White Paper/ Standards Seite 1 / 5

White Paper

02. Juli 2002

Andreas ClauserHauptsitzBinzstrasse 31CH-8622 WetzikonTel +41 1 933 8375Fax +41 1 930 49 41Internet www.rdm.com

Do you know if your Cat. 6 patch cord has been tested according to standards?

Unfortunately, reality shows that many of the alleged Cat. 6

patch cords do not fulfil the values laid down in standards!

It is common knowledge that today most of the installations

are only measured as permanent links. But will your

installations still yield the required performance, once

the patch cords are connected? Is it enough when the

stranded cable complies with the standard? How can you

make sure yours is a good patch cord?

This article will give you the answers to all these important

questions when choosing patch cords. It also presents today’s

standards of patch cords and stranded cables and discusses

their differences. Furthermore, it clearly describes how to

proceedin order to find guaranteed top-grade patch cords.

Summary

Cat. 6 patch cords are specified in the standards PrEN 50173, ISO/IEC 11801 2nd Edition and

ANSI/TIA/EIA-568-B.2.1. They include defined minimum values for near-end crosstalk and return

loss.

Due to its consistent organisation the TIA/EIA-568-B.2.1, Draft 9 should be used as reference for the

assessment of flex cables and patch cords. The draft of ISO/IEC 11801 2nd Edition from April 2001

contains mistakes and should not serve as reference in the assessment of flex cables. CENELEC

with PrEN 50173 has not yet defined a required near-end crosstalk value for Cat. 6 patch cords.

There is only one way to make absolutely sure that your patch cord fulfils the standard, namely to ask

the manufacturer for the test record from patch cord production.

Detailed specifications

The Cat. 6 patch cords are specified in the standards PrEN 50173, ISO/IEC 11801 2nd Edition and

ANSI/TIA/EIA-568-B.2.1. These standards issue identical required values for return loss. ISO/IEC

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and TIA/EIA issue the same required values for near-end crosstalk, whereas CENELEC has not yet

determined values required for Cat. 6 patch cord near-end crosstalk (as of April 2002).

The new cabling standards specify patch cords of up to 20 metres. The frequency range is specified

from 1 to 250 MHz. The near-end crosstalk values vary depending on the patch cord's length. By

contrast the return loss values were specified independent of the patch cord's length.

.

Table 1: Standards for patch cords and flexible cables

Document Name Title

ANSI/TIA/EIA-568-B.2.1 Addendum No. 1 to TIA/EIA-568-B.2, "Transmission

Performance Specifications for 4-Pair 100 Category 6

Cabling", November 2001 Draft 10 Preliminary

ISO/IEC 11801 2nd edition 2nd CD, IT-Cabling for customer premises, April 2001

PrEN 50173 Information technology-generic cabling systems,

August 2001

The standards give identical values for flex cables. There is, however, a small but significant

difference: ISO/IEC 11801 specifies return loss between 4 and 250 MHz whereas ANSI/TIA/EIA set

their frequency range at between 1 and 250 MHz.

In reality, the return loss as specified in ISO/IEC 11801 2nd leads to the situation where the cable

fulfils the standard for a flexible cable of 100 m, but the patch cords of between 5 and 10 m no longer

fulfil the standard.

RL S-STP flex cable 100m a

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

1 10 100

Frequency [MHz]

Mag

nit

ud

e [d

B]

Limit C6 flex cable 1,2 100m side a 3,6 100m side a 4,5 100m side a 7,8 100m side a

RL S-STP flex cable 5m

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

1 10 100

Frequency [MHz]

Mag

nit

ud

e [d

B]

Limite C6 Cord 1,2 5m 3,6 5m 4,5 5m 7,8 5m Limit C6 flex cable

Graph 1 Graph 2

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Graph 1 shows the measurement of a 100 m flexible cable, which fulfils the specifications according

to ISO/IEC. It only falls short of the limit below 4 MHz. Then, 20 metres of the cable were cut off and

it was tested for the patch cords' limits as specified by ISO/IEC. To exclude any influence from the

connector and the connector's termination the cable was measured separately. The result is shown

below, in Graph 3: the patch cord fails. It is the same with patch cords of 10 metres (Graph 4). The

patch cords of 5 metres only just about fulfil the ISO/IEC requirements again (Graph 2).

The results are summarised in Table 2. They show that up to 3.7 dB of reserve can be lost from a

flexible cable to a patch cord of 20 metres due to the fact that ISO/IEC only start measuring cables

from 4 MHz upward.

Table 2: ISO/IEC 11801 2nd Edition

Standard for 100 m flex cable Standard for patch cord up to 20 m

Frequency range 4 ... 250 MHz 1 ... 250 MHz

Length 100 m 20 m 10 m 5 m

Frequency of

smallest reserve

1.4 dB

4.6 MHz

-2.3 dB

2.0 MHz

-1.4 dB

4.4 MHz

0.15 dB

8.9 MHz

Result PASS FAIL FAIL PASS

Conclusion: The draft of ISO/IEC 11801 2nd Edition from April 2001 contains mistakes and

should not serve as reference in the assessment of flex cables.

Graph 3 Graph 4

RL S-STP flex cable 20m

0.0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

1 10 100

Frequency [MHz]

Mag

nitu

de

[MH

z]

Limite Cord 1,2 20m 3,6 20m 4,5 20m 7,8 20m Limit (dB)

RL S-STP flex cable 10m

0.0

10.0

20.0

30.0

40.0

50.0

60.0

1 10 100

Frequency [MHz]

Mag

nitu

de [

dB]

Limite C6 Cord 1,2 10m 3,6 m 4,5 m 7,8 m Limit flex cable

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In a second step the measuring results were compared with the specifications of ANSI/TIA/EIA 568-

B2.-1 Draft 10 of November 2001. The results are summarised in Table 3.

Table 3: ANSI/TIA/EIA 568-B.2-1 Draft 10

Standard for 100 m flex cable Standard for patch cord up to 20 m

Frequency range 1 ... 250 MHz 1 ... 250 MHz

Length 100 m 20 m 10 m 5 m

Frequency of

smallest reserve

-2.0 dB

1.5 MHz

-2.3 dB

2.0 MHz

-1.4 dB

4.4

0.15 dB

8.9

Result FAIL FAIL FAIL PASS

In TIA/EIA 568-B.2-1 Draft 10 the return loss specifications for flex cables are consistent with the

limits for patch cords, both starting at 1 MHz. The reserves for the limits of a 100 m flex cable and of

a 20 m patch cord also match. Furthermore, it is shown that the frequency of the worst value with

reference to the limit is doubled when the patch cord's length is cut in half. This effect is caused by

standing waves in the cable.

Conclusion: Due to its consistent organisation the TIA/EIA-568-B.2.1, Draft 9 should be used

as reference for the assessment of flex cables and patch cords.

Reality has shown that only a few of the alleged Cat. 6 patch

cords actually fulfil the values stipulated by the standards.

How can you make absolutely sure that your patch cord

complies with the TIA/EIA or ISO/IEC standards?

It is only possible if the patch cord production is subject to a

test system. The parameters near-end crosstalk and return

loss must be fulfilled in compliance with ANSI/TIA/EIA-568-

B.2.1 (as of Draft 9) or ISO/IEC 11801 2nd Edition.

How can a customer make sure such a test system was not

only implemented by marketing but also in production? Here

the only way is to ask for the manufacturer's test record of the

patch cord production, which should list the measured values

and the standards applied.

Conclusion: Ask the manufacturer for the test record of

the patch cord production.

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