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Date: Sun, 10 Jan 2010 22:49:42 +0000
Message-ID: <fc7eccec1001101449i4a724340l607be147d4d1dbc8@mail.gmail.com>
From: Andy Talbot <andy.g4jnt@googlemail.com>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: WSPR, QRSS, CW...
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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

Andy
www.g4jnt.com

> 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?
>
>

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<div>There is an absolute limit to signalling efficiency, determined by Sh=
annon in 1948 of -1.64dB S/N (normalised bandwidth)=A0=A0 WSPR/WSJT are wi=
thin about=A03 - 4dB of the limit, so we&#39;ll only ever get this improve=
ment to play with.=A0=A0 Of course, we can go narrower and narrower and lo=
nger and longer,=A0but there comes a point where the ionospheric path just=
 won&#39;t support the signalling any more</div>

<div>=A0</div>
<div>And that&#39;s it.=A0=A0All that&#39;s left is more EIRP, directional=
 Rx antennas, noise cancellation and...</div>
<div>=A0</div>
<div>For the signal in noise story, see if you can find a copies of :</div=
>
<div>=A0</div>
<div>&quot;Communication in the Presence of Noise&quot;, =A0CE Shannon,=A0=
 Proc. =A0IRE=A0=A0(now IEEE)=A0 =A0January 1949=A0 </div>
<div>which is the seminal paper that=A0sets the=A0 -1.64dB S/N limit </div=
>
<div>=A0=A0</div>
<div>--- and=A0---</div>
<div>=A0</div>
<div>&quot;Poisson, Shannon and the Radio Amateur&quot; ,=A0 JP Costas, Pr=
oc IRE, December 1959=A0=A0 which spells it all out in a delightfully read=
able way</div>
<div>=A0</div>
<div>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.=A0=A0 As shown, coding=A0<u>could</u> fu=
rther improve things by another couple of dB.</div>

<div>=A0</div>
<div>So who&#39;s going to be the first with MFSK Turbo coding on LF.=A0=
 ?</div>
<div>That&#39;s <strong>real Amateur Radio</strong> as far as I&#39;m conc=
erned.=A0 Not faffing about struggling to dig tones out of noise or lookin=
g for lines of different coloured dots </div>
<div><br clear=3D"all">Andy<br><a href=3D"http://www.g4jnt.com">www.g4jnt.=
com</a><br></div>
<div class=3D"gmail_quote">
<blockquote style=3D"BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8e=
x; PADDING-LEFT: 1ex" class=3D"gmail_quote">What will happen if in 2 years=
 the next software will be available with even much better error correctio=
n and so on? What, if this software is so good that a QSO to VK will be po=
ssible?<br>
<br></blockquote></div>

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