--Barbara E. Thompson
If you`re having trouble finding Category 5 plenum-rated cable--and who isn`t?--Mohawk/CDT (Leominster, MA) may have a product to fit your installation needs. Its LAN 75 unshielded twisted-pair cable has been tested for Category 5 plenum applications with link distance limits of 75 meters, and its LAN 100 cable for longer runs.
Although these modified plenum cables do not meet the 100-meter requirement for premises wiring as stated in the EIA/TIA-568 standard, "with the current Category 5 plenum cable shortage," says Russ Oliver, RCDD, vice president of technical services at Comlink Inc. (Marlborough, MA), "this is a great alternative for installations that are within 75 meters."
The cables have the same basic design as plenum-rated Category 5 UTP but use a modified fluoropolymer (see February 1995, page 55). "This insulation is a well-established plenum material," says Jim Baker, Mohawk`s vice president for engineering, "except that it cannot meet the attenuation requirements for the 100-meter [EIA/TIA-568] standard. It meets all the other parameters--impedance, crosstalk, structural return loss. However, in the high-frequency area," Baker adds, "it does not meet the attenuation budget over the full 100 meters.
"We`re shipping the product for limited applications because we want to ensure that the customer installing the product understands the distance restriction. It`s not a long-term solution. We found out that where people understand the installation`s requirements and do not have 100-meter runs, this product will meet the criteria for the EIA-568 standard," he adds.