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VE2HAR > MT63 11.03.05 19:29l 58 Lines 1881 Bytes #-7344 (0) @ WW
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Subj: Re: [MT63] 20 kHz wide Digital Proposal (Was: ARRL MUST GET
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Sent: 050311/1705z @:VE2HAR.#MTL.QC.CAN.NOAM Laval #:41359 $:53034sentto
> > So, MT63 (63 carriers of BPSK and heavy FEC) in a 1KHz BW at -5db (in
> > the same BW?) SNR competing with a similar signal in 6KHz of BW will be
> > -12.8db SNR (in a 6KHz BW). Do you expect to be able to decode that?
> >
> > What I'm getting at is that adding bandwidth isn't a wonderful solution
> > to your problems.
>
> Please remember that you *can* trade power for bandwidth. That's what
> Shannon said over 50 years ago and most hams don't get today. You can get
> a given amount of information through with less power if you increase the
> bandwidth (ie. add redundancy: fec). Of course HF makes the situation much
> more "interesting" but it's basically still true.
>
> Of course, more information needs more power if everything else is kept
> constant, so I'm not saying 56kbps is very feasible on HF...
Tomi,
Shannon said you can do that on a stateless channel with AWGN. HF is
neither of those. In paths that are close to Shannons model--space--
they do use wider bandwidths at constant power to get their signals
through. But, they have plenty of spectrum up in microwave to do things
like that. :)
Cheers,
David n0ymv
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