MAC: maintenance of practical systems

National Transcommunications Ltd (NTL), one of the three successor bodies emerging from IBA UK, own and operate the United Kingdom Direct Broadcast Satellite Uplink. This uplink transmits five D-MAC services to two geostationary satellites situated at 31° West. The equipment at the DBS Uplink is maintained by a mobile maintenance team based in Southampton which is also responsible for the maintenance of approximately seventy television and radio transmitters. The concepts used in the design of the DBS Uplink are based on more than thirty years experience in the construction, operation and maintenance of broadcast transmission systems. The authors describe the equipment installed at the uplink, then discuss the choice of test equipment and give examples of the measurements made