On Sat, 06 Mar 2004 23:35, Patrick Dunford wrote: > Christopher Sawtell wrote: > >Got caught by the flippin' Reply-To: again. Sorry > > > >---------- Forwarded Message ---------- > > > >Subject: Re: [OT] LAN cable tester in Christchurch to borrow please > >Date: Sat, 06 Mar 2004 21:12 > >From: Christopher Sawtell <[EMAIL PROTECTED]> > >To: [EMAIL PROTECTED] > > > >On Sat, 06 Mar 2004 18:00, Yuri de Groot wrote: > >>Hi, > >> > >>Does anyone have an advanced LAN cable tester I can borrow > >>in Chch? > >>I have one that tests each of the 8 strands for electrical > >>conductivity, but it does not test ability to carry ethernet > >>traffic - if ya know wha I mean. > > > >I came across a very similar situation to your's a while ago. > >After much confusion with very odd intermittent faults it transpired that > > the poorly put together Ethernet wiring would happily carry 10MHz > > signals, but not 100MHz. Sometimes the net worked ok as a 10MHz net, at > > others it failed as a 100MHz. We were confused for quite a while. After > > rewireing it properly, it worked perfectly. > > > >The point of the story is that it might be worth your while putting an old > >10MHz card in one of the machines to force your net to run at 10MHz. If it > >works at the lower frequency, then that more or less proves that you have > >problems with noise on the cable run. > > What can cause noise on network cables?
Cross-talk from the mains would be the most usual. In any situation remotely 'industrial' the mains wiring can be a real noise generator. As a previous poster stated running Ethernet close to mains wiring is usually the problem. imho, At least 50 cms in practice leave at least one stud space between them in a wall. RF from broadcasting transmitters is another source of interference. These days cell-phones are a real bane. Seen the notices in the hospitals? > I'm interested because I spend a > bit of my time each week dealing with problems in a network of about 60 > computers spread over two sites. We have had a complete failure of a 16 > port network switch, but we have also had ongoing problems with one > particular printer on the network that people seem to have recurring > loss of connectivity to. I'm planning to do some more tests with a > 10Mbps hub instead of a 100Mbps switch at that location. Faulty earthing causing earth-loops is another problem all of its own. Running Ethernet between buildings, particularly in an industrial situation, is simply not possible. -- Sincerely etc. Christopher Sawtell NB. This PC runs Linux. If you find a virus apparently from me, it has forged the e-mail headers on someone else's machine. Please do not notify me when this occurs. Thanks.
