Radio Kansas Rebuilds for its RF Future

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KHCC: another angle on the RF plumbing

KHCC: another angle on the RF plumbing

Together, via 6dB ERI combiners, the systems deliver the required elevated digital signals to the existing antennas. For example, the KHCC system runs the HPX40 at 13,230W of FM power and 1,670W of HD Radio power. Combined with the Z16HD+ at 7,000W of FM power through a 6dB combiner, the resulting TPO is 20kW analog and 1,252W digital - equal to the full-licensed FM power and -12dBc HD Radio power. This combination minimizes transmitter power consumption, reject load power and cooling requirements.

HD+FM architecture

The three transmitter sites almost form a perfect triangle, with distances of about 90 miles between each tower. The delivery architecture from studio to transmitter sites is also a bit unusual, employing two-hop microwave paths from the flagship site (KHCC) to the distant tower sites.

At the studios, the main program audio comes from the main studio console; automation delivers HD2 program audio. Both are processed with Aphex Compellers for mild control and limiting. A Moseley StarLink microwave STL system carries the main program AES audio to the KHCC site, with a Harris Intraplex STL running over a 5.7GHz radio carrying HD2 program audio and high-speed data. Main program audio feeds an Omnia.6 on-air audio processor at the transmitter site, while the HD2 audio is fed directly to a Harris FlexStar HDE100 Importer.

KHCC: HPX40 that will be partitioned off from the room to allow ventilation of the cavity from behind. This will cut cooling requirements drastically.

KHCC: HPX40 that will be partitioned off from the room to allow ventilation of the cavity from behind. This will cut cooling requirements drastically.

Our HD Radio architecture uses a single Harris HDE100 Exporter for all three stations. The main program audio from the Omnia hits the Exporter, which outputs delayed FM audio and creates the UDP signal consisting of HD1, HD2 and associated program data (PSD). The UDP signal is distributed to the local and distant exciters through a Cisco switch and the data channel on the StarLink-based microwave radios. The main FM program audio remains in the AES format and is distributed similarly.

The FlexStar exciter is an amazing piece of machinery considering the way it simultaneously drives two transmitters. In the old split-level setup, the exciter's main 55W output fed the legacy, FM-only transmitters. The auxiliary 10mW output handed off to a FlexStar BoostPro amplifier mounted in the Z transmitter. This was a nice textbook setup for additional power that worked very well.

The enhanced split-level configuration changed things around. The main 55W exciter output now feeds the Z-Series transmitters at each site, while the 10mW output feeds a BoostPro in each HPX.

The BoostPro is essentially a highly intelligent second power amplifier for the exciter. The reason for the change rests on the Flexstar exciter's output port limitations that allow FM+HD from the auxiliary spigot when FM-only is selected on the main 55W output. The HPX and BoostPro have not yet been used together in the field, so specially-designed BoostPro configurations allow the HPX to recognize the BoostPro correctly as an exciter power amplifier - making Radio Kansas the first broadcaster to use the two components together.

- continued on page 5

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