On 31/07/18 13:47, Terry Casey wrote:
In article , lid
says...
On 31/07/18 11:33, Terry Casey wrote:
In article ,
lid says...
FTTC gets you 80 if you're lucky, and more likely a lot less if you
aren't next to the cabinet.
That doesn't apply to VM FTTC, though, as the coax
distribution from the cabinet maintains its full 750MHz
(typically) bandwidth throughout the entire coax network so it
doesn't matter where on that network you are connected.
Mmm. There is a length limit on coax though
Yes and no.
There is a distinct difference between a coax network and a
length of coax.
True, signals will be attenuated along the length of the coax,
as with any other type of transmission line, particularly at
the higher frequencies but, at intervals along the route,
amplifiers restore the level and pre-equalise the levels for
feeding the next section so, within limits, levels across the
band are controlled throughout the length of the netork.
Also, the quality of the network is defined in a British
Standard which forms part of the cable operator's licence
terms.
Thus the signals fed to any subscriber on the network will
conform to tightly defined limits which ensure that all
subscribers receive the same level of service.
That is something that BT's copper network cannot do.
It could. Line powered ADSL repeaters every 2km would have gootten
everyone up to speed.
But the point is that copper twoisted pair and coax are the same. At
distance the signals are so atteneuated that bandwith foes down withiout
repeaters.
Most virgin is fibre to the cab and coax to the premnises. No repeaters
Coax is just a bit better up to say a km
--
Future generations will wonder in bemused amazement that the early
twenty-first centurys developed world went into hysterical panic over a
globally average temperature increase of a few tenths of a degree, and,
on the basis of gross exaggerations of highly uncertain computer
projections combined into implausible chains of inference, proceeded to
contemplate a rollback of the industrial age.
Richard Lindzen