[AusNOG] Cable length limits?

[Tony]

On Tue, 04 Mar 2014 20:52:57 +1000, Paul Gear <ausnog at libertysys.com.au>  
wrote:

> 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.
>

He would be correct.


> Can anyone confirm or deny, and/or point to some relevant references?


TIA/EIA STANDARD TIA/EIA-568-B.2-1
Commercial Building Telecommunications Cabling Standard

http://www.net100ltd.us/Catalogs/TIA_EIA_Nov2008/tia-eia/TIA-EIA-568-B.2-1.pdf

(Annex G - p76)


> 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.
>


A quick google found me this doco:

http://www.belden.com/docs/upload/Temperature.pdf

Yes it's from a cabling company, but it references the relevant standard  
which does indeed say that you should "de-rate" the maximum cable length  
based on temperature.

The suggestion from the cabling manufacturers to use a higher grade  
cabling (with lower loss) is sound. Of course you could always just play  
it safe and base your cabling on shorter distances.


regards,
Tony.