One of the main goals of radio experimentation is to see how much data you can transmit reliably over a very narrow bandwidth channel. There is also a lot of work being done on slow data transmission using ultra-low power over very long distances (they guy who spearheaded this was the same guy who developed the radio system for the Voyager satellite - Joe Taylor K1JT)
One holy grail is to be able to digitize speech (which otherwise takes a very large bandwidth) and find a way to transmit the binary digits and reconstitute it on the receiving end. There are a couple systems that work really well but they are commercial and proprietary and $$$. Australian David Rowe just figured out the holy grail and is making it open source and free.
Check out CODEC 2 700C
Codec 2 700C
My endeavor to produce a digital voice mode that competes with SSB continues. For a big chunk of 2016 I took a break from this work as I was gainfully employed on a commercial HF modem project. However since December I have once again been working on a 700 bit/s codec. The goal is voice quality roughly the same as the current 1300 bit/s mode. This can then be mated with the coherent PSK modem, and possibly the 4FSK modem for trials over HF channels.
I am not going to quote any more - you can read more at his website. Sufice to saw, this is really interesting and I will be playing around with it as soon as I get a couple other projects banged out. And, oh yes, it runs on Raspberry Pi computers. Perfect for portable work. David's About page is here.
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