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VE2HAR > MT63 11.03.05 15:31l 77 Lines 2178 Bytes #-7493 (0) @ WW
BID : 35117SENTTO
Read: GUEST
Subj: Re: [MT63] 20 kHz wide Digital Proposal (Was: ARRL MUST GET
Path: DB0FHN<DB0RGB<DB0MRW<OK0PPL<DB0RES<ON0AR<VA2HAR<VE2HAR
Sent: 050311/1321z @:VE2HAR.#MTL.QC.CAN.NOAM Laval #:41332 $:35117sentto
Tomi Manninen wrote:
>On Thu, 10 Mar 2005, David Willmore wrote:
>
>
>
>>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.
>
God. It just yesterday that I read the Bell Labs paper Shannon
wrote. Later I taught other EE students about bandwidth and power. Then
came spread spectrum and now your cell phone uses that plus a wide signal
> 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.
>
>
>
Yes MT63 is a good example of broad band transmission and buying S/N
at the receiver. It really works. We use it every day.
>Of course, more information needs more power if everything else is kept
>constant, so I'm not saying 56kbps is very feasible on HF...
>
>
>
I think the proper thing to say is that 56k can be sent over HF but
it's not certain what the bandwidth will be to support this baud rate.
And making it work on 6 Meters doesn't mean it will work at 20 meters.
karl
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