Harris Field Service Engineer Walter Freeman (left) and WJFK Chief Engineer Jeff Loughridge turn on the transmitter for the first HD4 multicast transmitter tests.

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CBS Radio has a long history of HD Radio development and support. The company has been committed to digital radio since the early 1990s as one of three founding companies behind USA Digital Radio, the predecessor to iBiquity.

It makes perfect sense from this perspective that CBS Radio recently became the first broadcaster to launch an HD Radio quadcast — a four-channel HD Radio broadcast. WJFK-FM in Washington, DC, was selected as the station and is currently live with four HD Radio channels of mostly live sports talk programming.

The FAN Sports Network offers DC-area sports fans free access to WJFK-FM and signals from three other markets: WJZ-FM Baltimore (HD2), WFAN-AM New York (HD3) and WIP-AM Philadelphia (HD4). Dan Mason, president and CEO of CBS Radio, originated the concept of broadcasting the company's best sports talk programming from around the east coast in the DC market.

To make the concept a reality, WJFK established an IP-based distribution system to push signals from the three remote stations to its studios. WJFK also upgraded its transmission and STL systems to support four HD Radio channels, with a Harris HPX30 transmitter at the core. The overall system enables WJFK to broadcast a sports talk quadcast within the new FCC-approved power level of -14dB, expanding the reach of the HD Radio signals closer to the outer edges of the market.

Remote signal delivery

WJFK studios were initially picking up the three remote signals via each station's online radio stream. The station is implementing an IP-based distribution system to send fully packaged audio programs from the remote stations direct to WJFK studios.

The point-to-point configuration for each remote station includes Barix Instreamer and Exstreamer devices. The Instreamers encode the live signals at the remote stations for streaming over the corporate CBS WAN. The Exstreamers receive and decode the signals at WJFK, and an SAS 32KD audio router picks up the signal for delivery to a Harris FlexStar HDI-100 Importer.

While this configuration is active for all live sports talk programming, the stations occasionally have to switch to alternative programming featuring familiar station talent and shows, as WJFK does not retain rights to broadcast most out-of-market sports games.

Multicast generation

The WJFK system is a somewhat typical HD Radio common amplification transmission configuration. The Harris FlexStar Importer is the first step in generating the HD Radio quadcast. The Importer receives the three HD Radio multicast programs, HD2, HD3 and HD4, as AES audio, where they are compressed, encoded and multiplexed along with the PSD (program service data), into a single IP stream for transport over a T1 link to the Exporter.

WJFK installed FlexStar Importer version 4.3, which integrates core code from iBiquity. This new software code adds a third HD Radio codec to provide HD4 channel capability. An additional configuration was added through the Importer's Administrator application to provide an HD4 channel configuration onto the P3 carrier partition using the MP3 Extended Hybrid mode. An additional Audio Capture Client was also added to the Importer suite to intake the third audio channel.

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