Dielectric Combines Repacked UHF Stations into Common RF Architecture

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Dielectric highlighted the launch of a unique ATSC 3.0-ready multi-channel combiner and waveguide switching system installed at DTV Utah’s community TV transmission facility. The antenna manufacturer says it won the challenging multi-station repack project because of quick turnaround of a complex system that met all size and performance specifications.

DTV Utah owns and operates the facility, which houses transmission systems for nine Salt Lake City-area stations. Six of eight stations were repacked to new channel assignments. 

They broadcast from specialized multi-channel antennas (two main and one backup).   

James and James Consulting managed the project, including the design, integration, and commissioning of the Dielectric system. Consultancy owner Greg James was a former DOE for one of the repacked stations (KSL-DT) and intimately involved with the original DTV Utah facility design.

“The DTV Utah site is an interesting mix of public, commercial and independent stations, most of which operate on a common antenna system that changed with the repack,” said James. “The site is located 3,500 feet AGL and transmits with specialized antennas built for the original system in 1999. We had no way to retune the RF system for all these newly repacked channels, which meant we had to replace the combiner system.”  

The previous combiner — also a Dielectric system — had to remain operable during the transition. The old system and mask filters were located in the ceiling of the building, and could not be removed. The situation led Dielectric to develop what the company says is its most compact combiner.

“We had a 17×20-foot space for a tenth transmitter that wasn’t installed, and Dielectric designed a 14×16-foot system that could combine all of our channels and leave room for the tenth transmitter,” said James. “Of most importance, we had to install the combiner before integrating the new repack transmitters.”

The three adjacent channels required sharply tuned filters, allowing the full use of each channel’s bandwidth. While the group delay measurement is increased slightly from a more broadly tuned filter, the new GatesAir and Rohde & Schwarz transmitters in the facility provide the necessary correction, making the group delay at the channel edge negligible, according to James.

April 26, 2019

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