This may sound like a stupid question but I have spent most of my time as a licensed ham operating mostly CW and a little Phone. I became interested in the digital modes after seeing PSK-31 in operation on Field Day. Now if I understand correctly PSK-31 is operated on USB and RTTY on LSB leading to my question. What modes can you operate while in FSK mode ? I did some VHF Packet radio back in the 1980's and that is the extent of my Digital experience. So without turning on the flame thrower can someone please answer my question ?