Every once in a while we get a great engineering horror story to share. This one is from Citadel's Bill Frahm, who handles engineering for Citadel's Boise properties. We'll call this "Listening to a Water Pipe."
So there's this lawn guy who has been hired to spray for weeds around a 50 kW tower. Against instructions, he doesn't tell anyone he's arrived early and goes out to the tower, ahead of the engineer (and the power reduction).
Wanting to do a thorough spray job, he scales the six-foot fence, ignoring the "No Trespassing" and RFR signs. He hears talking and music coming from "that copper water pipe" — and proceeds to put his ear up to it!
Fortunately, he wasn't killed, just a bad burn on the ear.
Fig. 1: Finally, a USB surge suppressor. It seems no matter how hard we secure our sites, someone will be intent on defeating the security.
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As I noted briefly last issue, the "bees" we mentioned in Tom Ray's recent item actually were paper wasps that had made their nest on the door of the tuning unit. (And the hive seen under the stepladder in our subsequent column is typical of what bald-faced hornets build.)
Yes, "bees" refer to honey, bumble, killer and carpenter varieties.
As a kid, I was allergic to stings, so anything that flew and stung was a bee to me and to "bee" avoided. Guess those old definitions die hard!
Thanks for making the distinction and setting things right. I hope your encounters with these insects will be minimal in the months ahead ... "Raid to the rescue."
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Here's a neat product for experimenters. L-com, a manufacturer of wired and wireless connectivity products, has released a panel-mount USB surge protector. The product, AL-ECF504-AB, pictured in Fig. 1, is a commercial-quality device designed to protect a computer's sensitive USB ports from surges and spikes from attached devices.
At issue with this kind of protection is to ensure that USB speeds are not affected by the surge-limiting components. The device uses ultra-low capacitance diodes to protect the data lines. In addition, a protection device clamps the power lines to safe levels. This USB surge protector is ideal for protecting a PC from USB-connected devices including USB hubs, WiFi USB client adapters and USB-enabled surveillance cameras. The surge protector costs less than $16.
More information can be obtained from www.L-com.com.
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Fig. 2: LEDtronics' new screw-in white LED right angle 'bulb.'
Fig. 3: Use a 680 ohm resistor in the Marti STL-R10 Receiver to convert to LED meter lighting. LEDtronics offers the S6 Right-Angle Candelabra LED Bulbs. These LED bulbs fit almost any S6 screw base sockets, as seen in Fig. 2, and include a right-angle mounting fixture-to-lens setup.
These high-quality LED bulbs produce little heat, consuming 0.935 watts of power compared to the usual 4 or 7 watts for an incandescent bulb.
For a data sheet, visit www.ledtronics.com/ds/slr463/default.asp.
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Speaking of light, Buc Fitch's replacement LED meter lamps for the Marti STL-10 Transmitter brought a lot of positive comments. It looks like Buc's not the only one tired of burned-out meter bulbs.
However, the R10 STL Receiver needs a different current limiting resistor than what was used in the STL-10 Transmitter. Fig. 3 shows a single 680 ohm 1/2 watt current limiting resistor, and once again, a 20 ma white LED.
Buc cautions, though, that some of these receivers (like the STL-10 transmitter we covered in the Aug. 1 Workbench) have a diode ahead of the lamp supply. So be sure to check the polarity on the supply (or clip lead test the LED) before soldering it in place, as the voltage can be DC.
Fig. 4: Adding a resistor, foreground, to the meter switch ends pegged meter indications.
Fig. 5: Normal meter indication, after Buc's resistor mod. Buc offers one more useful mod to this workhorse STL receiver. Fig. 4 shows a 10 k resistor added in the "mixer" line to the meter switch. Many of these Marti R-10s had this reading literally off-scale (well pinned) even when properly adjusted. If you are bothered by "off-scale" readings, just add this resistor in series with the green/white wire before the switch, and the peak will appear about "0" on the meter VU scale, as shown in Fig. 5.
He adds a reminder to remove all the dust and cobwebs before returning the device to service.
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 SBE's Educator of the Year Award. Reach him 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.