Just two years ago, in an Irish Independent interview, CEO Rob Clarke revealed that Spirit Radio had a weekly listenership of 165,000 people. Not bad for a specialist station which only debuted in January 2011 – but the genial New Zealander, while “happy” thus far, felt there was room for improvement and expansion.

This week Spirit released fifth-anniversary figures, by Amarách Research, which are borderline astonishing. An avowedly Christian radio station, run on a shoestring budget, now draws 540,000 listeners a week.

To put that in context, Today FM and Newstalk, with their much-higher profile and raft of big-name presenters, reach 900,000 and 709,000 respectively – not a whole lot more. Rob Clarke joked this week: “The increase in listenership is amazing, I have to say. We’re as surprised as anybody!”

More surprisingly, it’s most popular with 25-to-34-year-olds. How did this happen?

This is a more-or-less post-Catholic society; religion is generally ignored at best and derided at worst, particularly by the young. Media – mainstream or social – with its often illiberal group think, is particularly hostile.

Spirit delivers a standard mix of talk, news and music, but there are radical differences. The talk is calm and reasoned with a spiritual bent; the news accentuates the positive far more than normal; the music is two-thirds comprised of a genre little-known in Ireland: Contemporary Christian.

The station doesn’t have that dayglo brashness one usually encounters on radio. The tone is gentle, easy-going, reflective.

By most metrics, Spirit should be a dismal failure – but those Amarách figures show the opposite. As Dr Robbie Smyth, deputy head of faculty in journalism and media communications at Griffith College, says: “Their success is unique. Most stations build an audience with competitions, big sponsors, big names; they haven’t done any of that.”

So how to explain Spirit’s against-the-odds triumph – divine intervention?

Well, not quite. First, as Robbie Smyth points out, Spirit’s set-up and operating costs are considerably lower than stations such as 98FM and Spin. According to Rob Clarke, a third of Spirit’s revenue comes from advertising, the rest from public donations: mostly small, regular contributions.

“We’re listener-supported,” he says. “A whole bunch of people help us pay the bills. They like what we’re doing and want to help. And it makes them feel this is their station.”

Having a multi-city licence is also significant. (Spirit broadcasts on FM in Dublin, Limerick, Cork, Galway, Waterford, Bray/Greystones, Dundalk and Naas/Newbridge, and nationwide on MW.) “Multi-city licences really do seem to work in a station getting established and building an audience,” Robbie Smyth says. “4FM is another example. Whereas Dublin-only is a tough market, there are just so many.

“It should also be said that Spirit have no direct competitors. They’ve found a niche, and I don’t think anyone else will try to tap it. The Irish market is too small.”

Daithi McMahon, an award-winning radio producer, notes that Spirit’s Twitter following has increased six-fold and Facebook Likes almost trebling over the last four years. He says: “I would argue that social media helps a station connect with and grow its audience.”

But there’s more to this story than prosaic stats and the mechanics of broadcasting. Clearly Spirit are tapping into something – addressing some need in the listening public.

“Irish people are still very spiritual,” Robbie Smyth says. “Spirit meets that need. There’s genuine interest in what they do.”

Importantly, while the station is self-evidently religious, it’s not off-putting or dogmatic. Indeed, our own firebrand atheist, Ian O’Doherty, often appears on Wendy Grace’s show for a “civil conversation”.

Rob Clarke points out that staff come from a wide range of Christian churches, and Spirit addresses issues of interest to everyone. “We’re not ideological, and like to believe we’re nudging people to think about the important conversations in life: with God, those around us, people in need,” he adds.

“People find something here that’s speaking to them. They often tell us, ‘I stumbled on your station, I’m not religious but I enjoy listening.’ And I think people detect an integrity and sincerity in us.”

There’s another crucial factor: Spirit offers something quite different in an increasingly, and boringly, isotropic media universe. Robbie Smyth says: “They’re appealing to the flipside of what we usually hear.”

Rob Clarke describes Spirit as “refreshingly different”, especially in their positivity. “A lot of media has that philosophy – ‘if it bleeds, it leads’ – but life is more complex than that,” he adds. “While we don’t ignore bad news, we try to find good news stories as well.”

We should also note that Spirit has a 50-50 on-air gender split, which makes it unique and puts to shame other stations that are great at advocating progressive values, not so great at actually sticking a woman behind the microphone. Again, it’s not ideological – they simply got the best people for the job.

“The station is in a good place,” he concludes. “We have a great team and great atmosphere, with a real sense of community; they’ll go the extra mile for you.”

The best of Christian values, indeed.