I once worked for Radio Service Company, the Motorola two-way radio shop in Lincoln, Neb. It had several repeater systems around the area, and at least one was installed on KOLN-TV's tower near Beaver Crossing. This was when there was an equipment shed mounted on the tower around 1,200 feet off the ground, gone now due to removing some of the load from the tower for DTV conversion.
Access was via a 20-minute elevator ride up the middle of the tower so we didn't have to climb it. Occasionally, the shop would get complaints from customers to the west that their radios didn't work. No complaints from the north, south, or east, however.
Since I was the new guy, I was asked to go look at it. Of course, the radio was good, and the SWR on the antenna was good, just as I was told to expect. The next thing I did was to take the elevator to where the antenna was and look at it. The antenna was fixed to an 8-inch triangular tower section mounted horizontally so that the vertical antenna was about 10 feet from the TV tower.
Two of the triangular tower section legs had broken about three feet back from the antenna mount. The slightest amount of wind from the west would cause the antenna to lean to the east. The coax lines for that and other low-gain antennas ran along one of the broken legs and limited the amount of twist in the tower section. Due to the narrow beam of the high-gain antenna, the customers to the west lost coverage when it leaned. After the shop's tower crew repaired the mount, all was well in the west again.
This entry was submitted by Stephen Wimmer and edited by Rob Spiegel.
Stephen Wimmer has held an amateur radio license since 1968 and a commercial radio license since 1970. He served in the US Navy for six years as a communication technician, and since then he has worked as an antenna design technician, a radio service technician, and currently as an electronic design technician for Bosch Security Systems in Lincoln, Neb.
Tell us your experience in solving a knotty engineering problem. Send stories to Rob Spiegel for Sherlock Ohms.
Our signals come from a 200 watt translator several miles away. When it rains, the signals deteriorate because of a large tree across the street in the line of sight of the antenna.
Darned if I know. Its effect seems to be worse on one channel than the other, but all are in the UHF 40-50 range and all digital. I have suspected that translator antenna might be flaky, but I'd have thought it would have been fixed if it were a problem. It used to be at a different location but I moved it since it looked into two trees in my yard on the other side of the house.
This is a retirement town though, so maybe they just think there is something wrong with their setup, or they are working with a better antenna than mine: a corner reflector that fell off the house in the a windstorm, then had a tree limb hit it when the neighbor was taking down his tree! I am afraid the mast still has a bit of a up tilt.
Reminds me of the time I went up a tuna boat mast to see why the VHF radio was only receiving signals from the boat tied up next to it. When I looked for the antenna, it wasn't even there. I guess a bird had hit it and it was weakened from the sun and sheared off.
Look before you leap. I could have spent hours checking out the radio when it was nothing more than the antenna- or lack thereof...
Rain fade and attenuation due to foliage are real, but are much more of a problem in the GHz region than around 650 MHz. I believe he said the channels were all digital, so if he has a marginal signal on a good day, maybe just a little bit more attenuation is enough to trip the all-or-nothing barrier.
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