Sirius Satellite Radio said Wednesday that its losses narrowed and revenue jumped as subscribers flocked to its service.Sirius’ net loss shrank to $163 million from $180 million on revenue that about doubled to $167 million. During the quarter, Sirius added about 441,000 net subscribers for a total of 5.1 million. The cost of acquiring each customer decreased 23% to $114 from $149 on lower average subsidy rates as the company continued to reduce manufacturing and chip-set costs. The Gotham-based company also reiterated its forecast for 6.3 million users by year’s end. Both Sirius and larger rival XM Satellite Radio offer monthly subscriptions for $13 a month. XM reported upbeat quarterly earnings earlier this week.