If Nyquist is the governing limit, how do computer modem designers
get 56 kbps through a 3 khz telphone line? That's a C/B of more than
18.
73,
Dave, AA6YQ
--- In digitalradio@yahoogroups.com, Tim Gorman <[EMAIL PROTECTED]>
wrote:
>
> No, the claim I am investigating is concerning a statement that
there is a
> need in amateur radio for a new mode with a symbol rate of
5600baud and a
> bandwidth of 2400hz.
>
> I'm very interested in how such a feat can be accomplished.
>
> I'm with you. My first thought is that such a thing would be
impossible
> because of Nyquist.
>
> But I thought I would ask to see if someone knows of a new
development in the
> Electrical Engineering field that has invalidated Nyquist.
>
> tim ab0wr
>
> On Saturday 28 January 2006 22:41, Michael Keane K1MK wrote:
> > At 10:32 PM 1/28/06, you wrote:
> > >Respectfully, you are talking about compressing the content.
That won't
> > > help with cramming a 5600 baud circuit into a 2400hz
bandwidth. It might
> > > help send more content faster - making a slower circuit "look"
like a
> > > 5600 baud circuit, but it won't help put a 5600 baud circuit
into a
> > > 2400hz bandwidth.
> > >
> > >Anybody else got any ideas?
> > >
> > >tim ab0wr
> >
> > One encounters a fundamental problem with Nyquist in attempting
to
> > use a signaling rate that's more than twice the baseband
bandwidth.
> >
> > If the baseband signal is then translated to RF with a balanced
> > modulator, the occupied bandwidth doubles. In this case a
signaling
> > rate equal to the occupied RF bandwidth, i.e. 2400 baud for a
2400 Hz
> > bandwidth, is the limit.
> >
> > That said, it's readily possible to fit a 5600 bit per second
data
> > stream into a 2400 Hz bandwidth by picking a modulation scheme
that
> > has a bandwidth efficiency of greater than 2.33 bits/s per Hz; in
> > this case, 8-PSK at a signaling rate of 1867 baud is but one way
to
> > send 5600 bits per second over a 2400 Hz BW channel.
> >
> > 73,
> > Mike K1MK
> >
> > Michael Keane K1MK
> > [EMAIL PROTECTED]
> >
> >
> >
> >
> >
> >
> > Need a Digital mode QSO? Connect to
Telnet://cluster.dynalias.org
> >
> > Other areas of interest:
> >
> > The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/
> > DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy
> > discussion)
> >
> >
> > Yahoo! Groups Links
> >
> >
> >
>
Need a Digital mode QSO? Connect to Telnet://cluster.dynalias.org
Other areas of interest:
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DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy discussion)
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