Jeff, the "math" is this: the composite AM waveform crest is approximately two times (double) at full 100% modulation to what it is with no modulation. Power = E^2 / R (that's E squared) A two-times increase when squared is four times (2^2 = 4). simple enough. Notice I said "composite AM waveform." the carrier DOES NOT vary under modulation! 73 Mike - WA5CMI