K8VT wrote:
The difference comes in at the radio, where the signals
dscribed above can be processed by your radio in
THREE different manners (although most radios do not
have all three modes).
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Actually, there is a fourth mode which is probably used
more than all the others put together. That is to take
the two audio tones and use them to MODULATE a carrier, either
AM or FM, as opposed to using them to create a frequency-shifted
carrier. This method is what was originally called AFSK, and is
used for VHF FM packet even now. As far as I know, this
mode has disappeared from HF - there may be some hard-core types
using it on 10, but I have never heard it myself.
Over the years, AFSK has come to mean the use of audio tones
no matter how it's done, but purists are aware that
what we now call AFSK and FSK are essentially identical,
whereas the original mode called AFSK was something entirely
different.
A bit of trivia to glaze the eyes. <g>
Bill, W7TI
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