• by Erik Sass  @eriksass1, July 7, 2010

Sirius XM Radio reported a record number of subscribers in the second quarter of 2010, when the satellite radio broadcaster added about 580,000 subscribers, compared to the second quarter of 2009, for a total 19.5 million.

The second-quarter results built on momentum established in the first quarter, when the satcaster added 185,000 subscribers, for a total of 755,000 net additions in the first half.

The proportion of trial subscriptions converting to full-time subscriptions (mostly through new car sales) rose from 44.3% in the second quarter of 2009 to 46.7% in the second quarter of 2010.

The 2010 results are a big improvement over fairly dismal numbers in 2008-2009, when worsening economic conditions hit Sirius XM's subscription base hard. Between the first half of 2008 and the first half of 2009, the company lost a total 590,000 subscribers, reflecting net losses of 404,000 and 186,000 in the first and second quarters, respectively.

On the basis of this strong performance, the company raised its year-end subscriber forecast to 1.1 million net subscription additions. That's more than double the first-quarter guidance of 500,000 net additions by year-end.

Sirius XM CEO Mel Karmazin remarked: "Our subscriber results mark the best quarter of gross additions, deactivations and net additions since the merger of Sirius and XM in July 2008." He added that improving numbers reflect "the attractiveness of satellite radio but maintains a cautious outlook for continued improvement in the economy."