[AusNOG] Cable length limits?

[Shane ONeill]

The  temperature coefficient of copper at 20c approx 0.0003 so if your impedance is 100ohms this would rise to 106ohm at 40c therefore given standard Ethernet uses 2.5v your maximum theoretical length would reduce as temperature increases. The CAT 5 standard however caters for temperature range of something like -55c to +60c whilst all else remains consistent including certified length. 

So in theory there would be an effect, in practice the range should be covered by the standard just make sure you are not trying to pump 10gb/s over cat6 copper at 90meters in 60c and you should be ok!

Regards
Shane

> On 4 Mar 2014, at 10:00 pm, Damian Guppy <the.damo at gmail.com> wrote:
> 
> From a laws of physics point of view it makes sense. As temperature of
> a conductor increases so does its resistance. As to what effect that
> translates into in the real world with regards to network cabeling im
> not to sure.
> 
> --Damian
> 
> Sent from my Windows Phone From: Paul Gear
> Sent: 4/03/2014 6:53 PM
> To: ausnog at lists.ausnog.net
> Subject: [AusNOG] Cable length limits?
> Hi all,
> 
> I'm working on a project involving a new facility being built in
> Townsville.  A consultant on the project mentioned to me today that he
> had heard some discussions which suggested that the maximum distance of
> 90m on a Cat5e/Cat6 run applies to environments where the ambient
> temperature is around 20 degrees, and that higher temperatures can
> actually require lower length limits.
> 
> Can anyone confirm or deny, and/or point to some relevant references?
> Google seems to have some relevant hits, but discerning the wheat from
> the chaff is tricky - many of the first few hits for the searches I did
> were from companies trying to sell higher grade cabling.
> 
> Thanks in advance,
> Paul
> 
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