
Adding Power Levels...
Adding two power levels is easy when
using Watts or milliWatts, but adding power levels expressed in dB is not as simple!
Whereas 1mW + 2mW = 3mW, 0dBm + 3dBm (the equivalents of 1mW and 2mW) DOES
NOT = 3dBm! 0dBm + 3dBm = 4.77dBm! Also, try adding 3mW + 2dBm (3mW +
1.58mW = 4.58mW or 6.61dBm)!! The calculator below makes adding two power levels in mW,
W, dBm or dBW easy; one can even "mix 'n' match"!!
NOTE: The units of power MUST be selected before the
calculator will work.

Note that the magnitude of dBW for a given power level is always "30" less than
the magnitude of dBm. This is due to the relationship between Watts and milliWatts.
dBW = 10*logP where P = power is in Watts.
dBm=10*logP where P = power in milliWatts.
Example: Using 1W = 1000mW (1000 = 10^{3}),
dBW = 10*log1 = 10*0 = 0 while dBm = 10*log10^{3} = 10*3 = 30
Q.E.D.

An ND2X javascript calculator


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