I was trying recently to figure out why 2Vrms is 6.02 dBV instead of 3.01 dBv, and I learned that it is of course because the power in constant-load circuit is proportional to the square of the voltage. So,

dBV = 20 * log (Vmeas / 1V)

Here's my question: Does the same thing apply to dBm? If 0dBm is 1 milliwatt into a 600 ohm load, then is 2 milliwatts into the same load 3.01 dBm or 6.02 dBm?

Here's a good explanation of dB in general (tho it doesn't quite get to my question):

http://en.wikipedia.org/wiki/Decibel

Thanks,
RR