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How do you filter out noise on a network

Posted on 2004-11-19
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Last Modified: 2013-04-08
Hi
We have installed a small LAN which contains 4 pc & 8 port switch box , we are having problems with the network and suspect there is noise on the line's ,How do you filter a cat5 cable
regards turlough
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Question by:visualbasic
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by:muhalok
ID: 12628293
Why do you suspect that there is a noise on the line? What are the symptoms?
Also: what do you mean filter? (For physical noise - try using screened cable (I am not sure whether CAT5 is screened from static electricity and magnectic fields).
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by:lawson2305
ID: 12628337
Use Shielded cable if you are concerned with outside interference.
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by:muhalok
ID: 12628638
Yeah, "shielded" I meant, not "screened" - poor translation from Hebrew. :)
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by:PennGwyn
ID: 12631443
Shielded and screened both exist, and are different from each other.  Normal Cat5 is neither.  Cat5 Screened has metal around the outside of the connector (which connects to screen around the pairs running the length of the cable) -- it doesn't achieve much unless you have a way to ground this.
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muhalok earned 200 total points
ID: 12632222
PennGwyn - thanks for opening my eyes!
For the cause of clarity I am posting the following:

From:  http://www.techfest.com/networking/lan/ethernet5.htm

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5.0 Ethernet Cabling and Connectors
5.1 Twisted Pair Cabling
Twisted pair cables are so named because pairs of wires are twisted around one another. Each pair consists of two insulated copper wires twisted together. The wire pairs are twisted because it helps reduce crosstalk and noise susceptibility. High quality twisted pair cables have about 1 to 3 twists per inch. For best results, the twist rate should vary significantly between pairs in a cable.

Twisted pair cables are used with the following Ethernet physical layers: 10Base-T, 100Base-TX, 100Base-T2, 100Base-T4, and 1000Base-T. The following sections describe the various types of twisted pair cabling.

5.1.1 Unshielded Twisted Pair Cabling (UTP)
As the name implies, "unshielded twisted pair" (UTP) cabling is twisted pair cabling that contains no shielding. For networking applications, the term UTP generally refers to the 100 ohm, Category 3, 4, & 5 cables specified in the TIA/EIA 568-A standard. Category 5e, 6, & 7 standards have also been proposed to support higher speed transmission. UTP cabling most commonly includes 4 pairs of wires enclosed in a common sheath. 10Base-T, 100Base-TX, and 100Base-T2 use only 2 of the twisted pairs, while 100Base-T4 and 1000Base-T require all 4 twisted pairs.

UTP Cable Illustration  
 


The following is a summary of the UTP cable Categories:


Category 1 & Category 2 - Not suitable for use with Ethernet.
Category 3 - Unshielded twisted pair with 100 ohm impedance and electrical characteristics supporting transmission at frequencies up to 16 MHz. Defined by the TIA/EIA 568-A specification. May be used with 10Base-T, 100Base-T4, and 100Base-T2.
Category 4 - Unshielded twisted pair with 100 ohm impedance and electrical characteristics supporting transmission at frequencies up to 20 MHz. Defined by the TIA/EIA 568-A specification. May be used with 10Base-T, 100Base-T4, and 100Base-T2.
Category 5 - Unshielded twisted pair with 100 ohm impedance and electrical characteristics supporting transmission at frequencies up to 100 MHz. Defined by the TIA/EIA 568-A specification. May be used with 10Base-T, 100Base-T4, 100Base-T2, and 100Base-TX. May support 1000Base-T, but cable should be tested to make sure it meets 100Base-T specifications.
Category 5e - Category 5e (or "Enhanced Cat 5") is a new standard that will specify transmission performance that exceeds Cat 5. Like Cat 5, it consists of unshielded twisted pair with 100 ohm impedance and electrical characteristics supporting transmission at frequencies up to 100 MHz. However, it has improved specifications for NEXT (Near End Cross Talk), PSELFEXT (Power Sum Equal Level Far End Cross Talk), and Attenuation. To be defined in an update to the TIA/EIA 568-A standard. Targetted for 1000Base-T, but also supports 10Base-T, 100Base-T4, 100Base-T2, and 100BaseTX.
Category 6 - Category 6 is a proposed standard that aims to support transmission at frequencies up to 250 MHz over 100 ohm twisted pair.
Category 7 - Category 7 is a proposed standard that aims to support transmission at frequencies up to 600 MHz over 100 ohm twisted pair.
5.1.2 Screened Twisted Pair (ScTP)
Screened Twisted Pair (ScTP) is 4-pair 100 ohm UTP, with a single foil or braided screen surrounding all four pairs in order to minimize EMI radiation and susceptibility to outside noise. Screened twisted pair is also called Foil Twisted Pair (FTP), or Screened UTP (sUTP). ScTP can be thought of as a shielded version of the Category 3, 4, & 5 UTP cables. It may be used in Ethernet applications in the same manner as the equivalent Category of UTP cabling.
ScTP Cable Illustration  

 

5.1.3 Shielded Twisted Pair Cabling (STP)
Although screened twisted pair (ScTP) is technically a form of shielded twisted pair, the term "shielded twisted pair" (STP) most often refers to the 150 ohm twisted pair cabling defined by the IBM Cabling System specifications for use with Token-Ring networks. The twisted pairs in 150 ohm STP are individually wrapped in a foil shield and enclosed in an overall outer braided wire shield. The shielding is designed to minimize EMI radiation and susceptibility to crosstalk. 150 ohm STP is not generally intended for use with Ethernet. However, the Ethernet standard does describe how it can be adapted for use with 10Base-T, 100Base-TX, and 100Base-T2 Ethernet by installing special impedance matching transformers, or "baluns", that convert the 100 ohm impedance of the Ethernet transceivers to the 150 ohm impedance of the STP cable. These baluns are available from companies such as AMP, IBM, and Cambridge Connectors.

The various versions of 150 ohm STP cable are identified by a "Type" number. The original IBM Cabling System 0specifications defined STP cable Types 1, 2, 6, 8, & 9 for support of Token-Ring frequencies up to 16 MHz. Later, an enhanced IBM Cabling System defined STP-A cable Types 1A, 2A, 6A, & 9A for support of FDDI frequencies up to 100 MHz. The "A" suffix denotes the enhanced IBM Cabling System. Type 1 is the heavy black cable that is most commonly associated with the IBM Cabling System. It contains only 2 twisted pairs as compared to UTP and ScTP which typically contain 4 twisted pairs. Note that 100Base-T4 and 1000Base-T cannot be adapted to use STP because they require a cable with 4 twisted pairs.

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by:myron-szy
ID: 12636354
turlough, describe the problems you're having with the network.  There are way too many things that can stop a network from performin as it should.  The better quality information you can post about the problems suffered on your network. the better chance someone will be able top help you.  Your question does not make sense.

In the meanwhile, are there any transmitters close by?

Think is, with cat5e cable that's wired correctly, the tranmit pair and receive pair are twisted.  One wire carries the data.  The other is a mirror image of the other.  For one that helps cancel noice on the wire and second is that the electronics can tell if the signal has been corrupted.  I assume this would cause the hardware in the network adapters to re-transmit.  It not that, at least signal an error to the operating system that's sending to the OS can re-transmit data.

This could be a software problem?  The switch could be faulty?  Etc....

We need a batter description of the problem.
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