Digital audio broadcasting (DAB) is rapidly gaining popularity in the United Kingdom and other countries as it offers much improved sound quality, and the opportunity for many new channels, compared with traditional analog radio.

DAB technology utilizes a section of the radio spectrum that has been used in many countries for VHF television broadcasts.

None of Hong Kong's four TV stations broadcast on VHF channels, which would seem to clear the way for DAB.

The Office of the Telecommunications Authority, which studied most of the DAB spectrum last year, concluded that space could be made available for at least seven DAB signals. That would open the door for at least 42 DAB radio stations - a leap from the present 13 FM and AM stations here - as each DAB signal can carry six separate CD-quality broadcasts at the same time.

However, TY Chan, OFTA's planning head, said the mainland's State Administration of Radio, Film and Television has told OFTA that three of the seven spectrum spots OFTA identified would interfere with VHF broadcasts from stations in Guangdong province, particularly signals beamed at islands south of Hong Kong that are administered by Zhuhai.

The mainland regulators said two of the proposed DAB frequencies could be used as long as no transmitters are used in border areas, leaving only two full-use frequencies.

Chan believes Hong Kong needs to identify four frequencies for DAB broadcasters so that each of the three existing radio broadcasters can have a frequency of their own, with at least one left over for new entrants. He doubts whether any broadcaster will be willing to forego transmissions in border areas since that would omit fast-growing districts such as Tin Shui Wai, Tung Chung, Fan Ling and Yuen Long.

As a result, Chan said OFTA is now scrutinizing a small section of the DAB spectrum omitted from the first study, with hopes of identifying at least two other potential frequencies.

In the mainland, this piece of the spectrum falls under the jurisdiction of the Ministry of Information Industry, which will have to be consulted on any DAB proposals in Hong Kong.

OFTA hopes to issue a new frequency plan next year. Though there are no VHF broadcasters here, parts of the DAB spectrum are currently used by TV stations for internal transmissions between their studios and broadcast towers, and by various government departments for internal communications.

The TV stations could switch to a different type of connection but, because of recent investments in new systems, Chan doubts whether some of the government users can be budged.

Meanwhile, neither the government nor Hong Kong's three radio broadcasters have any plans to introduce regular digital broadcasts.

Radio Television Hong Kong is making test broadcasts of its seven stations using DAB, but lacks approval and funding to make those permanent.