Agrowing number of low-power stations are quickly recognizing the potential of digital transmission for expanding service offerings, raising video quality and creating new revenue streams. Now, these stations can follow the lead of KAXT-CA, a Class A community station based in San Jose, CA. This year, KAXT launched an unprecedented digital ATSC television service capable of broadcasting up to 20 MPEG-2 video and audio services within the 19.39Mb/s ATSC spectrum. Using advanced video processing solutions from Harmonic, transmission equipment from Linear Industries, and PSIP generation from Triveni Digital, KAXT is currently broadcasting 12 video channels and four audio channels and is already planning to add four more audio services.
When planning the digital switchover, KAXT faced a number of challenges — the largest of which was finding a cost-effective technology solution that could accommodate the station’s aggressive launch schedule. After some deliberation, the station decided to offer at least 10 digital SD channels with capabilities for eight radio services as well, which required a powerful encoder. Since KAXT was building its digital service from the ground up, engineers soon realized that the bottom line price was not significantly affected by the addition of more channels. By using adaptive encoding techniques and advanced look-ahead processing, the higher channel count could allow for even more flexibility in the statistical multiplexing variables; with more channels, the software can spread the quality hits out across more channels.
For the new digital service, KAXT chose Harmonic’s Electra 5000 encoders, DiviTrackIP statistical multiplexing and NMX Digital Service Manager to compress and manage the video and audio services efficiently. Triveni Digital’s GuideBuilder PSIP generator manages the large number of virtual channels and EPG metadata files and feeds the carousel to the Harmonic ProStream 1000 remultiplexer over IP. The GuideBuilder PSIP generator also provides a future-proof path to mobile DTV.
KAXT’s new digital operation features an all-ASI plant design from the studio to the transmitter site on Mt. Allison. The ASI output from the Harmonic ProStream remultiplexer output is fed into a Mosley microwave system and delivered on the mountain straight to the exciter’s ASI input. The Linear Industries AT71K0-1 1000W digital UHF transmitter and AT7001 exciter complete the groundbreaking system with advanced linear and nonlinear precorrection to provide the most pristine signal possible.
The end result of this collaborative deployment allows viewers in KAXT’s diverse market to receive and experience a much broader array of multicultural content from a single source. KAXT is the first station in the United States to offer such a large range of programming in the ATSC 19.39Mb/s spectrum. The solutions from Harmonic, Linear and Triveni Digital make it possible to deliver more channels with excellent video quality at ultra-low bit rates, when compared with the station’s previous analog service, and in a cost-effective manner that met KAXT’s budgetary requirements.
New studio or RF technology — station
Submitted by Harmonic
Harmonic: Joel Wilhite
KAXT-TV: Warren Trumbly; Ravi Kapur
Linear Television: Perry Priestly
Triveni Digital: Mark Rushton
Harmonic: Electra 5000 encoders, DiviTrackIP statistical multiplexing and NMX digital service manager,
ProStream 1000 remultiplexer
Linear Industries: AT71K0-1 1000W digital UHF transmitter, AT7001 exciter
Triveni Digital: GuideBuilder PSIP generator