Station Upgrade: KEXS

November 28, 2011


KEXS is licensed to Excelsior Springs, MO, a community about 25 miles northeast of Kansas City. The station has operated for more than 30 years from a transmitter site located at the studio building. This 1kW, non-directional daytime signal covers most of the Kansas City metro, but the licensee, the Catholic Radio Network, wanted to increase its coverage to serve all the metro. Thus, it began to investigate the possibilities.

Adding more towers on the small existing site presented some challenges. While the station operated a two-tower array on the site many years ago, the possibility of installing a three-tower array was not feasible.

The transmitter, rack and phasor are mounted on a 4

The transmitter, rack and phasor are mounted on a 4" stud to provide just a little extra clearance.

A new tower site was inevitable. Early in the process, a site was found, and the plans were drawn to install a tower with folded unipole skirts. But, the unipole approach was quickly abandoned in favor of a simpler radiator; likewise, the search for a suitable piece of land continued. In time, a section of land was found about four miles south of the studio. Surrounded by farmland and away from the growth of the town, the new site would comfortably host three towers. There was just one problem: The land sits in a flood plain.

A stream runs along the back of the property, and on occasion, the low elevation suffers some flooding, but the site was still promising. It was a little closer to the Kansas City metro and had an easy line of site from the studio.

Reviewing the flood history in the area, it was noted that the highest the waters reached was four feet. This was taken into account for the construction design, and the towers and the transmitter building were mounted above ground level.

Reaching high

The coax exits the building through the floor and through two heavy conduits.

The coax exits the building through the floor and through two heavy conduits.

It's not uncommon to find elevated tower bases, but to see a transmitter building sitting on 9' stilts is rather unusual. The transmitter building, a prefabricated VP steel building, sits on four beams. Measuring about 24' × 16', the garage-door entrance is accessed by a staircase. Inside, the Phastek phasor and Broadcast Electronics AM10A transmitter are set in place on 4” tall wooden beams. The beams were added to provide just a little extra space in case of a severe flood.

While the main purpose of the elevated building is to safeguard against flooding, there is an added benefit: security. There are no blind spots around the building now. The ground system and coaxial cables are also buried. The coax leaves through the floor of the building and enters the ground through two heavy-wall conduits. A large conduit houses the radiating cables. A smaller one houses the antenna monitor cables.



Burying the cables. Photo by Ben Weiss

Burying the cables. Photo by Ben Weiss

Contract Engineer Ben Weiss, CPBE, oversaw the project. Weiss worked with Chris Kreger of RF Specialties of Missouri — based in nearby Kearney, MO — for the equipment. Kreger also offered his services to construct the site.

Because the field was used as farmland, there was little that needed to be done to prepare the land before construction could begin. Overall, Weiss says the project went like clockwork. All the materials and crews arrived on time, and even the weather cooperated in December 2008 and January 2009.

Work begins

After the building was raised, the transmitter, phasor and ATUs were lifted into the building with a fork lift. Once the towers were erected, the ATUs were moved from the transmitter building to the towers with a high loader. The towers themselves are top-loaded and use about ⅓ of the upper part of the guy wires to effectively create ¼-wave radiators. Rocky Mountain Tower erected the radiators.

Shiny, new components inside the phasor

Shiny, new components inside the phasor

Once all the equipment was installed, Charles A. Hecht, the consulting engineer, and Kurt Gorman of Phasetek arrived on site for the final tuning and system proof. Weiss says that step took about a week. A very short time later, the station had its FCC authorization to commence program transmission. The new KEXS site was on the air.

Currently operating at 3.4kW, the station plans to apply for a power increase to 7.5kW soon, which is why a 10kW transmitter was installed. Once the licensing is complete on the new facility, the station expects to authorize the non-directional site as a backup with a reduced power level from the previous 1kW.

The STL antenna is mounted on the building. The studio is only four miles away.

The STL antenna is mounted on the building. The studio is only four miles away.

The pattern looks like a loose hypercardioid pattern aimed at Kansas City. The nulls of the pattern result in a slight decrease in coverage in two nulls compared to the non-directional pattern, but the loss is minor.

While FM installations and HD Radio get most of the attention today, it's encouraging to see a station owner invest in a stand-alone AM signal. For KEXS, the attention to building a quality facility will help that station serve its devoted audience, and likely improve that audience because of the increased coverage area.



An ATU is moved from storage in the transmitter building to be taken to a tower base. Photo by Ben Weiss

An ATU is moved from storage in the transmitter building to be taken to a tower base. Photo by Ben Weiss

Chris Kreger of RF Specialties installs an ATU. Photo by Ben Weiss

Chris Kreger of RF Specialties installs an ATU. Photo by Ben Weiss

Map the sites

Studio: 39° 17' 39.00” N, 94° 15' 37.00” W

New site: 39° 17' 39.00” N, 94° 15' 37.00” W

One ATU installed. Photo by Ben Weiss

One ATU installed. Photo by Ben Weiss

The towers are up, the ATUs are installed and everything is ready to be tested. Photo by Ben Weiss

The towers are up, the ATUs are installed and everything is ready to be tested. Photo by Ben Weiss

Equipment List

Andrew Heliax LDF4-50A (0.5”), Heliax LDF6-50 (1.25”)

Broadcast Electronics AM10A

CRL MDF-400, PMC-450

Kathrein Scala PR-950 Paraflector

LEA International surge suppressor

Middle Atlantic rack

Phasetek phasor and ATUs

Potomac 1901

Sine Systems RAK1, RFC-1/B, RP-8

TFT Model 5195-M, Model 753

Station owner Jim O'Laughlin prepares to turn the transmitter on. Photo by Ben Weiss

Station owner Jim O'Laughlin prepares to turn the transmitter on. Photo by Ben Weiss

Tower Innovations towers

Varco Pruden Buildings steel building

RF Specialties of Missouri - dealer

Charles A. Hecht and Associates - consulting engineer


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