On 1 Oct 2005 20:54:02 -0700, wrote:

i guess i was trying to find out how many ways signal can be modulated.
even if the signal is digital, isn't it still modulated in fm?
Actually most digital schemes use PM (yes there is such a thing, Phase
Modulation). At low modulation indices, with FM, you get Narrow Band
FM, which is mathematically the same as AM with about 25% modulation.
You can carry a lot more information more easily in a given bandwidth
with PM than you can with FM.