Dee Flint wrote:

Please show me and everyone else how we can run more than 300
baud on HF
without exceeding reasonable band widths. There are a whole
lot of things,
not just video, that would be nice to do.

The answer (in large part) is to use different modulation and encoding
schemes. Such as QPSK instead of BFSK. Multiple carriers spaced just
far enough apart to avoid interference. Simultaneous AM and PM.

Of course such modes may not have the HF performance we're used to
from, say, PSK31 or SSB. You don't get something for nothing; Shannon's
Theorem shows that the increased data rate in a given bandwidth comes
at the price of needing more S/N to get acceptable results.

As K0HB points out, the 300 baud limit only applies in the CW/data
subbands. If you can stuff "TV" into a reasonable bandwidth, it can be
sent in the voice/image subbands.

As a simple example, imagine 25 PSK31 carriers spaced cheek-by-jowl in
a typical SSB bandwidth, running QPSK. If one gets you 100 baud, 25
will get you 2500 baud. Go to 8PSK and you get 5000 baud. Then add
compression on top of that...

How can we do it? Bandwidth is directly related to baud rate.

Only if "all else is equal". The trick is to make the tradeoff
somewhere else. The familiar "56K" modem trades off S/N rather than
bandwidth.

It's not a complex subject at all.

You've probably heard the old engineering adage:

"You can have it fast, good or cheap. Choose any two"

All Shannon's Theorem does is equate fast to data rate, good to S/N,
and cheap to bandwidth.

73 de Jim, N2EY