The presenters have changed and the song requests are different. But 40 years after being established by the Jewish Youth Voluntary Service, Radio Northwick Park is still brightening the days of patients at the Harrow hospital.

Marty Rose and Len Elman were in their early 20s when Northwick Park was built. At the time, they were already involved in weekly radio broadcasts run by JYVS members at other hospitals in the area. And after approaching the hospital administration, they soon found themselves in charge of a broadcasting studio.

For them and other volunteers from the now defunct JYVS, it was another opportunity to give back to their local communities. "We already had the chance to dig gardens or paint - this was just an extension," Mr Rose explained. "We enjoyed broadcasting and this was a way to cheer people up in hospital."

Radio Northwick Park launched in 1971 and quickly attracted hundreds of volunteers. It now broadcasts all day every day, has a vibrant website and is staffed by volunteers of all faiths.

The original studio - "where we used to play records, can you believe it now?" - has been revamped a number of times and the original presenters have long since left. "It's been a complete transformation," said Mr Rose, who hung up his headphones for the last time in 1985.

But the new generation of more than 100 volunteers is carrying on the good work. Elliot Isaacson was a schoolboy when he began helping out at the station. A decade on, he has a job in advertising but still makes time to present and co-ordinate volunteers.

"I was in Northwick Park for a knee scan, saw the advert and signed up," he recalled. "I'm delighted I did."

Its output is "just like a normal radio station", with news, competitions, reviews and discussions. Mr Isaacson's favourite slots are the request shows. Hosts go round the wards before they go on air, chatting to patients and asking for songs they want to hear.

"It can be hard to see patients in pain. You realise how lucky you are," he said. "But you just get on with it.

"We get such positive feedback - people love it. The other day someone said they had been waiting for us to come round.

"A five-minute chat can make a patient's day, especially if they haven't had any visitors. There was one guy whose family were all in Canada. They emailed asking for a request for him. He was so pleased with it."

Mr Rose recalled that "staff used to tell us that patients recovered quicker because they were listening. It took their minds off things."

For the volunteers, "it was a big social group. Lots of members went on to marry each other and a lot of us ex-members keep in touch. We all became friends through it."

Mr Rose, who still pops by the studio occasionally, appreciates that what he and Mr Elman created is in good hands. "I'm very proud when I go back," he said. "The people down there now are all doing the same thing we did, having a great social life and getting the programme done."

Mr Isaacson felt it was "nice to carry it on and to show the old members what we have done. It's amazing the station has come this far. Hopefully the founders are proud of the direction we are taking it in."

Northwick Park is the most listened-to station in the hospital, despite patients having access to BBC channels, Magic and Talksport.

But despite its popularity, money is required to ensure its survival. It is not funded by the hospital and around £8,000 is needed annually to cover running costs such as electricity and equipment.

"It's not the BBC with billions of pounds to spend," Mr Rose said. "But it makes people very very happy. That's what it's all about."