--Yeah, it would be "neat" to use FM on HF bands, but I have no idea if my Yaesu FT-857D will do it (at work and don't have manual here). As long as it took up no more bandwidth than a traditional AM signal, it would be fun. Not sure what modern rigs are actually capable of a modulation index of less than 1. I'm not sure if "FM-N" (FM Narrow) that are in many HF rigs, has a modulation index of less than 1.
We make a living by what we get, we make a life by what we give. --Sir Winston Churchill