WJFK-FM Launches HD Radio Quadcast

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The Embedded Importer control screen to access the HD2, HD3 and HD4 streams

The Embedded Importer control screen to access the HD2, HD3 and HD4 streams

The Importer also provides three channels of DTS Neural Audio pre-codec conditioning to optimize the multicast audio for the HD Radio codecs. WJFK uses the extended hybrid mode's P3 partition for an additional 24kb/s of capacity. The station divides its channel bandwidth among the four program streams within the total 120kb/s throughput of the MP3 mode.

WJFK had been using a Moseley StarLink fixed microwave STL system to transport the analog FM channel, main channel HD Radio and HD2 program audio to the transmitter site, along with a Moseley LANLink to transmit data. The StarLink remains in place to transport the main program channel as AES audio.

The station opted for a T1 system to transport the remaining quadcast signals. T1 offered a robust platform to transport multiple HD Radio channels. WJFK purchased and installed Ethernet-to-T1 extenders, which essentially extend the CBS corporate WAN to the transmitter site.

The previous multicast setup had both the Importer and Exporter at the transmitter site. WJFK upgraded and moved the Importer back to the studio to accommodate the quadcast but left the Exporter by the transmitter. To maintain Importer-to-Exporter synchronization (critical to preventing multicast dropouts), a GPS-referenced word clock was connected to the Importer's audio card word-clock input.

The newer FlexStar -200 Embedded Exporter replaced the previous PC-based HDE-100 Exporter. The Exporter takes the incoming audio stream and creates a delayed output for the analog audio input to the Exciter. It also encodes the Main Program Service for the HD Radio main channel, HD1, and multiplexes it with the Importer's incoming multicast IP stream from the Black Box LAN extender.

The HDE-200 Exporter provides an integrated GPS receiver with remote setup and monitoring capabilities, as well as a simpler and more flexible user interface. Its compact size and easier setup process helped to enable a fairly quick installation. WJFK was on the air with the quadcast within days of the transmitter's arrival.

At the transmitter, the main program from the StarLink feeds an Omnia audio processor. There, the main program is split into analog FM audio and MPS digital audio and processed separately. The analog and digital outputs of the Omnia are fed to the analog and digital inputs of the Embedded Exporter.

The Embedded Exporter and the quadcast data stream coming out of the T1 system from the Importer at the studio are connected to an Ethernet data switch along with the FlexStar HDx exciter. From the switch, all four HD Radio program channels flow into the exciter's Exgine where the analog and digital signals are converted into on-channel RF. The RF is then sent to the RF input of the HPX30 transmitter for final amplification.

Transmitter installation and setup

WJFK took advantage of a simultaneous power increase to coincide with the quadcast launch based on the new FCC guidelines that allow HD Radio broadcasters to raise power to -14dB. The station's existing transmitter was incapable of supporting the power increase, and software was not yet available for the existing Importer/Exporter to support four HD Radio channels.

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