On Sat, 06 Mar 2004 23:35, Patrick Dunford wrote:What do you mean by "it is not possible". If you have more than one building on a site then there must be cabling betwen them. On the sites I refer to all the buildings are easily within the 100 metre limit for each leg.
Christopher Sawtell wrote:
Got caught by the flippin' Reply-To: again. SorryWhat can cause noise on network cables?
---------- 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.
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.
I remember that the site where they are having recurrent problems has a cordless phone with a roof mounted antenna to give it an extended range. But the wiring runs under the building.
How can you detect noise? is there equipment that can be tested for it?
I know there can be earth loop problems with computers, but I haven't really delved into the technical details of it.
