This experiment started after a phone conversation with Charles Brain, G4GUO, where we had been discussing various data modes used by the military and other commercial users on the HF bands. One of the modes that has been in use for several years is digitised voice, transmitted in a bandwidth comparable with normal analogue voice communications and making use of existing transmitters and receivers. I must have said something like "it would be nice to try this on the amateur bands", because after the phone call finished Charles then went away and had a long think.
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