frequency bottom profiler sonar, one SQS-503 hull mounted active search sonar, one SQS-502 high frequency mortar control sonar and one SQS-11 hull mounted active search sonar. DELEX refit The DEstroyer Life EXtension (DELEX) refit was born out of the need to extend the life of the steam-powered destroyer escorts of the Canadian Navy in the 1980s until the next generation of surface ship was built. Encompassing all the classes based on the initial St. Laurent (the remaining St. Laurent, Restigouche, Mackenzie, and vessels), the DELEX upgrades were meant to improve their ability to combat modern Soviet submarines, and to allow them to continue to operate as part of NATO task forces. The DELEX refit for the Mackenzie class was the same for the Improved Restigouche-class vessels. This meant that the ships would receive the new tactical data system ADLIPS, new radars, new fire control and satellite navigation. They exchanged the SQS-503 sonar for the newer SQS-505 model. They also received a triple mount for torpedo tubes that would use the new Mk 46 homing torpedo. The Mark 46 torpedo had a range of at over with a high-explosive warhead weighing . Construction and career Yukon was ordered in 1957 and laid down on 25 October 1959 at Burrard Dry Dock Ltd., North Vancouver. She was launched on 27 July 1961 and commissioned into the RCN on 25 May 1963 with the classification number DDE 263. Though built on the west coast, Yukon immediately transferred to the east coast, sailing for Halifax, Nova Scotia on 27 July. She remained on the east coast for a year, where as part of the First Canadian Escort Squadron, Yukon escorted Queen Elizabeth II aboard on visits to several Canadian port cities. She returned to the Pacific in 1965. She was largely used as a training ship following her transfer by the RCN and later in the CF under Maritime Forces Pacific. In 1970, Yukon sailed with sister ship and the auxiliary vessel on a training deployment throughout the Pacific, working with several navies and visiting Japan. In February 1975 underwent a mid-life refit. Upon completion, the ship joined Training Group Pacific. On 17 January 1983, Yukon collided with the U.S. aircraft carrier , with Yukon reporting slight damage to her mast. She underwent the DELEX refit at the Burrard Yarrow shipyard at Esquimalt, British Columbia from 28 May 1984 to 16 January 1985. In