Range of ethernet?

[cupoftea]

Hi,
I have a guy whose 55 metre ethernet cable connection was working for a day then went down.
Its porting telemetry data, not images.

I know ethernet is good to 100metres, but isnt it the longer it is, the more prone to noise it is?

 

[Prototyp_V1.0]

Well, it depends on several factors, among:

• Type of cable (cat5e or higher), is it shielded?
• What kind of termination of the cable?
• What devices are connected to each end of the cable?
• Are there different ground potential on each side? If yes and if the return current is high, that can certainly put the devices out of service.
• Environment that the cable goes through - does it goes past sources that make much noise? Is it put under ground, and does it intersect a place where it's exposed for pressure, in particular from car tires?
• An ethernet cable should not bend too sharp (around corners). Is there any lengths of the cable that is only suspended by itself, or goes over a sharp edge ?

 

[betwixt]

The length limitation isn't because the signal degrades over distance or becomes more prone to interference, although these both are real factors. The limit is because of the transit time of the data, when the length exceeds about 100m (~300') the round trip delay of data and acknowledgement becomes too long.

All the signals are differential so they have good noise immunity and they are isolated from ground at both ends so ground loops shouldn't be a problem. Certainly, sharp bends or anything else that could cause a change in impedance will cause problems.

Brian.