Mike Seguin, the chief at WXXX(FM) and WVMT(AM) in Vermont, is one of several engineers who found the StarGuide test box useful for the 16-relay cards like ABC (Workbench, Nov. 5).
But Mike adds that the box isn't really necessary for the standard four-relay cards found in StarGuide II and IIIs. There's a "relay test function" in the system menus on these receivers that works the same way as the pushbutton box.
This test function is accessible through:
If you activate a relay to test, make sure to deactivate it, as the command is a toggle. Thanks, Mike for passing on this information. Reach Mike at email@example.com
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Most satellite receivers are located inside dark equipment racks. I've had numerous suggestions from engineers who have used "rope lights" inside a rack to illuminate the equipment, as pictured in Fig. 1.
(click thumbnail)Fig. 1: Rope lights can help illuminate those dark rack interiors. Festive, too.
These lights use minimal power and generate minimal heat, but provide quite a bit of light. The photo shows rope lights used in a dark rack room. The advantage over bulbs or fluorescent tubes is the evenness of light. There's also less chance the bulbs will break as you remove and install equipment.
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Chris Kelley's StarGuide test box also brought an interesting question from Al Kazlaukas at Radio One's cluster in Cleveland.
Al asks where an engineer can find the small parts described in Chris Kelley's test box, with all the Radio Shacks limiting their stock of parts. Al says whenever he enters a Radio Shack, he's offered a deal on a cell phone, but the stock of spare parts keeps shrinking. This is indeed a problem.
For what it's worth, I'd try getting close to the manager of the store. There was a time when most of the stores were franchised that the local manager would do handsprings for your business. Although the managers of company-owned stores might not have the financial incentive of years past, it never hurts to ask.
If the manager knows that he'll sell a stash of XLR or TRS connectors each month, he'll stock them. Explain that you're a radio station, operating 24/7, and you will pay the higher Radio Shack prices to have these small parts at hand. I'm aware of stores that gave the engineer the manager's cell phone, so he could meet late at night or on the weekend to fill an emergency parts order. Now that's service.
Take the manager out to lunch, outline your needs and see what he's willing to do. If there are several stations near the store, get the word out and maybe involve your local SBE chapter.
Al raises a good point. What sources do you use for your small parts supplies? E-mail them to me, and we'll help everyone find those elusive parts.
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Speaking of satellites: Winston Hawkins is the technical director for the Baker Family Stations Group and a Radio World contributor. Winston's group carries CNN news at one of their stations, and Winston got a report that the feed was not working.
The station is some 300 miles from the home office. Trom the symptoms described, Winston thought the receiver might be at fault. After sending the receiver to the repair depot, the receiver was returned with a report that it was OK. With new LNB in hand, Winston made the trip to the station, fairly confident that this would solve the problem.
It wasn't long before Winston found the new LNB didn't solve the problem, either. So he checked the markings that he always makes on the mounting post, to make sure that the wind had not blown the dish off course and that the actuator brackets had not slipped.
Next step was checking for birds and bees in the feedhorn; then the voltage to the LNB, but that was OK. The coax and fittings were like new.
Winston brought along a consumer satellite receiver, which he hooked up to the antenna just to see if the connections and alignment were working. The television connected to the receiver popped up a picture immediately. This was getting to be crazy.
Winston then connected the digital receiver with a DC pass/block splitter, with the consumer receiver powering the LNB. When he did this, all the lights went green on the digital receiver and he had an ebno of 10.0.
What went wrong? It seems the digital receiver's power supply had degraded to the point that the current capacity was not capable of powering the LNB (even though the voltage to the LNB was correct). The system worked fine with the consumer receiver providing the power, until the power supply could be replaced.
(click thumbnail)Fig. 2: How Tom Shedlick handled a space problem.
Once resolved, head-scratchers like this appear easy to diagnose. But it's only a diligent, step-by-step troubleshooting method, as outlined by Winston, that permits you to effectively solve the problem. He can be reached at firstname.lastname@example.org.
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Those pre-fabricated equipment shelters, made so popular by the cellular industry and now being used for broadcast applications, make for clean transmitter buildings. Perhaps the only drawback is the space. You've got to prepare your transmitter and rack layouts carefully to ensure enough room in front and behind equipment. Don't forget the dimensions required to open front and rear transmitter and rack doors.
Tom Shedlick leads a crew of engineers at the Clear Channel cluster in Washington. They're putting the finishing touches on a three-station multiplexed project. As you can imagine, when you add those combiners to the transmitter building, space is tight.
Fig. 2 shows what Tom did with his dehydrator. Unistrut and Kindorf products make support of even dehydrators an easy task. Getting the dehydrator up in the air gives you more floor and wall space, while the unit is still accessible using a step stool.
(click thumbnail)Fig. 3: Anchor the strut with lag bolts to secure the installation.
If you have any questions about the weight this strut material can handle, look at Fig. 3. Some transfer switches can weigh 70 pounds or more. Anchoring the strut with lag bolts into the wall secures the installation. By pointing the channel down, so the mounting bolts slide in place, there's enough wiggle room or tolerance between the switch mounting tabs.
Reach Tom via e-mail to email@example.com.
Submissions for this column are encouraged, and qualify for SBE recertification credit.