RF Shorts – December 27, 2011

LED 'Sees' Electromagnetic Waves
Makezine.com has an interesting article describing the use of an LED to display electromagnetic waves: Seeing EM Waves With a Single LED. "Radio whiz Greg Charvat just published this video showing off a very cool experiment with the low-cost coffee can radar system he and co-workers developed in the fall of 2010 for MIT's open courseware initiative. In the video, Greg describes and demonstrates a simple circuit that causes a red/green LED on the receiving antenna to glow one color when the amplitude of the received wave is positive, and another when it is negative. Moving the LED back and forth in front of the transmitter, while taking a long-exposure photograph, gives a visual map of the wavefront in space.

Quite impressive.

Woman Jumps From WETA Tower
Washington D.C. television station WRC reported last week BASE Jumper Leaps From WETA Tower - Parachute snagged in trees. "Police say they have never seen anything like this before. A base jumper leaped from a 500-foot tower last night in Arlington, but her parachute got stuck in a tree on the way down." Kristin Stewart and her four accomplices were arrested and charged with criminal trespassing.

Is WiFi Killing our Children?
In RF Report I've attempted to provide balanced coverage of research on the effect of non-ionizing radio frequency energy on living creatures. This week, however, I can't resist posting a link the article WiFI radiation safety a growing concern among parents of school children by Tori Floyd. In the article, she quotes Rodney Palmer, who is with the Safe School Committee, saying, "This is not a question mark. The idea is that we shouldn't kill them to be online."

The article itself isn't unique, but what I found most interesting were the comments after the article. Many of them criticized the scaremongering: "What paranoia and ignorance. These same people probably have never considered that all of us have been literally bathed in signals from cell phones to wireless routers, 24 hours a day for years now, no matter where you are. Even at home, signals from your neighbors' wireless devices are reaching you and your kids. And guess what--they are completely harmless!" Perhaps the title should read: 'Wi-Fi Radiation Safety a Growing Concern Among Feeble Minds.'

Seriously, if you own a mobile phone, tablet, laptop, microwave, or live anywhere in the city, you are bombarded with WiFi round the clock. If there were a health concern, it would have shown itself decades ago when microwaves first started getting used in a big way. There are also comments supporting the claims in the article. Be sure and read the older comments—there's one from an engineer who worked on transmitters.

Also see Radiation from Cell Phones and WiFi Are Making People Sick -- Are You at Risk?. It advises, "Turn off all the fuses at night that supply your bedroom. You can install a 'demand switch' at your bedside to make this very convenient" and "Shield your bed with a special metalized fabric canopy to protect yourself from harmful frequencies that can disrupt cellular communication." The cells it refers to, of course, are the ones in your body, not the wireless sites.

Comments and news items are welcome. Email me at dlung@transmitter.com.

Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.