WJFK-FM Launches HD Radio Quadcast

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CBS Market Chief Engineer Jeff Loughridge, Regional Director of Engineering Erich Steinnagel and SVP of Engineering Glynn Walden at the official HD4 launch.

CBS Market Chief Engineer Jeff Loughridge, Regional Director of Engineering Erich Steinnagel and SVP of Engineering Glynn Walden at the official HD4 launch.

The HPX30 transmitter was chosen as it was capable of generating the analog and digital power level needed for WJFK to operate at -14dBc while meeting the 6dB tighter out-of-band emissions requirements established for stations operating at elevated HD Radio power.

Setting up for the -14dB elevated sideband level was relatively easy and straightforward. The level was set up over the GUI screen of the exciter, and the integrated RTAC pre-distortion circuitry automatically made the necessary linearity corrections.

In sizing the output power requirements for the transmitter, it was necessary to account for the additional peak power requirements imposed by the additional Extended Hybrid (MP3 mode) P3 carriers. Using common amplification, the transmitter needed to deliver 13kW of analog power and 621W of digital power to the antenna (which needed no adjustments). That is about 6 percent more digital power than would be required by MP1 mode — well within the capabilities of the HPX30 transmitter. There is also plenty of headroom to raise the HD Radio injection to as high as -10dB if needed in the future.

Signal flow diagram of the WJFK quadcast

Signal flow diagram of the WJFK quadcast. Click image to enlarge.

The entire installation project took less than a week. The transmitter was delivered on a Monday morning to the rigger and to the site on Tuesday morning. The electrical work was performed Tuesday night, and on Wednesday the team connected the Burk remote control and finalized the RF plumbing. The dummy load tests were performed Thursday morning, and the quadcast went on the air that afternoon.

After a weekend of monitoring the system and a brief dark period, the official launch was announced the following week. Harris Field Service Engineer Walter Freeman and Transmission Product Development Manager Tim Anderson were on site to provide assistance throughout the installation and launch. At press time the HD Radio quadcast and supporting technology are both operating flawlessly.

Equipment List

Barix Instreamer and Extstreamer
Black Box LR0301A-KIT
DTS Neural Codec Preconditioner
Harris HPX30, Flexstar HDI-100, Flexstar HDE-200, Flexstar HDE-100
Moseley Starlink, Lanlink
Burk remote control

Walden is SVP engineering, CBS Radio. Loughridge is market director of engineering, CBS Radio, Washington DC.

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