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Long Saga Comes to a Happy EndingKUSI's Trial By Fire By Gary Stigall Richard Large, Chief Engineer at KUSI likes understatement when describing the massive difficulties facing them this year. "The Dielectric antenna that was installed in January would not handle the licensed power of our transmitter." Apparently, rather than a center-fed design as is often the norm for a high-power array like KUSI's, all the power was fed, and thereby concentrated, in the bottom. Richard says that meant "arcing, burnt slot covers and flames." That sort of thing. "After tests, modifications and more testing, Dielectric agreed that the antenna was poorly designed and would not handle our licensed power. They agreed to build a replacement. "Eight months later, after many discussions with Dielectric over the antenna design, possible modifications, testing and tuning, our new antenna arrived in San Diego, ready for the short trip up Mt. San Miguel. "The antenna was transferred from the large semi-tractor and trailer over to a short truck and trailer to negotiate the many turns up the mountain. After traveling 3500 miles to San Diego, on the last turn up the mountain one of the antenna climbing pegs found the chain link fence and grabbed hold. The antenna was pulled back and off its mounts, falling onto the trailer, damaging numerous radiating elements, the Teflon pressurized radome, fiberglass strips and support hardware. "After inspecting the antenna, it was decided that we would make corrections on site and we replaced all damaged hardware ourselves." Then up went the antenna. All Systems GoAll connected, they fired up the transmitter and switched to the new array. The VSWR relays tripped. It couldn't handle full power. After several tries raising the power, it eventually wouldn't top even 10% without protest. They eventually powered down and dismantled connectors, inspecting the antenna and feed waveguide until they found the culprit: a rag left by Dielectric workers in the input tuning section of the antenna. Says Richard, "The antenna has been reinstalled and is working fine. Our field strength study indicated a 3db improvement in signal strength in most areas of San Diego. I can say that Dielectric does stand behind their product." A note to other users of Mt. Miguel:"When large vehicles with trailers or cranes negotiate the mountain, most have a vehicle following them. When they see a potential problem they blast their horn to warn the drive. This does not work. They need two-way radios so they can be in direct contact at all time. "Also, cranes and power poles don't mix well. Bragg Crane Service on the way up Mt. Miguel managed to snag the guy cables on a SDG&E power pole. The support pole was scattered and one of the cables affixed itself to the crane. Power was lost on the mountain for several hours. Two-way radio communications between the driver and chase vehicle was requested. Someone else assumed they had it. It turned out they did not. We will either personally check or supply radios in the future." |
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