cable length FREE cabling and networking Helpdesk
 Question by Charles Jansen posted 29 Oct 2000
 cable length
In my plant we have run a Cat-5 cable fromthe computer room to our plant manager's office. This office will house a switch to support a number of terminals. The cable length is 345 ft. I understand this should be ok for T-Base 10, but I would like to know if there are going to be issues. Should I split this line with a repeater at it's midpoint or will it be ok to leave as is?
 Answer by Dmitri Abaimov posted 30 Oct 2000
Dear Charles,

The standards-based cabling channel would be 327 feet including the cable itself plus cords. You have slightly more. However, I don't see problems with 10BASE-T operation over 345 ft.

There is one caveat, though. The biggest concern would be to ensure that your link is done perfectly, without any deviation from CAT5 installation rules. The rules control crosstalk between pairs, and that's important since you have more attenuation with the length that’s over the limit. Thus attenuation-to-crosstalk ratio (ACR parameter) gets lower. It may cause excessive bit errors.

So please take a look at your link. It should be clear of pair untwisting in the termination points. The cable should not be kinked or jammed or otherwise damaged. The cabling pathway should be far enough from potential EMI sources like power cables. In most cases 1 foot is enough.

Again, if the installation is done well, I don't see any potential problem with 10BASE-T.

Dmitri Abaimov, RCDD

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