Message-ID: <3A938052.F6EB7425@netscapeonline.co.uk>
Date: Wed, 21 Feb 2001 08:46:10 +0000
From: "gii3kev" <gii3kev@netscapeonline.co.uk>
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To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: RE: Where next?
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Talbot Andrew wrote:

> Mike's comments still seem to make the assumption that a human brain can
> do better than software.  Why ?
>
> It doesn't matter how good your eyes are at perceiving subtle
> differences of tone or colour interspersed with static crashes, or ears
> at hearing minute changes in a single tone, they can only see / hear
> amplitude changes and are throwing away all the information contained in
> the phase of the signal - 3dB worth if your interpretation is perfect
> and probably a lot more.
>
> Why assume a machine cannot do better - the world is now full of
> communication signals travelling over links that would be impossible for
> analogue information.  We just need to choose a scheme optimised to the
> type of signalling we want to do and write software to implement it in
> such a way that the average amateur (who won't build anything of course)
> can just plug in and go.
>
> It is very arrogant to assume the human brain can always do better than
> a machine just because we feel it ought to.
>
> PSK will do better on LF than SLOWCW  DFCW etc. in similar bandwidths,
> but we need to implement it properly.  The US Lowfers are there, and
> showed this years ago.  All we need is decent frequency stability in
> receiver and transmitter and a preparedness to not insist on relying
> blindly on Soundcards to meet all our data comms needs.
>
> If the link won't support lower and lower bandwidths - the simplest
> route to weak signal working - then use coding to achieve this with
> wider signals.  And here only machines can do the job.   I can't somehow
> visualise a human brain doing the Viterbi error correction algorithm in
> real time from a Spectrogram
> --------
> I understand there was a quote published in QST (or QEX ?) some time ago
> from the FCC to the ARRL that "If amateurs did not improve their
> technology they would lose spectrum".    Can anyone in the US confirm
> (or deny) this and point me at the reference.

They have been saying this and scare mongering for as long as I can
remember but
in fact we have been allocated more radio spectrum and NOT LESS. This is
an old
Chesnut!!!!!!1 Dont fall for it !!


>
>
> Andy  G4JNT
>
> > -----Original Message-----
> > From: Mike Dennison [mailto:mike.dennison@rsgb.org.uk]
> > Sent: 2001-02-19 16:37
> > To: rsgb_lf_group@blacksheep.org
> > Subject: LF: Where next?
> >
> >
> >
> > > ..................... One such candidate could be the Steve
> > Onley's FDK.  I
> > > know that, theoretically, PSK can have an advantage over
> > non-coherent
> > > FSK, but this doesn't take into account phase distortion over very
> > > long paths.  But I will leave to others to discuss about
> > the pros and
> > > cons of the two methods.
> > > 73  Alberto   I2PHD
> >
> > A factor that is often ignored when comparing PSK08 (for instance)
> > and QRSS is the difference between relying on a machine to
> > interpret the results and using the brain. The spectrogram-type
> > programs do wonderful work but the final 10dB or so is down to the
> > brain deciding what is a valid signal and what is not, then deciding
> > whether it makes sense or not.
> >
> > We really would have a winner if we can combine the obvious
> > theoretical advantages of using FM (or phase mod) rather than AM,
> > especially when noise is a significant limiting factor, with the
> > advantages of a display that allows the brain to add some dBs by
> > intelligently interpreting the result.
> >
> > For instance, how about produce a display that is the result of
> > subtracting the signals and noise in a given audio band, with the
> > signals and noise in another band of the same bandwidth. This might
> > provide a means of reducing the effect of wideband noise such as
> > static (but not random noise) on a conventional mono-frequency
> > transmission by subtracting the noise in the 'no-signal' band from
> > the band containing the signal. It might also provide a 'comparitor'
> > effect so that FSK signals can be better detected - for a given time
> > period, if the output of 'channel A' is bigger than the output of
> > 'channel B' then it is a binary '1'; if the other way round
> > it is a binary
> > '0'.The important thing is to resist the temptation to feed
> > this into a
> > machine that tries its best to work out whether it is a valid
> > character
> > or not - this is the bit that the brain does better.
> >
> >
> > Mike
> >
> >
>
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