NAB:The Road To Digital

It's a fact that with every passing month, more and more stations are opting to turn on the digital switch. Many of them have accomplished this through the installation of low and medium power DTV transmitters. But there is growing concern among manufacturers that these "get your feet wet" rigs could lead some stations into fox holes and tank traps they never imagined.
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It's a fact that with every passing month, more and more stations are opting to turn on the digital switch. Many of them have accomplished this through the installation of low and medium power DTV transmitters. But there is growing concern among manufacturers that these "get your feet wet" rigs could lead some stations into fox holes and tank traps they never imagined.

There are many stations making an honest attempt to get their DTV operations up and running. Unfortunately, they often don't give much regard to the long-term consequences of certain short-term solutions. Their attitude is that they can start right now with an upgradeable low power transmitter, add more power later, and keep expenses under control along the migratory path.

The issue is that they've started their thinking from the wrong end of the problem. RF transmitter manufacturers at the NAB convention were busy pointing out that stations need to start their DTV RF facility planning by first establishing what sort of transmitter stations want to end up with when they reach their final medium or full power goal.

Instead of looking at the quickest way on the air, transmitter manufacturers warn that stations can avoid the "you can't get there from here" syndrome by taking a hard look at the transmitter they intend to end up with.

After making that decision, manufacturers say stations can make sound decisions about which transmitters have a reasonable migratory flight plan, one that makes sense today and tomorrow, and one that has a minimum of throwaway parts and pieces along the way.

Stations moving into UHF DTV after a long history of VHF operations are the most at risk here. VHF TV stations operate with a main and backup transmitter. Adding a UHF transmitter eats up floor space at the transmitter site. RF sites are notoriously small, with cramped quarters usually being the order of the day.

Aside from having to learn the nuances of UHF RF operations, when stations put that new UHF DTV rig into the facility, the transmitter's footprint becomes a major consideration. Naturally, starting with a low power, smaller transmitter can be appealing. Still, the day will come when that transmitter will grow, and it'll have an even larger footprint.

The situation becomes all the more difficult when engineers address the question of what to use as a DTV alternate, or backup transmitter. Some transmitter companies offer transmitters that can run up to 500 or 1,000 W, with that power as their final destination. From a cost and space point of view, they make sense because they will (1) get you on the air now, (2) won't take up much space, (3) won't cost an arm and a leg, and, finally, (4) can be used later as the alternate or backup transmitter. Several new IOT tubes that debuted at the NAB convention this year might help station managers with the issues discussed above. The new IOTs, notably from CPI/EIMAC, EEV, Northrup Grumman (formerly Litton), and Thales Electron Devices, use a variety of designs to achieve marked improvement in operating efficiencies.

With the advent of these new products, the prospect of chopping down those high power bills has become brighter, but the latest IOTs also bring a new perspective on why starting DTV operations with full power makes economic sense. For example, would a $700,000 full power transmitter be more appealing if it could cut your power bill in half? And you don't have to worry about a non-upgradeable low power DTV transmitter that you will have to replace anyway.

The initial investment is high, but the immediate saving in power bills would somewhat offset monthly payments on that transmitter. Put another way, the savings would eventually pay for the transmitter.