Ethernet LAN Problem: UTP only works at 10 MHz

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Subject Author Date
Problem: UTP only works at 10 MHz Claudio Bogado Pompa 07-27-07
Posted by Claudio Bogado Pompa on July 27, 2007, 8:02 pm
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Why a UTP cable will work at 10 MHz but will not work at 100 MHz?
The same four cables are used in both frequencies.
I have that problem with some cables.
Greetings from Paraguay.
Claudio Bogado Pompa.


Posted by Robert Redelmeier on July 27, 2007, 8:26 pm
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> Why a UTP cable will work at 10 MHz but will not work at
> 100 MHz? The same four cables are used in both frequencies.
> I have that problem with some cables. Greetings from Paraguay.

Which termination pattern did you use? T-568-A or T-568-B?
A split pair will sometimes work at 10 but almost always fail at 100.

-- Robert





Posted by Juan Monico on July 28, 2007, 8:30 pm
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Robert Redelmeier wrote:
>> Why a UTP cable will work at 10 MHz but will not work at
>> 100 MHz? The same four cables are used in both frequencies.
>> I have that problem with some cables. Greetings from Paraguay.
>
> Which termination pattern did you use? T-568-A or T-568-B?
> A split pair will sometimes work at 10 but almost always fail at 100.
>
> -- Robert
Why would A vs B make any difference? Neither one splits a pair.
Standard cross-over cables, for example, are simply wired to the
T-568-A spec on one end and the T-568-B on the other.

A more likely explanation is that he is running on old telephone plant
quad pair style cable which will work reasonably well for short and
medium length runs at 10Mbps but not at all at 100Mbps.

Cat5 cable, which is required for 100Mbps operation, has very specific
specs for the twist on each pair. The no. of twists per unit length is
different from pair to pair in order to minimize both near end and far
end cross-talk.
See: pp 278-280 ISO/IEC 8802-3: 1996(E), the ISO std. for 10Base10.

Posted by Carl Navarro on July 28, 2007, 9:44 pm
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wrote:

>Robert Redelmeier wrote:
>>> Why a UTP cable will work at 10 MHz but will not work at
>>> 100 MHz? The same four cables are used in both frequencies.
>>> I have that problem with some cables. Greetings from Paraguay.
>>
>> Which termination pattern did you use? T-568-A or T-568-B?
>> A split pair will sometimes work at 10 but almost always fail at 100.
>>
>> -- Robert
>Why would A vs B make any difference? Neither one splits a pair.
>Standard cross-over cables, for example, are simply wired to the
>T-568-A spec on one end and the T-568-B on the other.

It was probably a subtle suggestion that if the original poster could
answer the question, he would have wired it to one standard or the
other.

I'd like to believe that UTP means Category 5+ cable. Again, giving
the OP the benefit of the doubt.

I'm guessing split pair.

Carl Navarro



Posted by Robert Redelmeier on July 29, 2007, 1:02 pm
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>>Robert Redelmeier wrote:
>>>> Why a UTP cable will work at 10 MHz but will not work at
>>>> 100 MHz? The same four cables are used in both frequencies.
>>>> I have that problem with some cables. Greetings from Paraguay.
>>>
>>> Which termination pattern did you use? T-568-A or T-568-B?
>>> A split pair will sometimes work at 10 but almost always fail at 100.

>>Why would A vs B make any difference? Neither one splits a pair.
>>Standard cross-over cables, for example, are simply wired to the
>>T-568-A spec on one end and the T-568-B on the other.

> It was probably a subtle suggestion that if the original
> poster could answer the question, he would have wired it
> to one standard or the other.

Correct. Of course either will work, but if the OP
doesn't know about either, it is extremely likely the OP
split a pair. The correct patterns are non-intuitive.

> I'd like to believe that UTP means Category 5+ cable.
> Again, giving the OP the benefit of the doubt.

I read the same thing.

> I'm guessing split pair.

Likewise.

-- Robert




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