Radio World Buyer’s Guide articles are intended to help readers understand why their colleagues chose particular products to solve various technical situations. This month’s articles focus on antennas, RF products and power protection.
“Time and unforeseen occurrence befall them all.”
Dave Hacker quotes scripture to describe the case of a 3 kW Class A station in Bolivar, Tenn. He said a typical, uneventful summer day was transformed into a tangled pile of steel, cable and antenna debris after a logging company backed a hauler truck into and over a guy anchor of FM station WMOD’s 260-foot tower.
A strategy was needed and quickly. Hacker, whose regular job is chief engineer for Forever Communications, was called upon to help WMOD as a contractor.
“Having good people at your disposal certainly makes the process of rebuilding much simpler, and that was where Ernie Oliver from American Antennas and Mike Phelps from SCMS helped immensely.”
Hacker has worked with both for years. “We kinda know what the other wants and expects.” Because the tower had crashed into and through the existing transmitter building, it was going to be a complete rebuild.
Hacker says West Tennessee is in one of those geographic zones where winter would be happy to give you a half inch of cold rain, a half inch of snow, or a half inch of ice.
“I’ve learned well that antennas may claim to tolerate a quarter-inch of ice without significant impact, but it’s just not the case.” He considers radomes essential in his area, and his preferred antenna for this type of station and situation is the Shively 6813 three-bay.
This was right around the time that American Amplifier Technologies was purchasing the Shively line from Howell Laboratories.
“I had zero experience with AAT and really knew nothing about them. Moving manufacturing from one side of the country to the other in my mind was a significant undertaking, given the state of logistics these days, and I couldn’t help but wonder if it would take time for them to get up to speed and glitches ironed out at the new location.”
Despite the aggressive timetable, he was delighted when the antenna arrived at the freight terminal, and even more so when he inspected the crate.
“Gone were cardboard boxes. An extremely robust framed wooden ‘vault’ sat in front of me. Even more surprising when I opened it was the engineering that had gone into preserving the structural integrity of the antenna during shipment — wonderfully thought out and well executed in every minute detail. Superb job, AAT.”
Another surprise was that the bays had been assembled onto their feedline mount sections. And the radomes had already been attached.
“Gone was the old pressure relief valve for purging the line and ensuring a future tower climb for replacement when it inevitably started leaking. Also absent was the two-plunger tuning section, which was easy enough to use but at times could be finicky.”
So up the tower it went. With all cables, connectors, ground kits attached and dressed, the moment of truth had arrived. To achieve 3 kW ERP with 1-5/8-inch line and an antenna power gain of 1.56 dB, the transmitter needed to operate at a TPO of around 2.4 kW.
“The power button on the new GatesAir FAX 3 was energized — fire in the hole — and instant gratification, with 2.4 kW forward, 0.9 reflected. POINT 9!” Hacker said he has not had an antenna of any brand tune so well out of the box with no intervention.
“Coverage is superlative for this little Class A, and everyone was happy at the end of the day and ready for beer. Are Shively antennas now even better? I couldn’t argue against it.”
