Low-quality AM band only option for channel

PUBLISHED : Friday, 25 January, 2008, 12:00am
UPDATED : Friday, 25 January, 2008, 12:00am

The application for a new AM radio channel by talk-show-host-turned lawmaker Albert Cheng King-hon has revived local interest in the broadcast band, but experts say its technical constraints are difficult to overcome.

Once dominant, AM radio has largely been replaced by FM because of the comparative quality of signal, especially in urban areas.

'Even starting a car or turning on a neon light will disrupt the AM signal. Audiences will hear a dip in volume and severe interference when they get close to electrical devices,' said Ho Wing-leung, president of the Hong Kong Amateur Radio Association.

What's more, FM radio easily covers the musical range of the human ear, which is why it sounds better than AM.

Edward Yung Kai-ning, director of City University's Wireless Communications Research Centre, added that music broadcasting posed another technical constraint.

Without the benefit of being able to broadcast in stereo, 'the quality of music broadcast by AM radios is like hearing someone sing through a telephone speaker', he said.

Professor Yung said AM broadcasting's main role was providing storm reports for fishermen, as interference with the signal on the water was minimal.

But applying for an AM channel appeared to be Mr Cheng's only option, as all seven FM frequencies are occupied by the three major broadcasters.

Only six AM channels - four belonging to public broadcaster RTHK, one to Commercial Radio and one to Metro Broadcast - are in service, and none of them plays a particularly major role in the radio market.

According to an RTHK survey last year, fewer than half a million listeners had tuned in to RTHK 5, the most popular AM channel, in the previous seven days while more than 1.5 million people were listening to RTHK 2, an FM station.

During an interview with RTHK yesterday, Mr Cheng expressed confidence that the possible radio station would overcome the disadvantages of the AM frequency, saying it was a question of demand rather than technology.

He admitted reception of the AM signal was poor in most vehicles, and that to receive AM at home one would need an entirely new aerial.

'Of course, everyone knows that we'd rather apply for FM, but that's not possible. It's not ideal - we all know that - but we are confident we can overcome this problem.'

He said if the content of his programmes attracted listeners, then the public would seek out radios with the AM band and businesses would upgrade their AM receiving technology.