RF EXPRESSEfficiency Rules The RF World

There was a time not so long ago when television transmitter exhibits at NAB conventions made for a great place to rest. You could easily find a transmitter to lean against. Occasionally, you'd see someone sitting on the floor, using a transmitter as a backrest. There wasn't much new each year. At least not until the Eimac Klystrode tube showed up in the Comark booth. That development set the stage for bringing television transmitters front and center.

The name of the game became efficiency, as in IOT efficiency versus the conventional klystron. Power-guzzling UHF transmitters would become a thing of the past, and the race for higher and higher efficiency UHF tubes was on. L3 Communications developed the Constant Efficiency Amplifier (CEA), and e2v (EEV) was hard at work on their 3- and 5-stage ESCIOT (Energy Saving Collector IOT). Meanwhile, there were great strides being made with MSDC tubes. Everywhere you looked, efficiency (coupled with DTV designs) changed the way stations stacked their priorities for new transmitter purchases.

Over the years, price, reliability, and factory backup were key at the point of sale. But that was about to change.

At L3 Communications, Buzz Miklos says that if the industry switched to the CEA, the energy savings would equal a freight train lugging 200 cars of coal a year. Early on, EEV was a lot more secretive about their test results and savings projections. Meanwhile, CPI and Thales Components were pushing ahead with their new designs.

Today, tube efficiency is a key feature in transmitter sales presentations. Recently, L3 Communications confirmed that it had received a substantial order for its CEA tubes. That's been followed by an announcement from e2v that it has received the first orders for its ESCIOT products. According to e2v, the initial shipments will be made to Ai, Sinclair Broadcasting Group, and Axcera.

Mike Kirk, e2v's vice president of communications, stated that "It's most encouraging that so soon after demonstrating efficiency levels to our customers [at NAB], they have placed the first of what we believe will be many more orders for these devices."

Ai told us in late August that it could have an ESCIOT-equipped transmitter ready for the marketplace by the fourth quarter of 2003, while Thales says it has a number of its Paragon CEA-equipped transmitters already on air. With a lot less fanfare, energy-efficient MSDC tubes are definitely in demand.

While it was rumored that Thales had basically designed the Paragon transmitter to accommodate the CEA tubes, Dick Fiore is adamant that "We're not in the business of selling tubes. We're selling transmitters, and we'll put in whatever devices the customer asks for."

At Harris, you can look for a "ground-up" new transmitter aimed at utilizing the newest high-efficiency devices. Harris says there's no date set for its unveiling, but it would be no surprise if the company shows up at NAB 2004 with at least some official word on its design features.

Analog Is Still King

With analog still bringing profits to the bottom line, and with few stations seeing a profit from their DTV operations, it's no surprise that transmitter manufacturers are still seeing steady analog sales.

Fortunately, all the transmitter manufacturers' newest rigs are capable of switching over to DTV. That's mainly an exciter consideration, but depending on the difference between the analog channel and the DTV allocation, there could be other ancillary RF products involved.

As for the exciter, the changeover could entail nothing more than swapping out a few cards. Or it could be as extreme as replacing the exciter. Interestingly, while the power-packing, high-efficiency amplifiers are vastly improving transmitter efficiency, today's exciter is solid state, where efficiency isn't a feature.

What About Solid State?

No doubt we'll see some new solid state devices coming to the market, but not any time soon. For now, the silicon carbide device remains tempting, but elusive.

Those who prefer the comfort factors offered by solid state transmitters are taking a somewhat different view of efficiency. Admittedly, their efficiency ratings are in the range of the old, conventional klystron. Still, solid state buyers are looking at the cost of ownership figures.

It's well established that current solid state devices have excellent MTBF (meantime between failure) numbers. Coupled with hot-pluggable modules, these transmitters translate to cost-effective operations.

Calculating Efficiency

Ask any transmitter manufacturer about the importance of tube efficiency at the point of sale, and they'll tell you it's at the top of the list. Problem is, there are many ways to figure efficiency.

If you make a straight comparison between a high-efficiency tube and a conventional klystron, that's fairly safe. And then, of course, are you calculating in analog or DTV?

The savings over a five-year period with the new high efficiency system, taking depreciation into account, would be huge with regard to the cost of ownership. Not surprisingly, power bills are dropping dramatically.

But if you compare one tube against two, calculate in the exciter and ancillary products needed, or compare against an MSDC tube--the answers are not so clear. Or, are you looking at the whole RF plant? What's more, the actual saving are dependent on local power rates and peak use rates.

One thing's for certain: All the new tubes and the new transmitters are delivering dramatic savings on the power bill, the single largest operating expense stations encounter.

Rich Schwartz at Axcera makes an interesting observation: "If a station is considering selling, the addition of a efficient transmitter and high-efficiency tubes would have an immediate, positive effect on bottom line profits, making the station a much more attractive buy. It's a quick fix."

Perhaps a station's accounts payable person may provide the most accurate efficiency savings number. But make no mistake about it, transmitter booths at NAB are no longer a safe haven from the crowded aisles. In fact, in 2004 they'll probably be a beehive of activity, because efficiency--no matter how you calculate it--rules the day.

Ron Merrell is the executive editor.