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A Better Way to Go Fishing

College students scrounge for furniture. Usually they end up with hand-me-downs from home or the Salvation Army...Joe Brannan is program director and engineer of WEGL at Auburn University in Alabama, and an electrical engineering student at the university. When it was time to retire the station's Scientific-Atlanta SEDAT receivers, Joe sprung into action.

College students scrounge for furniture. Usually they end up with hand-me-downs from home or the Salvation Army.

Joe Brannan is program director and engineer of WEGL at Auburn University in Alabama, and an electrical engineering student at the university. When it was time to retire the station’s Scientific-Atlanta SEDAT receivers, Joe sprung into action.

(click thumbnail)Fig. 1 WEGL’s old Sedat receivers make a nice TV stand.
The receiver was first used to hold up a speaker in his surround-sound system. It makes for a great $16,000 conversation piece – especially since it still lights up.

But furniture evolves in the college dorm. Its latest use, as seen in Fig. 1, is as a TV stand.

Chris Waldrup, former engineer for Curtis Media in Raleigh, N.C., now with Integrian at the Research Triangle Park, uses these old satellite receivers in a different way.

An avid ham and bread-boarder of circuits, Chris cannibalizes them for the ceramic trimmer caps, Mini-Circuits mixers, silver mica capacitors, socketed chips and MBD101 hot carrier diodes, which are now obsolete in leaded packages. The SEDAT boxes also contain high-quality Jensen audio transformers, useful for building projects.

As for removing the components, Chris suggests using an ordinary heat gun (Weller, Master Mite, Easypower). These do an excellent job of desoldering components, including Ics when coupled with some solder wick. Guns that operate in the 750 to 800 degree range are best; hotter guns tend to burn the board.

. . .

We all have to fish RG-6 or smaller coax and low-voltage plenum wiring through tight spaces. Due to a lack of rigidity, threading the cable through floor joists, attic crawl spaces, or above dropped ceilings makes the job nearly impossible. Even a fish tape will bend and curl, leaving the “fish-ee” ready to go fishing.

(click thumbnail)Fig. 2 Bob Hughes calls this his Ronco/Popeil Cable Pusher.
I’ve pestered my friend Bob Hughes, who has worked on the air in Washington, programmed stations and engineered them, to draw on his experience and contribute something to Workbench. Bob is now the manager of the Visual Recording Facility at the Pentagon. Drawing from his own frustration in “fishing” cables, he came up with an inexpensive solution.

Bob calls it his Ronco/Popeil Cable Pusher, perhaps lobbying for wider distribution with that famous widgets company. You can see it in Fig. 2, thanks to his daughter Ashley’s skill with a camera.

Construction is simple. Take a length of 1/2-inch PVC pipe (length to be determined by individual needs, and the length of your arm), cut it to size and thread the cable through it to its destination. By using the PVC to “push” the cable along, you’ll be afforded the necessary rigidity to accomplish the task, with a minimum of frustration and aggravation.

Once the cable gets to its destination, remove the PVC pipe and make your connection.

. . .

One morning, not long ago, Jon Hosford, director of engineering for Montpelier Broadcasting, got that dreaded call from a DJ. The building smelled like something was burning, and the ISDN line, used as an STL, was down.

Jon uses a Telos Zephyr Classic to get audio to transmitter, 30 miles from the studio. As always seems to be the case, there’s no backup.

Jon quickly diagnosed the problem to be related to the power supply, but the Zephyr supply provides +5, +12 and -12 VDC. At 5 in the morning, and with no -12 VDC supply handy, it occurred to Jon that a normal computer power supply would have those outputs.

Within 15 minutes, the Zephyr was back on the air. It didn’t look pretty, but worked until Telos overnighted a replacement.

Why it never occurred to Jon to use an old computer supply for a DC supply, he’s not sure. But a typical 200-watt computer supply can provide 20A @5VDC, and 8A @12VDC. Even though the -5 and -12 volt supplies are only 0.5A, in a bind that could be just enough power to get you by. The larger 350W supplies can handle even more of a load.

Everyone has at least one junked computer laying around. And even if there isn’t one, sacrificing the computer the jocks use to surf the Net will work to get the station back on the air.

. . .

Speaking of power supplies, Jim Arcaro of Cleveland writes about a problem you might want to check into, if you have programmable uninterruptible power supplies.

Jim got called to a site where the computer network was down. There was a direct lightning hit to the power line, and the fuses in both the UPSs and the DSUs blew.

Jim thought it strange that the customer DSUs should blow, as they were after the UPS, and all equipment was grounded by a dedicated #6 ground wire.

Jim plugged the equipment directly into the wall and got some of it working. He then replaced the fuse in the UPS, and let its batteries start to charge.

While replacing the fuses in the DSUs, however, Jim noticed they were only slightly brown, not black as one would expect with a direct hit. He called the manufacturer of the DSU and was informed by the technician that the maximum rated input voltage was 130V.

Checking the UPS, which was programmable, Jim found that it was set for its maximum of 138V. Jim reset all the UPSs to 128VAC. By the way, he also checked the brownout voltage. It was OK at 105V. The tech rep said the DSU would work fine down to 90V.

Thanks to the UPS, the routers and hubs were unfazed by this, but the dial-up modem took a hit through the phone line, even though the telco was protected with gas tubes. A monitor, printer and print server were saved by a hig-quality surge strip, which took the hit and was sacrificed.

The lesson learned? Jim is plugging the UPS into a wall-mount surge protector. He admits that it’s redundant, but if it blows, he can just plug the UPS into the wall outlet and keep running while replacing a $50 item instead of the $900 item, at his leisure.