07.22.2009 10:28 AM
Originally featured on BroadcastEngineering.com
View from Detroit: Pros and cons of 2GHz BAS channels

Editor’s note: Part I of this story,Detroit stations transition to new 2GHz BAS channels,” examined making the switch to the new ENG band plan being paid for by Sprint Nextel. This article looks at some of the early lessons learned.

The experience of working with the new digital 2GHz Broadcast Auxiliary Service equipment in service in Detroit since July 11 has certainly been a change from using the old analog gear — in terms of both positives and negatives — says WDIV-TV manager of news operations Jeffrey Liebman.

On one hand, the new digital equipment offers much more flexibility than the analog equipment it replaced; on the other, it comes with its own unique peculiarities that must be anticipated and planned for, he says.

According to Liebman, the Post-Newsweek Stations’ new 2GHz BAS equipment has made live shots possible from places where they previously could not be done. The station uses its new MRC MTX5000 radios with two presets — one allowing optimal video signal and the other with “a little more error correction in it” that allows shots from farther way, he says.

“The city of Brighton is located quite a distance away (about 40mi). Traditionally, WDIV could not get live shots from there,” Liebman says. “Using the new digital band, we’ve been able to get shots from Brighton and other areas where we previously couldn’t.”

The ability to bounce COFDM signals to a receive site is another plus. “In the metropolitan area, we are dealing with tall buildings and a lack of direct sight to a receive site,” Liebman says. “Bouncing the signal has opened up many possibilities.”

However, there’s more to the story of digital 2GHz BAS equipment than increased range and signal bouncing. There’s also a downside, which can be managed and overcome with adequate training, Liebman says.

“The con is, it isn’t like the old analog days when you could get away with power up being maybe 10 seconds in the most optimal environment,” Liebman says. “In the digital world, we are finding that process can take as long as 40 seconds to a minute.”

This added time can make it difficult at the receive site. “The way the producers block these shows — you’re running in an out of receive sites, and there are television stations with a lot of trucks out there sharing the same receive sites — you run into some difficulties powering up and powering down,” he says.

“When we are powering up sometimes, we get a burst of signal. At the receive site, you see black. If we get that burst of black, it may not really be black,” he says. “It’s probably a burst of signal, and then the picture will pop in.” According to Liebman, it’s also possible to have the picture pop out while an error correction build is going on or to experience “color contrast going wild before popping in.”

“The changeover has put a tremendous amount of pressure on our receive operators. It’s forced them to look back at their receivers so they can actually see on a spectrum analyzer the spectrum come up and the nice beautiful cliff or, conversely, nothing,” he says.

However, dealing with these new challenges is simply a matter of relearning, Liebman says. “The biggest thing we’ve learned is that it’s important to emphasize training on the receive side and for the transmission folks,” he says. “That team plays one of the biggest roles in this whole changeover.”

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