Re: sharing BB between 2 houses

In article <8Mfvf.135926$Qq3.37371@xxxxxxxxxxxxxxxxxxxxxx>,
Mugwump <me@xxxxxxxxxxx> writes:
> In article <dpjv3s$g53$1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
> nospamclayton@xxxxxxxxxxxxxx says...
>
>> Traditional ethernet would go 500m, but can you still get it?
>>
> Max distance for ethernet (10Mb) and fast ethernet (100MB) is 100m. It
> may well go that distance but performance will degrade due to increased
> risk of collision.

The original ethernet (10base5) is specified for 500m, but uses such
thick coax cable - usually called "thick ethernet cable" it would be
very expensive for this distance. Transceivers to use it are probably
extremely rare too.

The later 10base2 ethernet using more reasonably priced "thin ethernet
cable" is specified for nearly 200m (185m). This would probably work
happily at 300-400m if there are only two attachments to the segment:
one at each end, properly terminated. The reduced distance compared with
10base5 was due to the higher attenuation of the thinner cable, but the
spec still allowed up to 30 attachments along the length of this cable.
Such multiple connections were a major source of attenuation - do
without that many and you can increase the distance. The spec didn't
allow it, but that was to keep the rules simple, not beacuse it didn't
work.

The main problem is getting hold of old equipment with a 10base2
ethernet interface on it - always presented as a BNC socket - and then
converting to modern 10baseT (or 100baseT). A pair of 10base2 to 10baseT
repeaters / bridges / hubs would be ideal. They're the sort of thing
that places which implemented 10base2 back in the 1980s will have been
throwing out in the late 1990s, along with the coax cable perhaps. Not
ideal for outside use, and there are safety issues to be aware of due to
differing ground potential in thunderstorms - but a reliable cheap
solution if the circumstances are right, and the old kit can be found.
A pair of old PCs, each with a 10base2 ethernet card (normally ISA slot)
and a modern 10/100 ethernet card would do as well.

Whilst collisions will occur, reducing the effective bandwidth, the
distance won't have a huge effect on this at 10 Mbps, and it should
still be more than adequate for sharing a 2 Mbps broadband connection.

The more recent twisted pair ethernets 10baseT and 100baseT that Mugwump
refers to are, of course, limited to 100m and designed only for
connecting two systems - you can't take such liberties with their
distance limits.

--
Tim Clark
.

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