Handling interference

Handling interference

Published: ASIA

Seoul’s Digital Media City (DMC) certainly lives up to its name. Founded in 2002 on the site of a former landfill close to the Han River, today the area has been transformed into a beacon of high-technology. Increasing numbers of South Korea’s most powerful companies are based in the district, including leading names from the film, gaming and music industries. Crucially, it has also become the home of Seoul’s broadcasting sector.

But for all of the advantages that DMC offers to its residents, it presents a unique and serious problem to the broadcasters who work within its high-rise facilities – interference. With so many stations based within the same relatively small area, it is becoming increasingly difficult to find clear RF space.

‘There are so many big stations in this area that I can’t count them – there are too many,’ explains audio engineer Lee Chae-Hyung, whose work with broadcaster SBS Medianet recently led him to search for a way to counter the problem. ‘It’s not just the amount of stations – each of them has built multiple studios. There must be thousands of wireless channels all being used at the same time because in this building alone there are 86 channels, plus in-ear monitoring and IFB. The number of wireless channels in this area must be in the thousands.’

The building to which Mr Lee refers is Prism Tower, the new home of SBS – one of South Korea’s three big names in broadcasting alongside KBS and MBC. SBS Medianet is an independently-operated sister company to SBS, running seven highly popular cable channels from six dedicated studios all based on the eighth, ninth and 10th floors of the tower. Included in the company’s portfolio is SBS Plus, delivering drama and entertainment programming; sports channel SBS ESPN, a collaboration with the US network of the same name; SBS CNBC, delivering economic news and analysis and co-owned by Comcast; the SBS E! entertainment channel, SBS Golf, which is dedicated to Korea’s love for the sport, SBS MTV and Nickelodeon Korea.

All six studios are clustered together across the three floors, each with its own equipment-studded control room. But as if that wasn’t already a reasonably crowded space for RF, SBS itself also operates a major studio on the third floor of the same building, while as many as four other huge broadcasting set-ups are located within a 305m radius. ‘MBC is also building its new facility just across the street,’ continues Mr Lee. ‘The two buildings are only 50m apart.’

The challenge presented by the environment becomes clearer still when you consider the type of content that SBS Medianet broadcasts, particularly with its news and sports channels. Mr Lee estimates that ‘as much as 80 per cent’ of the programming is live-to-air. In the world of SBS Medianet, a single RF drop-out is a disaster.

Pro Audio Asia is visiting Prism Tower sometime after Mr Lee and his colleagues confronted that challenge and ultimately overcame it thanks to a technology that was launched midway through their search – Shure Axient. The US manufacturer’s flagship system first presented itself as a possible solution during the Koba exhibition, when Mr Lee visited a seminar hosted by Shure distributor Sama ProSound.

‘I prepared for a long time before this project – I researched all of the possible wireless systems in the market,’ the engineer explains. ‘I was looking for the most stable system on the planet, and while I was in the middle of my research, Axient came out. It grabbed my attention! One of the most interesting things for me was the remote monitoring. We don’t have any assistant engineers - if we have any problems during a broadcast then the engineer has to leave the desk and come all the way into the studio. But with Axient you can monitor the status of all of the transmitters from the control room. Then of course I learned about the system’s Interference Detection and Avoidance automatic frequency switching system, and thought it was fantastic because I was so worried about RF instability in the DMC area.’

What followed is arguably the first high-profile broadcasting reference project for Axient within the South Korean broadcasting sector. For while the system has found a home within theatre-sound and the live market, broadcast remains staunchly conservative in Seoul.

‘Of course I have known Shure as a brand for a long time but not really within broadcasting applications,’ Mr Lee continues. ‘Before the installation we considered a different brand which is generally considered the standard here in Korean broadcasting. I am actually responsible for choosing Axient over that brand. Many people within SBS Medianet wanted to buy a different system but my colleagues and I believed that Axient would be more reliable in this environment.’

A total of 42 channels have now been installed, all supplied by Sama ProSound, whose Hojo Jeong led the challenging project. ‘Installing the hardware itself didn’t take very long but figuring out how to set-up the RF perfectly for their system took a long time, around two or three months,’ he recalls.

Nor were the challenges limited just to the crowded RF space. ‘We came up against other issues rather than just RF,’ remembers Mr Jeong. ‘The SBS Medianet channels use a lot of lights and colour-changing LEDs within the studio sets. But those LEDs generate noise at their power supplies. If you have a very good ear then you can actually hear the noise when you stand in front of the power supplies – it’s at 16kHz. That affects the wireless systems. Even before we connected anything to the body-packs, the transmitters picked up the 16kHz noise and passed it out to the audio chain. The engineers could hear it through the board.’

He continues: ‘It was easy for them to cut it out with a low-pass filter but they are broadcasting over cable and the longer the cable the more loss you suffer, so they didn’t want to give up that 16kHz.’

To solve the problem, Sama ProSound consulted with Shure Asia and the manufacturer’s US office. Eventually, engineers visited from the Asia office to seek a solution on the ground. But no matter how much the situation was improved, the problem never quite went away. ‘There’s nothing we can do to completely prevent the interference ,’ explains Mr Jeong. ‘But we decided to prove that Axient was eliminating it as much as possible.’ Aware that some of the more traditional engineers within the broadcaster were doubting the decision to purchase Shure, Mr Jeong acquired competing systems and performed, in effect, a shoot-out. ‘The other systems grabbed the same noise but it was much louder,’ he says.

Touring the control rooms that accompany each studio, it becomes obvious how significant it is that SBS Medianet chose to break with tradition. Each equipment choice reflects accepted industry wisdom, from the consoles ¬– Studer Vista 9s in the larger rooms and Vista 5s in the smaller spaces with Yamaha DM 2000s throughout for redundancy – through to the reference monitors, all of which are from Genelec. When asked why these specific models were picked, Mr Lee consistently replies that they are ‘the standard in broadcasting’. Moreover, he adds: ‘Even then, when we have picked the most up to date and respected models, we gather huge amounts of information on each item of equipment and test everything for many hours. Nothing is selected until it is proven by us first.’ This is not the kind of place where engineers take chances on equipment – only the most reliable, most respected technology is welcome.

Part of the reason why, reflects Mr Jeong, is the high level of expertise amongst the engineers themselves. ‘The audio engineers at this station are very tech savvy, they’re really into technology,’ he explains. ‘They wanted to be able to control everything over Ethernet from a computer. Since they don’t have assistant engineers they need a system that they can control remotely from one central location. They tried to connect every possible item of equipment to Mac Pro computers via Ethernet switches, so they can operate everything from within the control rooms. The Axient channels are included in that, as are the Studer consoles – everything.

‘Also Shure has provided Wireless Work Bench 6 software, putting it onto the Mac Pros, so the engineers can monitor the status of the wireless microphones. They don’t even have to come over to the rack to check the Axient channels, they just sit in front of the console and watch the screen.’

Both Mr Lee and Mr Jeong are clearly very proud of the SBS Medianet installation, but when pressed Mr Jeong will admit that there are some minor alterations that he would like to make. ‘They should have omni-directional antennas because sometimes the presenters move around the set,’ he considers. ‘But at the time this system was designed that plan wasn’t confirmed.’

Nevertheless, in the crowded RF space of Digital Media City, SBS Medianet now has a wireless system capable of holding its own, while Sama ProSound has a reference project that may help Axient find a natural market. ‘The most important thing in broadcasting is stability,’ concludes Mr Jeong. ‘Customers won’t buy anything unless it has a very good reference project. There was a lot of pressure on this project because of that. But I was sure about Axient – I had confidence.’


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