(click thumbnail)Fig. 1: Rust can form anywhere on a tower.We've heard the phrase "out of sight, out of mind." Sometimes it refers to an abandoned AM site no one has time to visit. The tower field is a forest, air filters are clogged, rodents and insects have taken over the ATUs ...
And then there's the rusting tower.
Fig. 1 is almost unbelievable, isn't it? Up in the air, only the crows are wise to the problem.
Michael Millard from South Florida sends the picture, taken in his days as vice president of operations and engineering for Pinnacle Broadcasting. Seems Michael's group acquired a 1,400-foot tower of unknown manufacture. A little detective work revealed that the tower had been installed in the Carolinas but later moved to Texas.
The tower was reinstalled incorrectly, with some sections in the wrong places and with questionable hardware - all of which Pinnacle had to correct, for DTV deployments. It acquired the property long after the rebuild.
(click thumbnail)Fig. 2: Don't let coaxial cables obstruct the red and white painted tower legs.
By the way, like many readers, Michael scored 100 percent on identifying the tower problems we've shown in previous columns. He adds that for extra credit, you should count the transmission lines that are required to be painted, depending upon which FAA Advisory Circular the tower was FCC-registered to (Fig. 2, above).
Thanks to Michael for sharing another reason engineers should visit transmitter sites and why the tower needs to be climbed and inspected, top to bottom.
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Eric Hoehn works for XM Satellite Radio and was instrumental in coordinating EAS activity in the Washington market. He still monitors EAS issues and passes along this item from Gary Timm, state coordinator for EAS in Wisconsin.
(click thumbnail)Fig. 3: On most solid-state transmitters, critical backup settings are kept 'alive' with a backup battery. Make sure it's fresh.
If you own a Sage Endec and haven't replaced your backup battery yet, it may be dying soon. Gary received a call from a Sage user with the date stuck on 1/1/95 and a start-up message "Time is bad." Replacing the battery fixed the problem. You'll find the instructions in the Sage owner's manual. Act now before you're blindsided.
If you're replacing batteries, don't forget the ones inside your transmitter controllers. On at least one brand, if the battery dies and the transmitter shuts off - say, due to a power failure or lightning strike - the transmitter will not remember the power level, and defaults to "0" watts.
After scratching your head awhile and then hitting the Raise Power button, everything returns to normal - until the next power failure.
I made it a practice to replace all batteries twice a year, when we were also setting our clocks forward or back an hour. Used batteries were recycled into my family's toys so they weren't wasted.
Don't forget the smoke detectors.
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Paul Sagi hails from the States but married a Malaysian physician and has transplanted to the Far East. He has enjoyed 27 years in electronics and now works in a radio complex of 27 studios housing seven FM stations, nine satellite stations and production facilities. Paul sends several tips.
The first is the most convenient yet inexpensive source of compressed air you will find. For removing dust Paul uses a sauce bottle, the kind of plastic squeeze bottle that restaurants use for ketchup.
To improve the sealing of the bottle, Paul coats the threads and top of the bottle with a little bit of silicone grease.
A quick squeeze gives a strong puff of air. A paint brush used at the same time helps with stubborn dirt. Paul cautions us to use a face mask and goggles; the jet of air is powerful.
Do you know why you shouldn't use the squeeze bottle around high voltage? That dust cloud is conductive.
Here's a great tip for a contract engineer or tower rigger. One way to find air leaks is by the ultrasound they create. Paul advises that there are commercially available detectors to hear them.
Speaking of tracking down noises, do you know a nurse or doctor? Ask if you can obtain one of their old stethoscopes. Pinpointing funny noises inside a transmitter, or a car engine for that matter, is a snap with such a directional listening device. (Editor Paul McLane adds that you might also get more respect from your co-workers if you walk around the station wearing the thing.)
In the Feb. 1, 2003, Workbench we wrote about the "very high static voltages that can develop across the base insulator of a tower, even with clear blue skies. All that's
needed is a little wind and relatively dry air. The conditions will produce a pretty good jolt for no apparent reason."
Paul Sagi suggests using a discharge/grounding stick to ensure the tower is grounded, before applying the battery jumper cable to ground.
His studios use a lot of DAT machines. Sometimes he finds that oxide deposits on the
capstans adhere too firmly to be removed by the usual solvents. In such cases, he uses a narrow brass strip to scrape off the oxide. The brass is hard enough for the purpose but soft enough not to damage the capstan.
Now that Flash memory sticks or pen drives are so inexpensive, Paul attaches one to his company ID tag. The memory stick contains telephone numbers, useful information on equipment, useful Web sites, a DSP book and other electronics data. He only needs to insert the pen drive in a USB port of a PC to access the information.
Reach Paul Sagi at email@example.com.
Submissions for this column are encouraged, and qualify for SBE recertification credit.