

Discussion in 'GM Electrical Tech' started by estrom, Oct 21, 2013.

  1. estrom

    estrom Member 1 Year

    What the heck causes the buzz/static when the stereo is on AM? Thanks.
     
  2. Crawdaddy

    Crawdaddy ↑↑↑ Has no life Staff Member 5+ Years 1000 Posts Platinum Contributor

    In short, electrical noise. Where the noise is coming from could be from numerous sources including power lines and the isolators on power poles, other bad electrical connections in houses and businesses, right down to plasma TVs with poorly designed power supplies. It can also potentially be caused by DC electrical interference from bad connections on the vehicle or spark plug wires that the insulation is failing on.
     
  3. estrom

    estrom Member 1 Year

    It definitely is something on the vehicle because it's there no matter where I go and it's constant. I've just put new plug wires on it so I can't imagine that being the problem.
     
  4. Enkeiavalanche

    Enkeiavalanche Rockstar 4 Years ROTM Winner 5000 Posts

    I put a HD Tuner in my truck and get most Am Stations in like FM sound...
     
  5. summitwhite11

    summitwhite11 Member 1 Year 100 Posts

    In many cases it comes thru the ignition system, alternator, leaky plug wires, (not the case here) faulty diode, and a host of other sources as mentioned, a quick 20 dollar fix can be found at the local radio shack or stereo shop, what you want is an RFI filter, with AM you can have radio frequency interference, the RFI filter will prevent that from coming thru your radio. Attaches to the radio power in, simple install. fluid filter, air filter, noise filter, man you need a filter for everything these days, lol.
     
  6. poncho62

    poncho62 Member 1 Year 100 Posts

    Basically, AM is transmitted on a lower frequency than FM and is more susceptible to interference......

    More AM/FM facts

    [TABLE="class: zebra-striped"]
    [TR]
    [TH="class: acol"][/TH]
    [TH="class: vcol"]AM[/TH]
    [TH="class: vcol"]FM[/TH]
    [/TR]
    [TR="class: comparisonRow"]
    [TD="class: acol"]Origin:[/TD]
    [TD="class: vcol"]AM method of audio transmission was first successfully carried out in the mid 1870s.[/TD]
    [TD="class: vcol"]FM radio was developed in the United states mainly by Edwin Armstrong in the 1930s.[/TD]
    [/TR]
    [TR="class: comparisonRow"]
    [TD="class: acol"]Modulating differences:[/TD]
    [TD="class: vcol"]In AM, a radio wave known as the "carrier" or "carrier wave" is modulated in amplitude by the signal that is to be transmitted.[/TD]
    [TD="class: vcol"]In FM, a radio wave known as the "carrier" or "carrier wave" is modulated in frequency by the signal that is to be transmitted.[/TD]
    [/TR]
    [TR="class: comparisonRow"]
    [TD="class: acol"]Importance:[/TD]
    [TD="class: vcol"]It is used in both analog and digital communication and telemetry.[/TD]
    [TD="class: vcol"]It is used in both analog and digital communication and telemetry.[/TD]
    [/TR]
    [TR="class: comparisonRow"]
    [TD="class: acol"]Pros and cons:[/TD]
    [TD="class: vcol"]AM has poorer sound quality compared to FM, but is cheaper and can be transmitted over long distances. It has a smaller bandwidth so it can have more stations available in any frequency range.[/TD]
    [TD="class: vcol"]FM is less prone to interference than AM. However, FM signals are impacted by physical barriers. FM has greater sound quality due to higher bandwidth.[/TD]
    [/TR]
    [TR="class: comparisonRow"]
    [TD="class: acol"]Stands for:[/TD]
    [TD="class: vcol"]AM stands for Amplitude Modulation[/TD]
    [TD="class: vcol"]FM stands for Frequency Modulation[/TD]
    [/TR]
    [TR="class: comparisonRow"]
    [TD="class: acol"]Range:[/TD]
    [TD="class: vcol"]AM radio ranges from 535 to 1705 kilohertz (OR) Up to 1200 Bits per second[/TD]
    [TD="class: vcol"]FM radio ranges in a higher spectrum from 88 to 108 megahertz. (OR) 1200 to 2400 bits per second[/TD]
    [/TR]
    [TR="class: comparisonRow"]
    [TD="class: acol"]Bandwidth Requirements:[/TD]
    [TD="class: vcol"]Twice the highest modulating frequency. In AM radio broadcasting, the modulating signal has bandwidth of 15kHz, and hence the bandwidth of an amplitude-modulated signal is 30kHz[/TD]
    [TD="class: vcol"]Twice the sum of the modulating signal frequency and the frequency deviation. If the frequency deviation is 75kHz and the modulating signal frequency is 15kHz, the bandwidth required is 180kHz[/TD]
    [/TR]
    [TR="class: comparisonRow"]
    [TD="class: acol"]Zero crossing in modulated signal:[/TD]
    [TD="class: vcol"]Equidistant[/TD]
    [TD="class: vcol"]not equidistant[/TD]
    [/TR]
    [TR="class: comparisonRow"]
    [TD="class: acol"]Complexity:[/TD]
    [TD="class: vcol"]transmitter and receiver are simple but in case of SSBSC AM carrier syncronization is needed[/TD]
    [TD="class: vcol"]tranmitter and reciver are more complex as variation of modulating signal has to converted and detected from corresponding variation in frequencies.(i.e. voltage to frequency and frequency to voltage conversion has to be done) which are quite complex[/TD]
    [/TR]
    [TR="class: comparisonRow"]
    [TD="class: acol"]Noise:[/TD]
    [TD="class: vcol"]AM is more susceptible to noise because noise affects amplitude, which is where information is "stored" in an AM signal.[/TD]
    [TD="class: vcol"]FM is less susceptible to noise because information in an FM signal is transmitted through varying the frequency, and not the amplitude.[/TD]
    [/TR]
    [/TABLE]
     
  7. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    Standard headlights, or an upgrade?

    HIDs can cause the problem.
     
  8. estrom

    estrom Member 1 Year

    Standard headlights. It's an alpine aftermarket stereo that has been working fine. The problem just came up the last few weeks.
     
  9. RayVoy

    RayVoy Well-Known Member 2 Years 1000 Posts

    The lead from the antenna to the radio is shielded co-ax. For the shield to work, the base of the antenna needs to be grounded. Perhaps you've lost the antenna ground.
     
  10. estrom

    estrom Member 1 Year

    Thanks RayVoy. I'll check that out.
     

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