On 08/02/2014 17:24, David Paste wrote:
As I understand it, ADSL signals are passed along the twisted pair (is
that right?) telephone cables which are the same used for voice calls.
At a much higher frequency, of course. I am also under the impression
that the length of this cable is critical for service quality and
overall data rate (apart from junction / joint quality).

Yup pretty much. There are a few different flavours of DSL technology,
and give a relatively short decent line some will get noticeably better
performance than others. However once you get to a few km of wire they
all become similar in performance.

See the graph for the tradeoff:

http://www.internode.on.net/resident...d/performance/


Would using coax for the last stretch to the subscriber's premises
provide any better quality of service?

Depends on if you mean "could the system be re-engineered to do this and
would it help" (yes, and probably not noticeably)[1], or could you just
"lashup a bit of coax in the place of twisted pair, and would that help"
(yes, and absolutely not).

So the short answer no.

I only ask as my cable service uses coax and I wondered about the
difference.

You can use co-ax or twisted pair for data transmission - each have pros
and cons but the mechanisms at play for keeping the signal in and the
noise out are different - so the electronics that drives and receives
these signals needs to be specific to the cable type.

[1] The other way round could work better; replace the miles of damp
string with co-ax and then use the damp string for the last few hundred
yards ;-)

--
Cheers,

John.

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