CAT-5 Cables

UffDa

UffDa

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Sep 11, 1999
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This may be a silly question, but do Cat-5 cables go bad? The short cable that came with my modem doesn't work. I checked it for continuity, and it's fine. No resistance or broken wires. I have other cables that seem to be intermittent. Strange. :confused:
 
Did you look at the pins in the network jack that the Cat-5 plugs into?

We've had pins fail on working switches.
 
coule be tarnish - just enough that the tester gets good signal but the modem doesn't.
could also be bad connector in the modem as suggested above.
 
The biggest problem I've seen, those clips break off and so the cable doesn't stay fully inserted into the plugs.
 
I took a close look at all the contacts. They are all gold plated and look fine. The short cable that came with the cable modem just does not work no matter what I do with it.
I played around with another cable and my old wireless router is now working.
 
They certainly can seem fine to a common DC ohmmeter or continuity tester or a cheap cable tester and have problems and yet have problems at 25MHz which is where 100BASE-T works. Furthermore, to "work" at 25MHz, the cable really needs to work up to at least about 250MHz to really get the waveshape right. The waveshape thing is where the transmitter and receiver come in and why a cable may work when connecting device X to router Y but won't work when connecting device W to switch Z; just cut that cable in half and toss it out because a flakey cable can make your life miserable and replacing it costs like five bucks. And that's the bottom line: if in doubt, toss it out.

Most of these CAT-5 cables are cheap things made in Chinese sweatshops. They don't work well. They fall apart. The only reason they work at all is that the folks at Marvell and Broadcomm have done an amazing job of making the PHYs, the transmitters and receivers, that are so sophisticated that they can all but work with two tin cans and a string.
 
As mentioned above, a simple continuity test is a reasonable first step. However, that won't tell you whether it has good "RF" performance characteristics or not. Bad contacts at connection points can provide a good continuity but, fail with RF.

The cables I have received with my wireless routers, while serviceable, were inferior quality and not worth the trouble. Go to STAPLES, OFFICE DEPOT, etc. and spend a few dollars to buy a good "heavy" Ethernet cable and don't worry about fixing a 50 cent cable.
 
UffDa said:
This may be a silly question, but do Cat-5 cables go bad? The short cable that came with my modem doesn't work. I checked it for continuity, and it's fine. No resistance or broken wires. I have other cables that seem to be intermittent. Strange. :confused:
Click to expand...
Yes they can and do go bad, usually within the RJ45 connector. If you still need some, shoot me a PM and I can ship you a few in whatever sizes you need.
 
Joshua J. said:
Get a roll of Cat 5 cable and a plug kit, it's nice to have new cables on demand.
Click to expand...


A good suggestion. It's inexpensive and very handy.

Keep in mind that CAT5 bulk cordage (a cable is an assembly with connectors on it; without connectors, what you have is "cordage") comes in two major varieties, stranded and solid. Solid is for permanent installation not subject to repeated flexing. Stranded is more flexible and pliable and suitable for room drops (the cable that connects from a wall jack to a piece of equipment such as a PC) and patch cables.

The RJ-45 plugs used on Stranded and Solid are subtly -- but significantly -- different. Some time ago, I solved a problem at my workplace with flakey patch cables by discovering that they were putting RJ-45 plugs designed for solid wire onto stranded cordage. In most larger IT operations, you should find two bins of RJ-45 plugs kept well-separated and well-labeled, one for solid cordage used for installation and a second for use on stranded cordage used on patch cables.

If you have a big problem with breaking patch cables, there is a variant called Industrial Ethernet which uses ruggedized cables. They're expensive, but they can be economically justified in many cases.
 
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