----- Original Message -----
Sent: Sunday, January 10, 2010 10:49
PM
Subject: Re: LF: WSPR, QRSS, CW...
There is an absolute limit to signalling efficiency, determined by
Shannon in 1948 of -1.64dB S/N (normalised bandwidth) WSPR/WSJT
are within about 3 - 4dB of the limit, so we'll only ever get this
improvement to play with. Of course, we can go narrower and
narrower and longer and longer, but there comes a point where the
ionospheric path just won't support the signalling any more
And that's it. All that's left is more EIRP, directional Rx
antennas, noise cancellation and...
For the signal in noise story, see if you can find a copies of :
"Communication in the Presence of Noise", CE Shannon, Proc.
IRE (now IEEE) January 1949
which is the seminal paper that sets the -1.64dB S/N limit
--- and ---
"Poisson, Shannon and the Radio Amateur" , JP Costas, Proc IRE,
December 1959 which spells it all out in a delightfully readable
way
Most human modes, morse and QRSS, and Hell all come out at a roughly
similar normalised S/N, and machine modes, at the moment roughly 4 - 6dB
better than the best humans ops. As shown,
coding could further improve things by another couple of dB.
So who's going to be the first with MFSK Turbo coding on LF.
?
That's real Amateur Radio as far as I'm concerned.
Not faffing about struggling to dig tones out of noise or looking for lines of
different coloured dots
What
will happen if in 2 years the next software will be available with even much
better error correction and so on? What, if this software is so good that a
QSO to VK will be
possible?
