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Engineering Extra
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The Reference Room
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Workbench
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| Deedleheads Are Wiry & Scrappy |
| Also, How a Rain Drop Can Take Your Station Down |
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by John Bisset,
1.02.2008
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John Bisset has worked as a chief engineer and contract engineer for four decades. He is the northeast regional sales manager for Broadcast Electronics and in 2007 received the SBE’s Educator of the Year Award. Reach him at (571) 217-9386 or jbisset@bdcast.com. Faxed submissions can be sent to (603) 472-4944. Submissions for this column are encouraged and qualify for SBE recertification credit.
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Al Peterson writes that when studio construction was completed some months ago at the new Radio America Network facility in Arlington, Va., engineers were left with hundreds of useless little wire scraps and cable ends everywhere.
Too small to actually work for anything, yet so many that no one felt right to just throw them away. Thus was born the “Deedlehead” desktop mascot.
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Fig. 1: The Deedleheads.
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This collection of 25-pair CAT-5 Deedleheads lives on the desktop of Meg Buenting, a producer for the network’s syndicated “Greg Knapp Show.” Among her mascots are a cigar-chomping tough guy with a military haircut, a circus clown and a white-haired mad professor, the only Deedlehead with arms and a headband. Some of the mascots are shown in Fig. 1.
The name was more or less coined by Buenting. During studio construction, she helped chase down dozens of wire pairs with an inductive signal tracer, and became adept at listening for the characteristic two-tone deedle-deedle when the probe was jammed deep into cable bundles.
The act of signal tracing became informally known as “deedling” during the buildout, and the name eventually worked its way to the mascots.
Every now and again on a Monday morning, a new Deedlehead may appear on Buenting’s desk, depending on how bored or creative the engineering staff was feeling over the weekend. Make your own and send me a photo to jbisset@bdcast.com, and we’ll publish it.
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Paul Sagi in Kuala Lumpur reminds us to be cautious in using nail polish remover to remove permanent marker from coils or components. The liquid usually contains acetone, which can damage plastic parts.
An alternative is correction fluid thinner, but again, caution around plastic supports or spacers. Some plastics can withstand it, and Paul has used correction fluid thinner to remove permanent marks from equipment.
He adds that it should go without saying to use solvents in a well-ventilated area away from sources of ignition.
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Fig. 2: A rain drop prepares to take a station down.
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Paul had a situation where he needed to get the speaker wires across a ceiling, from one side of the room to another. He removed some ceiling tiles and used a bow and arrow to carry a string above the dropped ceiling.
If you’re not a bowhunter, another choice is to secure a large bolt or dud transformer to the string and throw it. I’ve tried that method, and it seems the bolt always gets stuck on either the pipes or supporting ceiling hangers. It works, but removing all the extra ceiling tiles is time-consuming.
There’s one other method that I’ve not tried, but I understand it works well. Borrow your child’s remote-controlled car or truck. Tie a string to the rear bumper and let it run over the ceiling tiles to the other end of the room. The trucks with the big wheels navigate over the tile supports nicely, and the radio controller allows you to dodge pipes or support wires. Write to me if you’ve done this.
Once the string reached the ceiling/wall junction, Paul needed to run the cable down the wall to a patch panel. This posed a difficulty, as the wall was filled by dense fiberglass. The fiberglass resisted his poking the wires, and then a broom handle, through it.
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Fig. 3: The incorrectly mounted Austin Ring Transformer.
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Paul’s solution was to take a chain about 10 feet long, made of welded links of 3/8-inch thick steel, and tie the wires to it. He dropped the chain into the void between the studs over the patch panel opening. The heavy chain ripped through the fiberglass and carried the wires to the patch panel opening.
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Stuart Engelke is the engineering manager for New York AM stations WWDJ and WMCA. A new Austin ring transformer was installed at one of his towers, and during the next rain, the station kept getting transmitter VSWR trips.
The Austin ring transformer is a method of coupling voltage for tower lights across the base of a series-fed or “hot” AM tower. This method is more commonly used for higher-power (50 kW) stations.
The reason for the VSWR trips? Take a look at Fig. 2. The contractor installed the transformer with the arc gap balls above and below each other. Each drop of rain briefly shorted the tower, causing the VSWR trip.
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Fig. 4: An example of the focused LED beacon as it bathes a transmitter room.
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Fig. 3 shows complete view of the improperly installed transformer. A couple of wrenches fixed the problem — with the station off the air, of course.
Stuart’s project included a new LED beacon assembly. The beacon output can be seen eerily illuminating the phasors of the transmitter room in Fig. 4.
What is interesting is the narrow beam of light — hard to see from the ground, directly under the tower, but very bright from a mile away, as the light beam is focused.
Austin Insulators provides a range of base and guy insulators, as well as the Austin ring isolation transformers that Stuart used. Head to the site at www.austin-insulators.com/radio/product.html for more information.
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