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Thread: What is dBm in wifi signal and understanding the best

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    Default What is dBm in wifi signal and understanding the best

    I think everyone have seen this dbm in router, 3G modem(Banglalion, qubee, olo etc.) many times. Today I will try to give you all idea about what it is and how to read the signal.



    First what is dbm ?

    dBm - This is a power expressed in decibels relative to one milliwatt.

    Which one is better ?

    -1 dBm is significantly better than -100 dBm. Thus ....

    •Excellent (green): -57 to -45 dBms (75 to 100%)

    •Good (green): -75 to -58 dBms (40 to 74%)

    • Fair (yellow): -85 to -76 dBms (20 to 39%)

    • Poor (red): -95 to -86 dBms (0 to 19%)


    How ?

    let's crack the math now.

    The reason you see negative values is that you're representing small but positive numbers, on a logarithmic scale. In logarithms, the value indicated represents an exponent... for example, under a log 10 scale, a value of -2 represents 10 to the -2 power, which equals 0.01. Likewise, a negative dBm means that you're applying a negative exponent in your power calculations; 0 dBm equals 1 mW of power, so -10 dBm equates to 0.1 mW, -20 dBm equates to 0.01 mW, and so forth. It's a lot easier, and more useful in some calculations, to describe a weak signal as -100 dBm as opposed to 0.0000000001 mW.

    The numbers are in -dbm, decibels below one milliwatt on the antenna connector.

    0dbm = 1mw
    -10dbm = .1mw
    -20dbm = .01mw
    -30dbm = .001mw or 1 microwatt
    every 10 db = a factor of 10.
    every 3 db = a factor of 1/2.
    the m is the reference point of a milliwatt.

    Now I will be needed a EEE graduate to explain it further.
    Last edited by Metal; March 18th, 2013 at 12:07.
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