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.
How long had this problem been going on ? It sounds like others had been tasked to find the cause prior to your visit. Do you know how many techs had failed to notice the broken legs ? Of course it is always best to investigate the problem while it is occuring, if possible.
This is a great example of how a technical problem can be caused by something as simple as checking out the physical environment: broken tower legs + a strong directional wind = no coverage. It reminded me of the freight train that interfered with the cellphone signal.
I don't know how long that had been a problem. I got the impression that it was just that spring. This was one of those 'it can't happen' things that Mr. Agan's talks about in his book. It also illustrates a couple of his points, 'understand the system' and 'quit thinking and look'.
I agree Ann - so many times people do everything except go and take a look...funny how the most obvious task is usually skipped as people look for more exotic reasons for a failure. It also speaks of the importance of environmental factors on equipment and that it should always be a design consideration whenever possible. Better to have more rugged tower legs in the first place...and avoid the problem completely.
Working for a radio service company so you know heights are involved and there is an elevator - I'm guessing the prior techs did not have much initiative...they sent the "new guy" when it seems more logical to send an experienced tech on that equipment with the new guy. I could be wrong but it looks more like a work culture issue than an inaccessibility issue...
I apologize Jake - I did not mean to imply it is a "walk in the park." My point was only that I would never apply for that type of job because if going up that tower was in the job description - I would be scared to death! But visual inspections are important and a part of any technical job. I guess I am thinking that different people have different personalities and heart stopping heights are a part of that field so it is something people in that field do. As far as seniors - of course I agree. But again, that is a work culture - youngsters doing that type of work is traditional and should be. Seniors have earned a pass. But experience does not necessarily mean senior - No offense intended!
Nancy, I'm always surprised when in a group of people discussing what to do about a problem with a structure or a machine and most of them want to theorize about possible problems/solutions or wave their arms trying to describe the problem instead of going and looking at it. That sometimes includes engineers, I'm sorry to say. Good point about the tower legs design--why weren't they tested in/designed for high winds?
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