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Thread: How do we get a radio signal as it is?

  1. #1 How do we get a radio signal as it is? 
    Forum Freshman Sudhamsu's Avatar
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    I am just studying about waves, and I have this interesting question (well, interesting for me). We know that there are many radio stations transmitting their channels at different frequencies. We get distinct sounds at different frequencies on our radio set. Shouldn't interference between different radio waves cause disturbances?


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  3. #2  
    Moderator Moderator Janus's Avatar
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    If the frequencies of the radio stations are too close to each other, then yes, there would be interference. This is why the FCC assigns staion frequencies according to location; They make sure that the frequencies of the broadcast stations that are within range of each other are sufficiently separated to prevent this.

    The reason you don't get interference from the other stations is that your radio has a tuner which filters out any radio waves not within a narrow band from the station you wish to listen to. So when you tune your AM radio to 620Khz, the tuner only lets through the radio frequencies close to 620 khz and blocks the rest.


    Sometimes at night you will get interference with AM radios. This is caused by the fact that the bottom of the ionosphere is higher at night. Radio waves can bounce off the ionsphere and thus reach areas that would normally be blocked off by the curve of the Earth. The higher ionosphere allows the waves to bounce further around the curve. This is called "skip".

    When skip is in effect, radio stations that are normally out of range of each other can be in range of each other, and if the frequencies of these stations are close enough, there will be cross interference.


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  4. #3  
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    There are different type of modulation used by broadcasting stations. Famous ones are AM, FM, and PSK.


    AM is Amplitude Modulation. FM is Frequency Modulation. PSK is Phase-Shift-Keying.

    Read on these stuff. You'll the difference and how they could interfere with each other.

    This topic is indeed one of the interesting topics in wave theory (as you go higher in frequency).
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