The coming of HD Radio to WKSU

April 8, 2014


began in 1991 on a tour bus in Las Vegas.
Facility Showcase, Jan 2010

It was a balmy April afternoon in Las Vegas when I boarded the bus in 1991 for a tour through the city. No, it was not a sightseeing trip but rather a drive around town to listen to a DAB FM test station. Each seat on the bus had a set of headphones and an A-B switch. Switch position A provided the analog audio side of the broadcast and position B presented the latest and greatest in digital FM broadcast technology — clean, noise-free, high-fidelity program audio. The difference between the low-power test transmitter's analog broadcast and its DAB signal was highly impressive — especially when the analog signal went into noise and the stereo image collapsed. It was on that balmy Las Vegas afternoon that I first caught the vision for just how much FM broadcast audio might be improved. I have never lost focus of that vision.

We now fast forward through many years of hopes, dreams, and promises made by DAB and IBOC technology developers to the present day adoption of in-band on-channel (IBOC) AM and FM broadcast technology as the U.S. standard. Like so many stations across the country over time, WKSU's management team has maintained a close watch on the development of IBOC technology, its potential benefits, costs, and perhaps turning out to be the most important, the timing of its availability in relation to other competing listening technologies including satellite and Internet radio.

Going digital

Repeater station WKRW has the 1992 installed analog Harris transmitter and the new IBOC transmission equipment behind.

Repeater station WKRW has the 1992 installed analog Harris transmitter and the new IBOC transmission equipment behind.

In 2003, WKSU chose to construct its fourth FM repeater station, a 4kW facility located in north central Ohio. Via grant funding provided from federal and state government agencies, a decision was made to have this repeater station, WNRK, become the first IBOC broadcast facility within the WKSU network of stations. The station went on the air in 2004 using a Harris Z hybrid transmitter to provide an analog and IBOC HD-1 signal. Audio delivery to the site at that time was by a high-quality FM tuner receiving the WKSU analog signal for rebroadcast.

WKSU management continued monitoring IBOC technology progress, implementation across the country, receiver availability and market penetration. Questions about its benefits to the station's public radio operation began to rise — especially regarding the potential costs required to bring the entire network of stations (five full power and two translators) up to IBOC capable standards.

In 2005, with assistance from a grant received from the Corporation for Public Broadcasting (CPB), the opportunity came to add an IBOC signal to WKSU. That led to more questions as to what method of IBOC transmission technology to use. Our broadcast engineering team settled on a Harris Split-level system that required the addition of a Harris Z transmitter, a Dielectric RF combiner, a reject load, and all of the related RF plumbing. Fortunately, the WKSU transmitter building was large enough to accommodate the additional equipment including sufficient electrical and ventilation systems. The Split-level system was successfully added to WKSU's Broadcast Electronics FM-20T analog transmission system. At that time, program audio delivery to the site from WKSU's Broadcast Center located 13 miles away on the main campus of Kent State University in Kent, OH, was via a Harris CD microwave link with an Intraplex T-1 delivery system backup. Both systems were limited to 15kHz high frequency response so WKSU's HD-1 signal was on the air but not yet with a full 20kHz audio signal for use on the IBOC signal.

Broadcast Electronics FMi-1405 IBOC transmitter and associated equipment at repeater station WKSV

Broadcast Electronics FMi-1405 IBOC transmitter and associated equipment at repeater station WKSV

As the journey continues through time, the fast-forward button takes us to the year 2008. WKSU had a major decision to make. Either add 5,000 square feet onto the Broadcast Center building or complete the installation of IBOC technology at its non-IBOC stations and further enhance the network with the implementation of multicast channel and program associated data (PAD) capabilities for each station. As station management faced the launch of a capital campaign, a professional firm was retained to conduct a feasibility study with potential significant donors for purposes of determining which project they would be more likely to endorse. Surprisingly, the wants, needs and demands for more “channels” — both via broadcast and Internet — won out. The quiet phase of a digital conversion capital campaign was launched and a commitment to have a complete IBOC/multicast, PAD-capable network was made.

The WKSU network of stations, Ohio's largest combined FM radio signal, collectively reaches a widely diverse audience throughout all or part of 22 counties in northeast and north central Ohio. Nearly four-million persons reside in the region that ranges from densely populated urban areas to rural, agriculturally oriented communities. The need to provide programming of significant value to a diverse audience led to a design goal of being able to program the analog and all digital channels of each of the five full-power stations (main and four repeater stations) independently with origination occurring at the Broadcast Center. With the help of generous capital campaign contributors and multiple grants received from the Corporation for Public Broadcasting, the WKSU total IBOC commitment was launched and the multi-channel centralcasting concept design undertaken.

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began in 1991 on a tour bus in Las Vegas.
Facility Showcase, Jan 2010

Accepting the challenge

Challenge number one was how to get the analog, RBDS and the IBOC data stream (HD-1, HD-2, HD-3 and PAD) to each transmission facility. Terrain limitations, tower loading issues, and overall costs quickly eliminated the possible use of a microwave network. Ku band satellite delivery became a brief consideration; however, the northeast Ohio climate does not favor reliable Ku signal delivery. Internet delivery was not an option because of compression, timing and many other issues inherent with the Internet. Thought then turned to the use of T-1 lines. Through a special relationship with Kent State University and the state of Ohio, WKSU was able to obtain a T-1 line to each transmitter site with all lines originating from the Broadcast Center at a total cost that was the same or somewhat less than what monthly satellite delivered bandwidth costs would have been. With design assistance provided by Broadcast Electronics in conjunction with WKSU's IT department, an STL-IP delivery system was developed using the Audio TX by MDO-UK equipment along with Cisco Systems routers and switches. In addition, the STL from the Broadcast Center to WKSU's transmitter site now includes a Mosley Starlink microwave system that operates parallel to the STL-IP T-1 line delivered system with automatic switchover in the event of either path's failure. The new STL systems provide full 20kHz audio.

Flagship station WKSU's analog equipment row on the left and its Harris Z model IBOC transmitter on the right across from a Broadcast Electronics FM-20T analog transmitter installed in 1997.

Flagship station WKSU's analog equipment row on the left and its Harris Z model IBOC transmitter on the right across from a Broadcast Electronics FM-20T analog transmitter installed in 1997.

Next came the need to upgrade the analog transmitters at repeater stations WKRJ, WKRW, and WKSV. Based on power level requirements and costs, the Broadcast Electronics model FMi-301 solid-state transmitter was chosen for WKRJ, an FMi-201 for WKRW, and an FMi-1405 dual-cabinet system for WKSV. Ventilation system upgrades also had to be made at each of those stations because of the increased IBOC transmitter heat output. The existing analog transmitters at WKRJ and WKRW became standby units with the installation of a motorized RF switch for easy remote transmitter selection when required. While WKSV already had a standby transmitter, the main transmitter, a CCA FM-12,000, had to be removed from the Rohn 12' × 18' prefab building to make room for the new transmitter. The arranged logistics provided for the removal of the CCA transmitter first thing in the morning and the placement of the new transmitter that same morning. Broadcast Electronics model FXi-250 exciters were installed with each new transmitter. The WKRJ and WKRW projects took place in late May/early June of 2009 and the WKSV project was completed in July of 2009. Prior to these projects, the exciters at the 2004 constructed WNRK repeater station and at WKSU's transmitter site were upgraded to a Broadcast Electronics exciter model FXi-60 (WKSU in July of 2008 and WNRK in January 2009) to enable the broadcast of the IBOC stream. Broadcast Electronics RDi-20 accelerated RBDS generators were also installed at each transmitter location for broadcast of RBDS on the analog side.

To facilitate the independent multicast program distribution to each station, five Broadcast Electronics model IDi-20 importers and five model XPi-10 exporters were installed in the Broadcast Center's master control room — a set for each station. Additionally, five Orban 8500HD units for audio processing of the analog and HD-1 channels were installed in the newly placed master control room rack cabinets (seven new cabinets that include 30 Arbitron PPM encoders plus four existing cabinets). A Neural multi-channel audio processing system is utilized to establish the audio quality for the HD-2 and HD-3 channels. Audio sourcing and routing is largely managed by an Enco automated program delivery system (soon to be updated to all linear storage) along with the use of multiple Axia Livewire audio nodes. PAD and RBDS information is handled by a Broadcast Electronics TRE message managing system for each station. Monitoring of each transmission facility is accomplished via existing remote control systems operating in ATS mode and an on-site Audemat Golden Eagle HD monitor at each station — all networked for remote monitoring — along with Day Sequerra model M4 HD tuners.

Regional awareness and popularity is growing for WKSU's globally accepted folk music channel (Folkalley.com) broadcast on the HD-2 stream and an all-classical music offering on the HD-3 channel. During WKSU's recent fall fund drive the station placed 589 HD capable radios in the hands of donors who pledged at the $180 level. Generous underwriting friends of the station provided those radios at no charge to WKSU. WKSU's HD-3 all classical stream is also heard over Cleveland's WNWV HD-3 channel by special agreement between the two stations. The station will continue promotion of HD Radio to the region and has received a grant from CPB to develop an HD-4 channel with cooperation from Ibiquity Digital and Broadcast Electronics. Existing Broadcast Electronics exciters and importers are to be upgraded by special arrangement from BE when the product becomes available. Pending IBOC signal power increases are to be addressed on a station-by-station basis if and when approved by the FCC.

A close up view of WKSU's split level IBOC combining system and main/standby antenna switch.

A close up view of WKSU's split level IBOC combining system and main/standby antenna switch.

WKSU's in-house IT staff of Chuck Poulton and Dan Kuznicki, both of whom have excellent broadcast background, played a pivotal role in the development of this system and continue to work hand-in-hand with my long-time assistant Bob Kruppenbacher and myself in maintaining our extensive IBOC/HD Radio broadcast system. And, it should be noted that this very large long-term project would not have been possible without the fund raising expertise of WKSU's Executive Director and General Manager Allen Bartholet and his development associate Pamela Anderson along with the splendid cooperation that we received from both the WKSU and Kent State University business offices.

It has been many years since I rode the bus on that balmy April day in Las Vegas and wore the required badge that gave me passage onto the bus. The badge reads, DAB '91 Demo. I have that badge on my office bulletin board and glance at it at least once each day just to remind me that what happens in Vegas doesn't necessarily stay in Vegas.


Equipment list

Audemat Golden Eagle HD/FM
Audio Science 6585
Axia Livewire AES/EBU audio node
Barix Exstreamer 1000
Belar RFA-4
Bird Electronic 3129 BPM, BPME1-VM, BPME3-VM
Broadcast Electronics FMI-1405, FMI-201, FMI-301, FXI-250, FXI-60, IBOC rack cabinets, IDI-20, RDI-20, TRE Message Manager, XPI-10
Day Sequerra M2.2R, M4.2 R
Dielectric R101873025
MDO UK Audio TX
Moseley Starlink SL9003-4SLAN
Neural Audio Neustar SW4.0
Omnia One
Orban 8500FM


Bartlebaugh is director of broadcast engineering, the WKSU Stations, Kent State University, Kent, OH.



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