My first experience of HF data modes was in the 1980s was as a Short wave listener decoding RTTY (Commercial and amateur) using a Microwave Modules decoder fed into an old black and white portable TV. Many years later, as a licenced ham I used a PK232 terminal, mainly on RTTY again, but I also recall dabbling in AMTOR and even monitoring some HF packet.
These days with PC soundcards taking care of most of the decoding all we need is a simple interface between radio and PC and we can transmit and receive so many different digital modes.
In this respect perhaps I am a little lazy as the only Digi Mode I really use at the moment is PSK31. I do from time to time notice other modes in the "waterfall" display, particularly OLIVIA with its distinctive sound. Recent entries by some of my fellow bloggers have inspired me to Download the FLIDGI software and try to see if I could find some OLIVIA contacts.
So far I have limited success I have managed to decode a few OLIVIA QSOs but it seems quite difficult to determine what particular settings the are being used e.g 8/250, 8/500, 16/500 etc- is there a standard setting I wonder? Most times I cannot find the settings in use so can't get a decode. This morning, before leaving for work I even saw a very wide looking signal on 20 metres using 32/1000.
This leads me on to the number of different digi modes available. Just look at all the modes listed on Flidgi. Just as an experiment a couple of evenings ago myself and another local amateur found a quiet spot on a dead 10 metre band and ran through a couple of the modes to see how they worked.
We tried OLIVIA, FELD-HELL and THROB. FELD-HELL in particular was a very interesting mode. Its output on the screen looks almost like a FAX printout. I believe by the way that HELL is a shortened version of the proper name HELLSCHREIBER.
I wonder what the advantages of each of these modes is? It would require some time to familarise yourself with each of these modes and their advantages. Yet in the meantime new modes are being developed- all quite confusing.
Myself the only modes I really hear on HF( I am not counting SSTV and the digital DRM version) these days are PSK, OLIVIA and RTTY, but maybe other modes are in use. Does anyone use HELL on HF now, and what ever happened to AMTOR and PACTOR?