LOUISVILLE, Ky.–The Louisville market has a busy over-the-air presence with nearly 30 TV stations. WDRB Media operates two of Louisville’s network-affiliated stations: WDRB-TV (Fox) and WBKI-TV (CW), both of which had Phase 6 repack assignments. WDRB Media’s corporate owners, Block Communications, standardized on GatesAir transmitters during the recent repack for their stations in Illinois, Kentucky and Ohio, replacing long-operating tube transmitters from other manufacturers.
A SOLID APPROACH
GatesAir made sense for many reasons, including a generous warranty that represents their customer service emphasis. New transmitters were required given the substantial frequency shifts (Channel 49 to 32 for WDRB; Channel 51 to 16 for WBKI), and GatesAir’s solid-state designs were impressive in both performance and maintenance evaluations. GatesAir’s energy-efficient designs were of exceptional importance given the very high TPOs (transmitter power output) required.
Our transmission facility sits at 964-foot elevation, with signals transmitting from a 1,000-foot tower. Clear sightlines ensure we reach viewers 60 miles from the tower. Our new Maxiva ULXTE liquid-cooled UHF transmitters are designed to optimize that market coverage, with WDRB’s ULTXE-120 model maximized for its 1MW ERP (68kW); and WBKI’s ULXTE-150 model operating at 725 ERP (58kW). The ULXTE-150 has extra headroom for an expected power raise this summer, and another possible boost in the future.
While our previous transmitters were liquid-cooled, moving to solid-state required an entire plumbing refresh and a completely new liquid-cooling infrastructure. Nine heat exchangers were installed just outside the building, while the installers from RF consulting firm Jim Stitt and Associates moved the multicabinet transmitters into their new positions. Lines were run from the transmitters to the redundant Maxiva pump modules, which transfer heat to the outdoor exchangers. This energy-efficient process keeps our cooling bills as low as possible.
Solid-state offers several benefits when it comes to liquid cooling. Our old system required SR-1 ethylene glycol, which needed a complete refresh every three years. The Maxiva system uses off-the-shelf Prestone, requiring little maintenance beyond removing some particulates with a strainer upon adding.
Opening the front cabinet door reveals a beautiful layout that is easy to grasp. There is a minimum of parts, with redundant power amplifiers and power supplies. Each module is about 700W; if one is lost, GatesAir’s adaptive correction software masks any performance drop. With the front-panel GUI, we can monitor the status of each module, identify a power supply issue and understand when an amplifier firmware upgrade is needed.
Our ULXTE transmitter includes redundant GatesAir ATSC3-ready Maxiva XTE exciters, which brings impressive performance and design traits. GatesAir builds a mini UPS and its real-time adaptive correction (RTAC) software into the XTE. The latter is useful for monitoring signal-to-noise and shoulder performance, which will often point to problems in the antenna or transmission line if outside the threshold.
The XTE currently shows our shoulders at –47, which is 10 Db better than the FCC specification. It was also much easier to obtain this number compared to the days of tube-type technology. If we reduce power, the RTAC software will re-adapt the shoulders to appropriate levels. And while RTAC is designed to keep the signal within its frequency, the ULXTE performs so well it is hard to imagine when that correction would be required.
As we look ahead to NextGen TV, we’re running our new RF systems with the confidence that our Maxiva transmitters and exciters will seamlessly transition to ATSC 3.0. The additional headroom will also ensure we can add new NextGen TV services when needed.
Gary Schroder is the chief engineer of WDRB Media. He can be reached at firstname.lastname@example.org.
For more information on GatesAir visit: www.gatesair.com/.
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