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How low can you go?

DTV transmitter manufacturers offer products designed for broadcasters looking simply to comply with FCC regs 3/24/2002 07:00:00 PM Eastern

With a sigh of fiscal relief,
broadcasters are taking a whole new look at their requirements for getting on the air in digital. For many, the cost of an appropriate transmitter could be as little as $50,000, maybe even less, thanks to a Nov. 8 ruling by the FCC.

The ruling states that stations are no longer required to replicate their analog coverage but only have to cover their city of license. The result, according to Dale Mowry, vice president, transmission systems, at Harris Broadcast Division, is that a sizable number of broadcasters will be going on with as little as 1 kW. This means a large number will be exploring new solutions at the upcoming NAB exhibition.

Harris's market tracking shows that about 640 broadcasters have ordered some transmission equipment. This leaves some 900 stations still uncommitted. About 500 of these, Mowry notes, are commercial stations, the public stations having an extra year, until May 2003, to get on the air.

The number of these uncommitted stations likely to take inexpensive low-power options appears high, according to Dick Fiore, senior vice president of sales at Thales Broadcasting and Multimedia. He estimates that roughly 80% need no more than 100 W of transmitter power output to meet the FCC requirement of 48 dBu.

Larcan President Jim Adamson says the DTV allocation table has a lot of 50,000-W ERP allocations. "It's not difficult to achieve that with 5 kW and even less because antenna gains of 20 to 25 times actual power are not uncommon."

Although the low-power approach doesn't address the long-term potential of a widespread demand for digital reception, which would require transmission beyond the city of license, transmitter manufacturers expect low-power units purchased today to become backup transmitters for subsequently acquired higher-powered units. Also, many of the low-powered, solid-state transmitters are upgradable.

With its roots as a manufacturer of low-power transmitters and exciters, Axcera offers several options. Its DT800A series of digital transmitters runs from 50 W to 3 kW average power. An option to this line, DTValue, includes the transmitter and all the encoding needed for standard definition, along with the Sencore Investigator system-monitoring package.

"Everything is in one rack, including the output mask filter," says Director of Marketing Rich Schwartz. "You plug your video input into it, connect your transmission line to the output, and you're on the air." The transmitter ranges in cost from less than $50,000 to $200,000. DTValue, which can be added to any of Axcera's transmitters, costs another $50,000 to $60,000.

The DT800A series is not upgradable, nor is the DT840A tube transmitter. The latter is aimed at the large group of broadcasters that need only 5 kW to get on the air in digital. Air-cooled and using a Diacrode amplifier, it costs about $200,000.

Meanwhile, Axcera will introduce a low-power upgradable system, the DT Gateway, at NAB. Costing $100,000 to $150,000, it can go on-air with power levels up to 350 W. It can be upgraded with the addition of IOT power amplifier cabinets, which turn it into a Visionary DT transmitter with power of 12 to 180 kW.

Mark Polovick, national sales manager for Ai (formerly Acrodyne Industries), will be telling prospective clients at NAB about a low-power line from Rohde & Schwarz, which his company represents in the U.S. The product is a tabletop version of the manufacturer's air-cooled line, with power from 10 to 200 W. The solid-state transmitter, depending on power, can cost less than $60,000.

In its own line, Ai will offer a stripped-down version of its Quantum IOT product, the Convertible. The tube and related power supplies are removed from the Quantum, which can be configured from 250 W to 1 kW average solid-state power. It can be converted to full power by adding back the IOT and related gear. The stripped-down version, at 500 W, costs around $125,000. The high-power version is less than $500,000.

Rohde & Schwarz also has an air-cooled digital transmitter for handling up to 1 kW. The station can subsequently convert to high power with a Quantum IOT transmitter without the driver modules or exciter, using these elements from the original transmitter so that this investment is not lost. The low-power NV7081E series costs well under $100,000 for 1 kW. Conversion to high power costs $400,000 or less.

The Affinity transmitter from Thales was first seen at Europe's IBC trade show and will make its NAB debut, offering power from 50 to 800 W. Vice President of Engineering Brett Jenkins says it was designed originally for telco use in broadband delivery before being migrated to UHF for low-power digital transmission. He points out that the transmitter has small space requirements, with amplifiers and power supplies requiring only six rack-units for up to 200 W.

The Affinity uses hot-swappable, broadband LDMOS amplifiers. Thales also plans to offer it with a single standard-definition encoder and PSIP data integration. The solid-state-transmitter–based system can be placed at the transmission site, according to Jenkins.

An upgrade strategy, in the Beachhead line, is to start out with solid-state amplifier pieces and add tubes later to increase to 100 kW or more. Meanwhile, the Ultimate product line has an upgrade strategy for those wanting to start out at 1kW or less and remain in solid state while going to 5 to 10 kW. The Thales products start at under $50,000 and cost up to $100,000 for 1 kW.

The most recent low-power offering from Larcan is the Magnum system, which begins at 21/2 kW, for about $235,000, and is upgradable in solid state to 20 kW or more. According to Adamson, the broadband design, using LDMOS amplifier devices, is modular, with multiple power supplies. He cites user-friendly graphical control interfaces for monitoring and space-efficiency, with a 5-kW transmitter occupying two cabinets and a 10-kW taking up three.

Although Harris's Ranger transmitter can cost below $80,000 for 500 W, Mowry expects significantly more orders for its Diamond transmitter, which goes from 1.8 to 30 kW, from $140,000 to about $1 million. He reports that both transmitters have significant reuse in an upgrade situation. For the Ranger, he notes, about 70% of its value is reusable in a higher-power transmitter because it has the same exciter as the larger ones. The amplification modules also are reusable in the Diamond. The Diamond, if purchased at 1.8 kW, can be upgradable to any power level with 100% reuse.

A Harris introduction at NAB will be the Apex ATSC digital exciter, which offers nonlinear adaptive correction. All of Harris's previous exciters had linear adaptive correction to optimize signal-to-noise performance and enhance the coverage area. The nonlinear approach, according to Mowry, will also improve the shoulder performance of the transmitter, enabling operation at higher power levels.

Itelco USA has transmitters aimed at 50 W on up and that the FCC's new ruling has significantly enhanced interest in the low-power product, according to Tom Newman, director of sales and marketing.

"While some stations are still looking at low-power transmitters as a backup for later on, many more are looking at the upgradability aspect," he says. "Our solid-state transmitters are all upgradable, and the higher-power transmitters are all upgradable by adding more tubes."

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