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Hi Rafael:

Tom is correct in his application of the rules of 10's and 3's. I prefer to emphasize that RF gains and losses are multiplications and divisions, even when the absolute numbers representing the gains and losses have been expressed as decibels, as follows.

8 db = 10 dB x 10 dB / 3 dB / 3 dB / 3 dB / 3 dB

So 10 mW x 8 dB = 10 mW x 10 x 10 / 2 / 2 / 2 / 2 = 62.5 mW


5 dB = 3 dB x 3 dB x 3 dB x 3 dB x 3 dB / 10 dB

So 10 mW x 5 dB = 10 mW x 2 x 2 x 2 x 2 x 2 / 10 = 32 mW


I hope this helps. Thanks. /criss