you will have a strong ADSL signal and not one that has travelled several miles over cable designed for up to 4 KHz audio maximum frequency.
Cat 5e v's Cat 6?
- Thread starter Greenie9657
- Start date
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jabuzzard
If you read the BT Suppliers Information Note 351
http://www.sinet.bt.com/351v4p5.pdf
paragraph 3.4.2 you will see the charactoristic impedance of the subscriber loop from the exchange is nominally 300 ohms. In practice cable variations can result in the impedance being somewhere between 300 and 1000 ohms.
Most often it was around 600 ohms
On long lines loading coils were fitted to compensate for the capacitive loading of the line. The capacitive loading takes the charactoristic impedance too far from nominal. As loading coils will reduce ADSL signals they have to be removed on long lines carrying ADSL. Removing the coils means the charactoristic impedance of the line goes even further from the nominal. Removing the coils also reduces the quality of speech on the line.
When you compare the charactoristic impedance of the line to the charactoristic impedance of Cat5 / Cat6 at ADSL frequencies you will find a significant difference.
Read http://en.wikipedia.org/wiki/Signal_reflection ( save me typing it out ) and draw you own conclusion as to whether an impedance mismatch has no effect on the ADSL signal.
If you read the BT Suppliers Information Note 351
http://www.sinet.bt.com/351v4p5.pdf
paragraph 3.4.2 you will see the charactoristic impedance of the subscriber loop from the exchange is nominally 300 ohms. In practice cable variations can result in the impedance being somewhere between 300 and 1000 ohms.
Most often it was around 600 ohms
On long lines loading coils were fitted to compensate for the capacitive loading of the line. The capacitive loading takes the charactoristic impedance too far from nominal. As loading coils will reduce ADSL signals they have to be removed on long lines carrying ADSL. Removing the coils means the charactoristic impedance of the line goes even further from the nominal. Removing the coils also reduces the quality of speech on the line.
When you compare the charactoristic impedance of the line to the charactoristic impedance of Cat5 / Cat6 at ADSL frequencies you will find a significant difference.
Read http://en.wikipedia.org/wiki/Signal_reflection ( save me typing it out ) and draw you own conclusion as to whether an impedance mismatch has no effect on the ADSL signal.
Which misses the point that an FTTC extension provided by BT will be done in Cat5e. Why would BT use more expensive cable if a length of cheaper CW1308 would give a better result?
You friend replaced a length of Cat5e with CW1308 and got an improvement. Did they first check the Cat5e was properly and cleanly terminated? Did they also check the Cat5e was not in any way damaged or minimum bend radius exceeded?
Finally the kicker to the nonsense impedance change is that Cat5e has a nominal impedance of 100Ω and CW1308 of 97.8Ω. As you freely admit the line from the exchange will be all over the place depending on a host of factors. The difference between the impedance of the Cat5e and the CW1308 is of no importance. What does make a difference is the much reduced crosstalk etc. of the Cat5e/6 cable in the much more hostile environment of a home where the amount of electromagnetic interference is much higher than outside in the street.
I can see that you have been spouting this rubbish for a while but you are basically dead wrong.
You friend replaced a length of Cat5e with CW1308 and got an improvement. Did they first check the Cat5e was properly and cleanly terminated? Did they also check the Cat5e was not in any way damaged or minimum bend radius exceeded?
Finally the kicker to the nonsense impedance change is that Cat5e has a nominal impedance of 100Ω and CW1308 of 97.8Ω. As you freely admit the line from the exchange will be all over the place depending on a host of factors. The difference between the impedance of the Cat5e and the CW1308 is of no importance. What does make a difference is the much reduced crosstalk etc. of the Cat5e/6 cable in the much more hostile environment of a home where the amount of electromagnetic interference is much higher than outside in the street.
I can see that you have been spouting this rubbish for a while but you are basically dead wrong.
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How long is the twisted pair in a typical FTTC install ? Do you have real experience of a typical rural telephone line bringing ADSL service to a house several miles from the local exchange. ?
If there is more than one ADSL signal then cross talk between pairs might be a problem. Cross talk between an audio signal pair and the ADSL pair is not a problem as they arrive on the same pair to the building. So the reduced cross talk in Cat 5 or 6 is a red herring in a domestic situation.
I'm curious as to where you got the latter figure from.
Give it a rest, bernard, you clearly don't have a clear picture of what you're talking about.
Easy, Googled for a CW1308 data sheet. The idea that more twists of Cat5e would change the impedance is plain silly anyway. What does he think happens when you mix Cat5e, Cat6 and Cat6a when carrying 1Gbps Ethernet, all falls apart or something.
He is claiming that in some specific instances it makes a difference, and experiment always trumps theory. However extraordinary claims require extraordinary evidence and I remain with good reason sceptical that the change from Cat5 to CW1308 was the reason for the improved speed. We just don't know enough about the testing to make that conclusion.
I will add throw in another spanner into the impedance claim, the cable from a wall socket to an ADSL modem is generally not CW1308 specification cable either...
Please link me to the specific datasheet you found.
97.8 ohms is the resistance end to end of 1 km of cable. Nothing to do with the charactoristic impedance which depends on inter conductor capacity, inductance and frequency of signal. These values are per unit length.
The actual length of the cable does not affect the charactoristic impedance so the value 97.8 ohms does not come into the equation unless the unit length chosen for the other values is 1 km.
The actual length of the cable does not affect the charactoristic impedance so the value 97.8 ohms does not come into the equation unless the unit length chosen for the other values is 1 km.
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