Cat 5 only uses 4 out of the 8 wires in the cable. You'd need to do a continuity and isolation test on each individual wire in the cable and hopefully you'd come up with 4 good wires out of the 8. Make sure the 4 wires you choose have continuity from one end to the other and no continuity with another wire in the bundle. If you have to mix & match colors to get 2 good pairs- you may lose some network speed, but I'd give it a try.
OT - Cat 5 wireing
When I built my house two years ago, I ran cat 5e wire behind all the walls I could ever imagine I would want a network plug. After the first two most remote locations, someone was good enough to tell me "Ya know, your not supposed to staple it up tight like that". In hindsight, I should have re-done those two locations, but I was hung over from my bachelor party the night before.
Now, two years later, I want to move my office into that room. Sure enough, neither of the two cable runs are good. Although both show continuity throughout all 8 wires, one gives me no network connection and the other reads limited connectivity yet never finds the network.
They are both stapled up tight, going around a couple of corners, so using either to pull a new line is out of the question. Is there anything I can do to possibly combine the two to try to get a single connection, or anything that might clean up the signal since I have continuity. Short of that, looks like I'll be running a new line down a different wall into the crawl space.
Now, two years later, I want to move my office into that room. Sure enough, neither of the two cable runs are good. Although both show continuity throughout all 8 wires, one gives me no network connection and the other reads limited connectivity yet never finds the network.
They are both stapled up tight, going around a couple of corners, so using either to pull a new line is out of the question. Is there anything I can do to possibly combine the two to try to get a single connection, or anything that might clean up the signal since I have continuity. Short of that, looks like I'll be running a new line down a different wall into the crawl space.
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That's just it. I have continuity and isolation on all wires. Just not registering a network. I thought if the staple had crushed a twisted pair so that it was no longer twisted, this could be an issue. Not real clear on how cat5 really works since I'm used to standard low voltage wire. If I have continuity and isolation, I'm good to go.
The jacks are wired improperly. The proper twisted pairs have to be on the right pins. They make cheap testers you could check this with. Otherwise, you'll have to pull the jacks out and check them.
The suggestion was made here that you find four good wires. In fact you need to find two good pairs. E.g., blue/white MUST be paired with white/blue etc. in order to get connectivity. But if (at both ends of the cable) you substitute brown/white and white/brown where blue/white and white/blue should go, because blue/white&white/blue were NG -- that's OK, too.
But do check the wiring of the connectors per adone36's suggestion, and do get a tester. I have one that comes in two parts. One part is "passive" and serves to terminate the pairs at one end of the cable; the other is active and has the circuitry, batteries and LEDs that look for shorts and opens, proper pairing, and proper termination of the cable. Flashing LEDs indicate problems. Costs a few bucks at your local electronics store, but cheaper than hair restoral (after you've torn yours out).
Now, if I could only remember (without consulting documentation) which four pins (i.e., two pair) on the RJ-45 connector are actually used for Ethernet, and which are not...
But do check the wiring of the connectors per adone36's suggestion, and do get a tester. I have one that comes in two parts. One part is "passive" and serves to terminate the pairs at one end of the cable; the other is active and has the circuitry, batteries and LEDs that look for shorts and opens, proper pairing, and proper termination of the cable. Flashing LEDs indicate problems. Costs a few bucks at your local electronics store, but cheaper than hair restoral (after you've torn yours out).
Now, if I could only remember (without consulting documentation) which four pins (i.e., two pair) on the RJ-45 connector are actually used for Ethernet, and which are not...
In a "standard" ethernet configuration the Orange and Green sets are the pairs used. Those are on pins 1, 2, 3, and 6.
At 0Hz (DC)...but what is the impedance (series and parallel) at 300MHz?
The twisted pairs in Cat5 form a transmission line, the impedance of this is affected by crushing, or tightly bending the cable.
Quote:
I have continuity and isolation on all wires.
At 0Hz (DC)...but what is the impedance (series and parallel) at 300MHz?
The twisted pairs in Cat5 form a transmission line, the impedance of this is affected by crushing, or tightly bending the cable.
The likely cause of the problem is a staple through the casing somewhere or a crimp that has compromised the resistance between two of the wires (seeing you haven't ran the wire 1000ft or something stupid like that). You DO NOT necessarily need to use the color pairs as suggested as long as the pin-out is correct and the wires are good. If you're running 100Mbit, you'll probably be ok because the specs on TP cable is much higher than what it's used for. Electrically speaking, yes, you are better off using the color pairs, but it may not be necessary depending on the situation and environment. In a business I'd never do this, but at my home, as long as it works I don't care. Just make sure you have pins 1,2,3, and 6 matched up end to end. You might try using the brown and blue pairs instead of orange and green. If those two pairs work, you should be fine.
Then why didn't the multimeter test show this?
Quote:
The likely cause of the problem is a staple through the casing somewhere or a crimp that has compromised the resistance between two of the wires
Then why didn't the multimeter test show this?
It would. You most likely problem as I stated above is that the wires have continuity, but they are not connected so as to provide 2 proper twisted pairs. Buy/borrow the LAN tester.
I would go so far as to say it "should" not that it would. But, adone36 is right, always check the basics and check the pinouts. When you're talking wire and resistance and impedance we're in the analog world and not the digital world so nothing is certain when it comes to what could be causing the problem and meters don't always reveal what they should. It could also be a bad jack or just a bad punch on one end. I'm also assuming the wire is terminated on a jack on each end and doesn't have the RJ45 directly crimped on. If it has jacks on each end, I'm also assuming they were punched properly with a punch tool and not with a screwdriver or something.
Hope this helps.
Quote:
Originally Posted by adone36 /forum/post/0
It would. You most likely problem as I stated above is that the wires have continuity, but they are not connected so as to provide 2 proper twisted pairs. Buy/borrow the LAN tester.
I would go so far as to say it "should" not that it would. But, adone36 is right, always check the basics and check the pinouts. When you're talking wire and resistance and impedance we're in the analog world and not the digital world so nothing is certain when it comes to what could be causing the problem and meters don't always reveal what they should. It could also be a bad jack or just a bad punch on one end. I'm also assuming the wire is terminated on a jack on each end and doesn't have the RJ45 directly crimped on. If it has jacks on each end, I'm also assuming they were punched properly with a punch tool and not with a screwdriver or something.
Hope this helps.
Definitely borrow a tester and hunt for any good pairs. Choose the best two pair, wire it up.
Then on the desktop side set the speed to 100mbps fixed instead of auto negotiate. In weak signal conditions some NIC's will try and negotiate a proper speed and never get a connection as a result.
Then on the desktop side set the speed to 100mbps fixed instead of auto negotiate. In weak signal conditions some NIC's will try and negotiate a proper speed and never get a connection as a result.
Oh Boy..characteristic impedance is very important to high frequency signals, weather they're digital or analog.
A wire that is continuous at DC, may not be at 300 MHz...this is a function of impedance, which is greatly affected by cable geometry...a crushed, or tightly bent cable will exhibet electrical reflections at this point...an impedance mismatch.
Obviously, he's measuring resistance, not impedance.
Quote:
When you're talking wire and resistance and impedance we're in the analog world and not the digital world
Oh Boy..characteristic impedance is very important to high frequency signals, weather they're digital or analog.
A wire that is continuous at DC, may not be at 300 MHz...this is a function of impedance, which is greatly affected by cable geometry...a crushed, or tightly bent cable will exhibet electrical reflections at this point...an impedance mismatch.
Quote:
meters don't always reveal what they should.
Obviously, he's measuring resistance, not impedance.
I'm guessing in all of this simple wireless is out?
FWIW, Twisted pair is engineered such that any interference will introduce the same signal on both of the wires of a given twisted pair. because an inverted signal is sent down the second wire, when it's inverted again, and mixed with the other signal, the interference is naturally cancelled out.
Just like a balanced audio line....invented over 100 years ago.
I have stapled, bent, and abused ethernet wire and it always seems to work.
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