Additional Cable And Lobe Length Recommendations; Maximum Attenuation; Signal To Next Ratio; Transmitter Variation - 3Com CoreBuilder 5000 User Manual

Additional Cable and Lobe Length Recommendations

All cable lengths are adjusted to provide adequate margin in real-time
configurations. The lengths also take into account the increased
tolerance to NEXT-related jitter.
The recommended lobe lengths consider any patch panels or
workstation attachment cables in the lobe. Ensure all cable in a
particular path is the same type (UTP or STP) to meet the cable
recommendations in this chapter.

Maximum Attenuation

To comply with the 802.5 standard, ensure that the channel does not
exceed a maximum attenuation of 19 dB in any configuration. The
channel is the transmission path from the medium interface connector
(MIC) of one transmitter to the MIC of the next receiver in line. 3Com
uses 19 dB as the maximum channel attenuation when computing
cable lengths.

Signal to NEXT Ratio

To reduce effective channel attenuation, maintain an adequate Signal to
Near-End Crosstalk (NEXT) Ratio (SNR).
Use the SNR to calculate recommended lobe lengths (both active and
passive) as suggested by the current IEEE 802.5 draft standards:
13.5 dB for STP links
12.0 dB for UTP links

Transmitter Variation

To calculate the recommended lengths, use transmitter variation as
suggested by the latest IEEE 802.5 draft standards:
3.5 dB for STP links
2.0 dB for UTP links
Selecting Appropriate Cable Lengths 2-5