under unlicensed 2.4GHz FCC part 15 for digital modulation
system(non-spread spectrum), it says that the
1. maximum conducted power is 1W
2. the spectral density be not greater than 8dB for every 3khz band
during continous transmission
3. the 6-dB bandwith is at least 500khz

question:
1. what is spectral density in this sense and its significance?
2. how can i measure my spectral density?
3. how does 1, 2 and 3 relate to each other?