Broadcast

 

Korea launches mobile TV
The world’s first commercial terrestrial mobile TV services were launched in Korea on 1 December 2005—supported by Radio Frequency Systems.

 

The explosion of mobile television trials and services around the globe are a certain sign of things to come. Third-generation cell-based systems might have leapt to the front in terms of deployment, but there is also vast merit in using broadcast models for delivering TV signals to handheld devices. The much lauded digital video broadcasting-handheld (DVB-H) technology is one option for this—however, on 1 December 2005, South Korea launched the first phase of a network based on an alternative technology, known as digital multimedia broadcasting (DMB).
Like digital audio broadcasting (DAB), DMB technology is based on the orthogonal frequency division modulation (OFDM) based ‘Eureka 147’ standard; however, DMB offers a good deal more than DAB. In addition to DAB’s digital audio signal with accompanying ancillary data (such as radio play lists), DMB’s offering includes the real-time viewing of television and data on portable handheld devices. It is anticipated to be a viable rival for DVB-H over the coming years; and, for the moment at least, Korea’s new terrestrial DMB service is the world’s first commercial mobile television service based on terrestrial broadcasting models.
Trials of Korea’s DMB technology began back in 2002, carried out by South Korean government broadcaster, Korean Broadcasting System (KBS). Operating in VHF Band III (174 to 230 MHz), the service proved immensely popular in a market that has embraced telecommunications mobility. Now both KBS and the Munhwa Broadcasting Corporation (MBC), Korea’s second national broadcaster, are deploying nationwide DMB networks, supported by Radio Frequency Systems.

Kitted out at Kwanak
According to Norm Franke, RFS Broadcast Sales Manager Asia, RFS supplied a complete antenna system for the original KBS trial at Mount Kwanak, one of Seoul’s two main broadcast sites. The trial system incorporated a four-level panel array, RF feeder system and digital power monitoring technology. “That antenna has now been removed to make way for a new RFS six-level panel array, which broadcasts the main DMB service at Mount Kwanak,” says Franke. “The original antenna is being reused at one of KBS’s smaller Seoul sites—Yong Mun San—also for DMB transmission.”
RFS has also supplied two DMB antenna systems for MBC at Mount Kwanak: the main service is broadcast through an RFS six-bay top-mounted turnstile antenna, while a smaller two-bay panel from RFS provides standby services.
MBC is also broadcasting its DMB service from Seoul’s other main broadcast site, Namsan Tower—a 237-meter (777 foot) tower that stands almost half a kilometer (third of a mile) above sea-level and is one of the city’s most recognizable landmarks. Built in 1980 as a broadcast transmission tower for television and radio services, Namsan Tower also houses a revolving restaurant and has hosted more than 20 million visitors to the site.

No room at Namsan
“The challenge at Namsan was the lack of space available on the tower for a new DMB antenna,” says Franke. “There was simply not the scope to extend the tower or squeeze anything additional onto the structure.”
The solution, says Franke, lay in a new four-dipole Band III panel from RFS—the ‘662’ series—which has two horizontal and two vertical dipoles mounted in a square configuration. This allows it to support both horizontal and vertical polarized services in a single array. The antenna for MBC’s existing analog TV service—utilizing horizontal dipoles—was removed, and directly replaced by an equivalent RFS four-dipole 662-series antenna. “It acts as two completely separate systems,” Franke says. “The DMB service is broadcast via the vertical dipoles and the analog TV service via the horizontal dipoles.”
Since the DMB and analog TV services are effectively interleaved, the design of the panel required careful attention. “It’s imperative that the antenna maintains good pattern performance for both the horizontal and vertical polarized signals,” Franke says. Other features of the 662 panel include a robust design with stainless steel radiators to withstand harsh environmental conditions, and a range of connector options. It also has high power handling capacity and can be used for circular or elliptical polarized applications, as required.
Although the DMB mobile television service is only available in Seoul at present, the South Korean Ministry of Information and Communication (MIC) plans to expand the service nationwide over the next year or so. This terrestrial service complements the country’s satellite DMB service, launched in May 2005.