(click thumbnail)Figs. 1 and 2: ‘Knights of Ni, we are but simple travelers who seek the enchanter who lives beyond these woods …’ But it’s no joke when shrubbery takes over your site. I recently had the pleasure of speaking to a group of broadcast engineers at the South Carolina Broadcasters Association annual conference. Each year, Dielectric Southeast Radio Sales Manager John George works with a panel of peers to provide timely technical presentations.
After my presentation, chock-full of pictures showing how not to engineer sites, Clear Channel Charleston’s Willie Bennett commented how much he enjoyed my “tree” pictures.
Figs. 1 and 2 shows what Willie means. These are great to toss on the GM’s desk, to give him an idea of how bad things could get – if not for you!
In that vein, Cumulus’ Gary Kline forwarded a picture of a bad transmitter road, and suggested we see what other engineers have to share. Fig. 2 shows what over 10 inches of rain will do to a normally passable mountaintop road near Santa Barbara.
Certainly Figure 1 was due to neglect; a tree grew around a guy wire. In Gary’s case, Mother Nature turned the road into a nightmare.
John “JD” Strahler is chief for KRUZ, Santa Barbara. During a severe rain and windstorm, he was dispatched to the transmitter site to restore programming. Once on site, JD found a wind-damaged STL dish and cable. Stahler writes that the road, with all the mud and rockslides, would have been a great place to film a commercial for Jeep.
(click thumbnail)If tree pictures weren’t enough, now we’ll see some of the best and worst transmitter site roads. Send yours. Make sure the picture is of high resolution so we can see the detail in living color. That means 300 dots per inch resolution for publication at 3 to 5 inches wide. Email to me at my new e-mail address, [email protected].
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JD’s adventure serves as a reminder to stock your transmitter site with basics: a jug of water, canned beans, Vienna sausages, tuna or other canned protein. Don’t forget a can opener and a fork.
Seal a few chocolate bars in a fruitcake tin. Also prepare a change of clothes and some blankets packed in those big plastic “freezer” bags, to keep them dry.
Rolls of toilet paper and paper towels, again sealed in the plastic “freezer” bags, are also a must. You can usually find surplus military cots for a reasonable price; add one to your emergency supply. It beats sleeping in a chair. Don’t forget the flashlight, spare batteries and a well-stocked first aid kit.
Are there other “must haves” at your transmitter sites? Let me know so we can include them in a future column. Stay safe.
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Keith Bowman is market engineer for Adventure Radio in Bluefield, W.Va. He came across a fix for his Harris MW5 transmitter the other night. In light of the fact that Harris dropped support for these boxes, he thought this might be something to share with Workbench readers.
For the past few years, Keith has had trouble getting a good, solid-sounding 100-125 percent modulation out of the WHIS MW5 transmitter. The audio wasn’t bad, it just seemed to be deficient in the bottom end. A couple of months ago, Keith installed an Orban 9200 to replace the 9100 that was feeding the transmitter since the late 1980s. This helped the station’s overall coverage dramatically, but Keith still wasn’t happy with the low-end audio, and the poor performance showed up on an audio proof.
Looking at the overall audio path, Keith realized the 1A1A2 audio input circuit (on the PDM control and feedback board) had the original Sprague electrolytic capacitors in it. Remembering back to the old cart machine days, audio could be improved with a “shotgun” approach – replacing all of the caps on the audio board – on an older machine.
(click thumbnail)Fig. 3: Rain, mud and rockslides combine to block a mountain road in California.
Keith decided to try the same approach on this circuit. Before replacing the capacitors, Keith checked them with a Fluke 12 on the capacitance scale. Even though everything checked fine, Keith wasn’t convinced.
He replaced eight of the electrolytics on the board, and presto! The audio sounded better than he had heard it in years. The improvement was also noticed in some of their “spotty” coverage areas.
(click thumbnail)Fig. 4: Ground leads should sweep downward to ground, with no sharp bends.
Keith writes that sometimes vast improvements can be made by looking in the simple places you might not suspect. I agree. In the days of cart machines, the rule of thumb for electrolytics was to replace them every seven years. In older plants, inspect aging audio equipment to see if it still has the original electrolytics, not only in the audio coupling stages, but also in the power supply.
Keith Bowman can be reached at [email protected].
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It won’t be long before many of us are worrying about warm-weather lightning. For readers in some climes, the worry never goes away.
Good grounding of the transmission lines, especially where they enter the building, is imperative. But how do you attach these ground kits?
First, remember that any charge wants to go to ground. The ground lead should not be kinked or loop upward away from ground on its way to the ground block; unfortunately I’ve seen this practice often. It compromises the efficiency of the connection.
Remember in AM plants, the lightning loop of the feeder line from the coupling unit to the tower? That single or double loop of inductance works very hard to keep lightning out of the coupling network.
Fig. 4 shows the ground kits installed properly, all sweeping downward to the ground block. There’s one errant cable on the right that loops around and works its way to the block, but the rest are installed satisfactorily.
Don’t let sloppy work compromise your grounding scheme. As with any project, take the time to do it right.
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