[15:43] <SStteevvee> to convert dBm to milliwatts...
[15:43] <SStteevvee> 10^(x/10)
[15:43] <SStteevvee> where x is the dBm value
[15:43] <SStteevvee> to convert milliwats to dBm its:
[15:43] <SStteevvee> 10 log10 (x)
[15:43] <SStteevvee> log10 = log, base 10
[15:46] <SStteevvee> ummm....
[15:47] <SStteevvee> conceptual idea is that the dB scale is measuring the relative amount of something to something else.
[15:47] <SStteevvee> e.g. dBm is relative to 1 milliwatt.
[15:47] <SStteevvee> if two signals are 38dB different, that means that:
[15:47] <SStteevvee> 10 * log10 ( sig1strength/sig2strength) = 38
[15:47] <SStteevvee> sooo.... the actual difference between the two signals is 10^(38 / 10)
[15:48] <SStteevvee> = 10^3.8
[15:48] <SStteevvee> = 6310 times
[15:50] <SStteevvee> a 200mW senao card is... 10*log10(200) = 23dBm
[15:51] <SStteevvee> a 65mW card is 10*log10(65) = 18dBm
[15:51] <SStteevvee> difference is 5 dBm
[15:51] <SStteevvee> 10^(0.5) = 3.16 ... so 200mW is 3.16 times more powerful than a 65mW card
[15:51] <SStteevvee> 200/65 = 3.1  :)
[15:52] <SStteevvee> if i hadn't rounded on the way, the numbers would have been exactly the same
[15:56] <SStteevvee> one more example:
[15:56] <SStteevvee> 4W EIRP power limit = 10*log10(4000) = 36dBm
[15:56] <SStteevvee> so, if you have a 18dBm card, 3dBm of loss in cable, and a 24dBi antenna, thats:
[15:57] <SStteevvee> 18 - 3 + 24 = 39dBm output
[15:57] <SStteevvee> which is over the legal limit
[15:58] <SStteevvee> windows' caculator has a button for "log" if you turn on its scientific view/mode