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calculating wattage

Discussion in 'Networking Issues' started by crawdaddy, Oct 19, 2005.

  1. crawdaddy

    crawdaddy Network Guru Member

    I want to keep below the FCC law of 1 watt of broadcasting power. what's the formula, or does someone know of an online calculator that I can plug in wattage and antenna gain and get my total wattage? Thanks
  2. crawdaddy

    crawdaddy Network Guru Member

    I found a site with a few wireless calculators on it, but I don't think they are what I need.


    I want to be able to say something like xx milliwatts that the WRT xmits, times a 10db antenna equals how many watts or milliwatts coming out of the antenna. Any help?
  3. craig_oz_land

    craig_oz_land Network Guru Member

    Near enough is good enough.

    The formula for power is

    db = 10 log (P1/P2)

    You can make a spread sheet with the formula and use it for a number of different configurations.
  4. crawdaddy

    crawdaddy Network Guru Member

    the formula itself make sense, but what does the P1 and P2 stand for. I'm guessing power, but what power where? ty for the formula btw
  5. craig_oz_land

    craig_oz_land Network Guru Member

    P1 and P2 can be power in and power out. It is the ratio of the two that gives you the dB figure. If you mix up the bigger and smaller power values you will end up with a negative in front of the dB figure but same result.

    Just a matter of re-arranging the formula it to give you the form you want.

    So formula is

    db = 10 log (Pout/Pin)

    re-arrange formula for Pout

    Pout = Pin x (10 power (db/10))

    Pout will be your effective radiated power (ERP).

    dB will be in this case the gain of the antenna

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