Dale Heidner of KGVW and KCMM in Belgrade, Mont., read our Workbench advice on checking capacitors. Dale adds a simple and alternative method he wanted to share.
Take your Fluke 77 DMM meter and set it to the DC range. Measure your DC supply voltage. For example, let's say the DC supply is supposed to be +15 VDC. You measure +15VDC on your Fluke. Now set the Fluke 77 to the AC position and read your AC voltage.
Usually, Dale likes to see a ripple voltage of about 0.005 VAC on his Fluke 77. When Dale checked his Heathkit power supply in the 300VDC mode, he measured a ripple voltage of 0.007 VAC.
Try it! The technique will save you from lugging your 'scope up to a mountain site to check the power supply in your STL receiver.
Dale Heidner, W7NAV, can be reached at email@example.com.
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I received two notes from engineers regarding the wasps and the rubber ice-flaps used to "weatherproof" outdoor padlocks.
(click thumbnail)Fig. 1: Flaps cover and protect locks ... but provide a haven for stinging insects.
The first was a warning from Randy Kerbawy, engineering Manager for Southern Communications in Beckley, W.Va. Randy writes that the rubber flaps covering padlocks is also a great place for wasps and other critters to hide.
Randy wears the battle scars from at least one wasp attack, surprising the varmint as he reached under the flap to open a lock. As colder weather approaches, the problem is particularly bad.
We mentioned one solution, spraying some wasp killer under the flap that should discourage the visitors. Although the rubber ice shields are helpful, beware!. Randy Kerbawy can be reached at firstname.lastname@example.org.
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Who would ever believe that there would be angry wasps in as pretty a city as San Francisco? Lou Schneider is on the engineering staff for Bonneville's San Francisco Radio Group, KOIT(AM-FM), KDFC(FM) and KZBR(FM). He's found that Dow Bathroom Cleaner With Scrubbing Bubbles is the most effective way to deal with angry wasps.
The version in the aerosol can works best. Just spray it in their vicinity, and as soon as the Scrubbing Bubbles touch their wings it foams up and they drop like a stone. If you want to follow up with regular wasp spray, the Bubbles will keep them disabled while the insecticide finishes them off. Or you can just step on them. Squish.
You might wonder how Lou made this discovery. About 20 years ago, Lou disturbed a large nest inside a transmitter room, an angry swarm formed between Lou and the exit. In his haste, Lou grabbed the wrong spray can, and was pleasantly surprised with the result. The Scrubbing Bubbles worked like a champ and he escaped without getting stung. Since then, Lou keeps a couple of cans at his transmitter sites.
Lou Schneider can be reached at email@example.com.
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As the holiday's approach, the folks at SCOTTeVest Inc. have introduced several products to include in your holiday gift guide. The company offers what it calls Technology-Enabled Clothing, which permits wires from electronic devices to be routed through a patent-pending Personal Area Network.
Although they're a favorite of the "technical geek" crowd, travelers also like these thanks to features such as pockets galore, up to 44.
Now, in addition to being able to carry and connect devices, you can charge them with the solar-powered SeV. So get charging.
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Marcus Damberger is with KBIM(TV) in Roswell, N.M. He was checking out Workbench columns archived at RW Online and appreciated the air conditioning suggestions we've offered. Reading those inspired Marcus to ask about a solution to a problem readers might have come across.
Marcus writes that New Mexico is "translator land," second only to Utah. While maintaining sites, he has come across frozen air conditioner condensation coils - specifically in window units that tend to be used where access is hard and the HVAC repairman can't easily get to the top of the mountain. Often a spare window unit will be available on site to replace one that might fail.
Marcus' question is whether any readers have come across a probe of some kind that could detect the freezing of the coils and shut off the A/C until the ice melts. Marcus adds, "Something like the Waterbug, but only for freezing?" He refers to the Waterbug brand water protection device.
(click thumbnail)Fig. 3: Ventilation holes are drilled in removable panels ...
I'm not aware of anything; but perhaps mounting a Burk/Gentner temperature probe up against the coil, tie it to the remote control, alarm it, then use something like a Henry Super Relay to interface to the remote control for turning the A/C off and on.
E-mail suggestions to me at firstname.lastname@example.org. Published submissions qualify for SBE recertification credit.
Marcus Damberger can be reached at KBIM(TV), email@example.com.
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One of an engineer's biggest challenges is using older console furniture in a state-of-the-art studio.
Rich Hill, engineering manager for Citadel's Harrisburg, Pa., cluster, was faced with this dilemma while planning a facility. Although the existing furniture would suffice until the move, heat generated by rack-mounted computers and other equipment mounted in the vertical rack space could be a problem.
(click thumbnail)Fig. 4: ... and inexpensive grilles are added to provide ventilation.
You've probably seen stations where the only choice for ventilation was to leave the finishing panels off the backs of the cabinetry. Rich had a better idea. He drilled three large holes in the cabinet's removable panels and covered the holes with ventilation panels that cost under $1 each.
Since Rich showed me his handiwork, he's planning to add small muffin fans to circulate air through the rack equipment, further improving ventilation.
Submissions for this column are encouraged, and qualify for SBE recertification credit.