Smart Meters Causing RFI

SmartGridElectronics.Net is reporting that some smart meters are causing RFI. In an article published today, they say:

The smart meters that Central Maine Power Company (CMP) is installing throughout its territory pursuant to Commission approval are causing radio frequency interference with some customers’ electrical appliances, personal computers, and communications devices. To date, over 200 customers have contacted CMP about problems with a variety of appliances and devices including phones (cell, cordless, and landline), answering machines, Internet routers and wifi, personal computers, TVs, garage doors, fire alarms, clocks and even electric pet fences. The most common problem is interference with wireless internet routers, because they use similar radio frequencies. The problems can often be resolved by simply changing a setting on the device. Other concerns include malfunctioning phones, Internet routers crashing or freezing, damage to computer hard drives, static and clicking sounds on communication and computer gear, inability to stream Netflix, failure of TV remote, and other appliance malfunctions.

Fortunately, they’re not using BPL for this project. They’re using some kind of wireless networking in the 2.5 GHz band. Even so, it makes you wonder if anyone ever did any EMI/RFI testing on these devices.

ZDNet Australia has also published an article on this situation.

Are Cell Phones Bad for the Brain?

On the IEEE tech talk blog, editor Tekla Perry reports on a new study that shows that holding a cell phone to the ear increases the metabolic activity of nearby brain tissue. She writes:

What this means for long term health is unclear, but it certainly supports the calls of those who want more research, and those who are practicing prudent avoidance by trying to select cell phones with the lowest radiation and limiting their talk time.

I’m not sure how relevant this study is to HT use, but my guess is that the transmit duty cycle is a lot lower for an HT user than a cell phone user. Interesting stuff, nonetheless.

Antenna Problem

Lou, W0IT, sent a link to this video to his brother Ralph, AA8RK, who passed it along to me. It’s a 10 Mbyte download, but worth the wait:


It shows a microwave antenna chock full of acorns, but this description doesn’t do the video justice. Click on the photo to download it. Really.

What do we learn from this? Acorns make a good microwave shield.

A Hip Look At Microwaves

I’m not much of a microwaves freak, but if I was I would visit Microwaves101.Com. According to the website, Microwaves101 is the “numero-uno source for microwave information since the previous unenlightened century.”

Here’s what they say that you’ll find there:

  • The basic concepts of microwave design theory in hypertext encyclopedic format!
  • Practical rules of thumb and other sage advice from Microwave O.F.s!
  • Useful microwave formulae presented in enter-and-click calculator formats!
  • The best microwave acronym and abbreviation dictionary anywhere!
  • Who was that masked man? The Unknown Editor needs to be placed under observation!
  • A virtual lobby filled with the best microwave vendors who want to be your friends!
  • A message board for technical and not-so-technical interchange!
  • An easy way to win a cool Microwaves101 pocketknife!
  • Tons more great stuff, bookmark the site, then look around!

What you won’t find there:

  • Pipe-smoking academic eggheads pondering esoteric, nerdly theoretical derivations to put you to sleep! But we do offer links to them….
  • Pictures of potatoes with arrows poking into them supporting any form of calculus!
  • Yuppie daytrader information spotlighting the latest microwave millionaire!
  • Greed-induced salary surveys to inflate your ego while you avoid real work!
  • Anybody complaining about anything that is “not fair” or politically incorrect!

NIST Finds “Metafilms” Can Shrink Radio, Radar Devices

This is from the March 18, 2008 issue of NIST Tech Beat. It seems to me this technology could also be used at UHF, VHF, and perhaps even HF frequencies……Dan

Recent research at the National Institute of Standards and Technology (NIST) has demonstrated that thin films made of “metamaterials”—manmade composites engineered to offer strange combinations of electromagnetic properties—can reduce the size of resonating circuits that generate microwaves. The work is a step forward in the worldwide quest to further shrink electronic devices such as cell phones, radios, and radar equipment.

Metamaterials may be best known as a possible means of “cloaking” to produce an illusion of invisibility, somewhat like the low-reflectivity coatings that help stealth fighter jets evade radar. As described in a new paper,* NIST researchers and collaborators performed calculations and simulations of two-dimensional surface versions, dubbed “metafilms,” composed of metallic patches or dielectric pucks. Vibrating particles in these metafilms cause incoming electromagnetic energy to behave in unique ways.

The researcher team deduced the effects of placing a metafilm across the inside center of a common type of resonator, a cavity in which microwaves continuously ricochet back and forth. Resonant cavities are used to tune microwave systems to radiate or detect specific frequencies. To resonate, the cavity’s main dimension must be at least half the wavelength of the desired frequency, so for a mobile phone operating at a frequency of 1 gigahertz, the resonator would be about 15 centimeters long. Other research groups have shown that filling part of the cavity with bulk metamaterials allows resonators to be shrunk beyond the usual size limit. The NIST team showed the same effect can be achieved with a single metafilm, which consumes less space, thus allowing for the possibility of smaller resonators, as well as less energy loss. More sophisticated metafilm designs would enhance the effect further so that, in principle, resonators could be made as small as desired, according to the paper.

The metafilm creates an illusion that the resonator is longer than its small physical size by shifting the phase of the electromagnetic energy as it passes through the metafilm, lead author Chris Holloway explains, as if space were expanded in the middle of the cavity. This occurs because the metafilm’s scattering structures, like atoms or molecules in conventional dielectric or magnetic materials, trap electric and magnetic energy locally. The microwaves respond to this uneven energy landscape by adjusting their phases to achieve stable resonance conditions inside the cavity.

On the downside, the researchers also found that, due to losses in the metafilm, smaller resonators have a lower quality factor, or ability to store energy. Accordingly, trade-offs need to be made in device design with respect to operating frequency, resonator size and quality factor, according to the paper. The authors include two from the University of Pennsylvania and a guest researcher from the University of Colorado.

* C.L. Holloway, D.C. Love, E.F. Kuester, A. Salandrino and N. Engheta. Sub-wavelength resonators: on the use of metafilms to overcome the λ/2 size limit. IET Microwaves, Antennas & Propagation, Volume 2, Issue 2, March, 2008, p. 120-129.

Microwave Hacking, Anyone?

I’m not much of a microwave guy, but the article “Mattel makes a real radar gun, on the cheap” on RF Design Line looked intriguing to me. Designed to measure the speeds of Hot Wheels model cars zipping around a track, it emits and detects a pulsed 10.5 GHz microwave signal. It seems to me that you could buy two of them (they cost $30 each) and with a little hacking get them to send and receive CW at the very least.

The article has a lot more technical detail. Perhaps someone with more microwave experience could take a look and tell us what they think.