[Elecraft] Is the K3 capable of ESSB?

[David Woolley]

Fred (FL) wrote:
> In 1978 - max bandwith over telephonic modems,
> and conditioned AT&T lines was like 6250 baud.
> A "limit" everyone agreed.

Shannon's classic paper on communications theory was published in 1948,
so, for 30 years before 1978, anyone who knew the signal to noise ratio
and did the maths would have known that that was not the limit.  What
they were probably actually saying is that that was the limit for pure
quadrature phase modulation, or, maybe for economically realisable
hardware at the time.

Incidentally, there now is a hard limit, because the telphone network
core is digital, and you cannot exceed 64kbps (or in the USA, with
robbed bit signalling, slightly less than that).  At that time, the
limit would have depended on the signal to noise ratio.  SNR would
depend on the line.

(The telcos don't allow modems to run as fast as they could, because
that would compromise the analogue parts of the network, hence a 56,
rather than 64kbs, limit.)


-- 
David Woolley
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