Abstract: Digital balanced cable，which is widely utilized in Generic Cabling System (GCS)，is the primary transmission medium. However，the universal standards and test methods are based on 90 m baseline model，and in factory the digital balanced cable is generally produced in 1 000 ft (305 m) per case，for the convenience of performance monitor and quality control on cable products，test method on 305 m long cables is an urgent need. This paper has proposed a test method of return-loss and near-end cross-talk on 305 m long cables，it mainly utilizes vector network analyzer (VNA) and impedance converter to cover the measurements of all-pairs on near-end performance testing. We also make comparison and analysis according to 90 m Channel model in TIA IEC. It proves that we can preliminarily estimate the transmission quality of the communication cables through test results of return-loss and near-end cross-talk in 305 m long cables.

Key words:  Industrial long cables, Near-end cross-talk, Return-loss, 305 m, 1 000 ft