Fig. 1: That first step could be painful. Regular site inspections will identify such problems before they grow. In our Sept.1 issue, Tom Ray described how nesting bees (we’re told they were actually wasps) indirectly helped him diagnose a sampling line problem.
Tom was called to another station recently, specifically to the tuning building, where the phasor was located. See Fig. 1.
Although these hornets didn’t diagnose anything, they were guarding that step ladder diligently.
Tom points out that though the site is clean and orderly, this is the kind of problem that can occur when sites aren’t visited regularly. The picture is the perfect argument to present to a GM whose attitude is, "Why do you need to go to the transmitter?" Thanks Tom for helping us to make our case.
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Sunbury Broadcasting’s Director of Engineering Harry Bingaman is a frequent contributor to Workbench. He always has a new twist on solving a problem around the radio station.
Fig. 2: Convenience and bright light are both provided by an LED work lamp. His most recent "find" is pictured in Fig. 2. It’s a battery operated, rechargeable LED trouble lamp. Gone are the cords and the broken bulbs. Harry has outfitted his transmitter sites and tool boxes with these lamps, which for LEDs provide a lot of white light.
Harry writes that he is amazed at how far portable light technology has come. He remembers not too many years ago that portable lighting consisted of either a penlight (AA and AAA) flashlight or two-cell, four-cell, six-cell or lantern (6 Volt) flashlights. They were rather bulky but functional, with limited battery life. Then came the big Maglite, which reminds Harry more of a weapon than a light.
Nowadays, when you walk into an electrical distributor, there’s a whole shelf of LED technology flashlights. The LED trouble lamp is made by Exide and includes a wall-wart charger.
I imagine your first question is about battery life. Harry was working under a console recently; when he was done, he closed up but forgot his LED light. The next morning, the morning drive guy thought Harry had installed a light under the console. It had lasted all night, and through most of the morning.
These work and seemingly last forever. Harry notes the newer models have an LED flashlight built into the end.
If you’d like more information on these lamps, click on www.toolprice.com. From the category selection column on the left, select the last listing, "Work Lights." It’s the best $40 investment you’ll make.
After reading Buc Fitch’s Marti incandescent replacement trick, Harry also sent in a picture of his phasor LED lighting.
Fig. 3: Broken filaments are eliminated by converting to LEDs for these phasor indicators. It seems the vibration of the RF contactors during pattern change would eventually damage the filaments of the incandescent lamps. The lighted switches used the old 24 V telephone key system bulbs. The frequency of bulb failure moved Harry to action. He used the old metal frame that held the incandescent bulb and inserted a red LED for day pattern, a green LED for night, adding a dropping resistor to each LED/frame assembly. See Fig. 3. Harry writes he’s not had a "bulb" failure since.
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Here’s a story to file in the back of your mind in case this ever happens to you.
WBQB(FM) Engineering Manager John Diamantis started noticing a less-than-clean signal on his studio air monitor. After all the usual checks, externally monitoring the signal, he determined the problem was in the monitor system.
Breaking things down into sections, he swapped receivers but the noise remained. He checked the receive antenna; it was properly oriented and there were no corroded connections.
While following the coax through the attic of the studio building, he noticed an old TV preamplifier — unused, but still plugged in.
On a hunch, he called for the operator to listen closely to the monitor. John unplugged the amp. The noise went away. He removed the amp and the problem was solved.
Down on the bench, he found that the little TV booster amp was spewing harmonics. John’s not sure who installed the amp; that was way before his time. It clearly hadn’t been used in years yet had remained plugged in. Maybe an off-air TV feed for the newsroom before cable or direct satellite!
It’s a good thing John’s station isn’t near a cell tower. I bring up the story because in addition to causing John headaches, it reminds me of an FCC action reported recently by the CGC Newsletter.
See tinyurl.com/px6efj. This commission document describes a citation issued to a private citizen whose set-top TV antenna preamp broke into oscillation, causing interference to a nearby cellular tower. It’s great reading.
CGC Editor Robert Gonsett asks: If this citation sticks, why would anyone want to buy a DTV antenna preamp?
Gonsett, whose newsletter also did great work during the recent fires threatening California’s Mt. Wilson, can be reached at email@example.com.
John Bisset has worked as a chief engineer and contract engineer for 39 years. He is international sales manager for Europe and Southern Africa for Nautel and a past recipient of the SBE’s Educator of the Year Award. Reach him at firstname.lastname@example.org. Faxed submissions can be sent to (603) 472-4944.
Submissions for this column are encouraged and qualify for SBE recertification credit.