Broadcast Writer

By Vicki W. Kipp
Society of Broadcast Engineers (SBE) Chapter 24 Newsletter
July 1, 2004

WHIT-FM 93.1 MHz “The Lake” may feature a timeless rock format, but their sign-on was almost eight years in the making. WHIT is the seventh Madison station owned by Mid-West Management, Inc. WHIT-FM has its studio at 2740 Ski Lane in Madison. The new radio station began transmitting test signals and TV show theme songs in mid-July. Deforest, Wisconsin is the city of license for this six-kilowatt FM station.

Planning

The tower and antenna were designed and constructed by Warmus and Associates from Cleveland, Ohio, in conjunction with Carl E. Smith Consulting Engineers radio engineering firm.

Issues

When the FCC approved Mid-West Management, Inc.’s license application in 1996, the station expected to be on the air in 1997 or 1998. Finding an acceptable tower site was the greatest concern. “The time involved in this project is the most significant issue,” says Mid-West Management, Inc.’s Director of Engineering, John Bauer. The biggest roadblock to finding a workable tower site was that WHIT’s city of license, DeForest, limited the possible tower sites to an area that is used for aircraft traffic.

Mid-West Management, Inc. first approached the FAA with possible tower sites, but this effort turned out badly. Luckily, the broadcasters fared much better when they first worked with the Dane County Airport on site selection, and then dealt with the FAA. The Dane County Airport authorities were straight forward in telling Mid-West Management, Inc. which sites would or would not work. Vertical detuning skirts are attached, allowing placement close to the AM array.

An acceptable tower site was found near the intersection of Bailey Road and Bird Street in Sun Prairie in the center of Christian radio station WNWC 1190 AM’s antenna array (Figure 1). Once the Sun Prairie tower site was chosen, there were more matters to be considered. The tower’s location within a low-grade wet land meant that environmental issues had to be accommodated. Aside from that, locating an FM tower in the middle of an AM array raised some RF issues. For WNWC’s pattern to be acceptable, the WHIT-FM tower was not to have more than one Watt of re-rated energy coming off of it. When the tower construction was complete, an AM Reproof was performed to verify that detuning efforts on the WHIT tower were adequate to restore WNWC’s AM coverage pattern to what it was before WHIT’s tower went up.

For proper detuning, it is critical to repeat the phase angle and ratio between the two detuning networks. WHIT-FM will soon permanently install an AM antenna monitor to keep skirt detuning in proper order.

Transmitter

When operating at full power, WHIT will transmit 5.5 kW ERP from their Nautel FM-8 solid-state transmitter. The transmitter is housed in a Trachte Building.

Tower

The guyed PiRod tower measures 317 feet tall, but reaches 320 feet tall with appurtenances. The WHIT tower is striped in maritime white and aviation orange, and is lit with medium strobes during the day and red beacons at night. Guy wire composition was a big deal because the guy wires must not affect the radiation from the AM array surrounding WHIT’s tower. The tower is steadied by very light-weight but strong electrically-transparent Phillystran Kevlar guy wires with a copolymer coating. Guy wire insulators are not needed for Phillystran guys because the line is completely isolated. The tower is adorned with multiple detuning skirts (Figure 2) to deal with the AM transmission in close proximity. To meet Dane County tower co-location zoning criteria, the WHIT tower has space reserved in the middle of the tower for two cellular antennas.

Antenna

The two-bay directional Jampro JMPC-2R antenna bays are covered by radomes. Parasitic reflector elements behind the antennas are in place to protect Milwaukee FM station WJZI. WHIT provides city grade coverage in their city of license, Deforest, and also covers Madison and other high-population areas in Dane, and parts of Rock, Jefferson, and Columbia counties.

Welcome to the skyline, WHIT-FM!

Figure 1. WHIT-FM tower(right) located adjacent to the WNWC-AM antenna array.

Figure 2. WHIT-FM tower, with radomes, reflectors, and STL near the top.