FSK Hell Modes
FSK-Hell. This mode uses Frequency Shift Keying with a speed of 105 or 245 baud. The average duty cycle is about 80%. Actually this is not a new Hellschreiber mode at all - not even for amateur radio! It was actually already tested by the end of World War II
reference https://www.nonstopsystems.com/radio/hellschreiber-modes-modern.htm
