Instead of using the 2FSK300 mode of conventional packet, they use a substitute 15 tone QPSK running at ~83 baud with 125 Hz separation of tones.
Packet has a lot of value in terms of the framework that I often mention, but the modulation is often extremely difficult for HF and this has been known for several decades. I have never understood why the HF packet operators never seemed that eager to change to any other modulation, not even at least slowing the baud rate down to a more realistic value that could work much better, not only for sensitivity, but also for handling the ISI which is likely what prevents a 300 baud signal (with no training pulses) from working well, even with very modest amounts of multipath. The RTTY contest is keeping 20 meters quite busy a the moment although the Mexico RTTY Interntional Contest should end by 1800Z today. 73, Rick, KV9U Andy obrien wrote: > I am coming late to this topic, how is this different from regular > packet ? > > Andy K3UK >
