The Challenge
I wanted to find an effective yet inexpensive shielding material. I had tested several materials and found aluminum screening to be quite effective at shielding in the 2.4 and 5 GHz ranges, which covers most WiFi routers and wireless devices.
Prototype WiFi Cage
I decided to test the effectiveness of aluminum screening as a shielding medium. So, I hobbled together a prototype router cover/shield. It is not pretty. But, it works and it proved, to my satisfaction that aluminum screening, when properly positioned, provides an excellent shielding for RF frequencies in the 2.4 GHz and 5 GHz ranges, which means most WiFi Routers.
Prototype Fabrication
I cut the aluminum screen to size and fastened it together with a hot glue gun. Do not laugh. I know it is ugly. That was not the point. The point was to determine the cost effectiveness of aluminum screening as shielding material. This router cover cost less than a dollar to make. Check the reduction percentages below.
Shielding Results
I was testing an Xfinity modem/router located in our living room. The goal was to be able to use our iPads and still be within the Building Biology Precautionary Guidelines. The router was located about 20 feet from where we sit.
Using my Gigahertz HFE59B RF meter, I took multiple readings with the router cage on and then removed. These readings are the averaged “Peak hold” readings. I recorded the highest reading across multiple tests and then averaged them. There was a consistent average reading, with occasional “spikes.”
No Shielding
Average: 3.40 mW/m2, Spikes: 5.72 mW/2
With Shielding
Average: 0.28 mW/m2, Spikes: 0.64 mW/m2
Percent Reduction
Reduction Formula: shielded – unshielded / shielded * 100 = percentage reduction
Average: 3.40 – 0.28 / 3.40 * 100 = 91% reduction
Spikes: 5.72 – 0.64 / 5.72 * 100 = 88% reduction
WiFi Still Functional
Even with a 90% reduction in RF field strength, our iPads still functioned. We were able to watch YouTube videos with no discernible problem. On testing the connection speed, it was reduced, as expected. However, the reduced speed was fine for our use and the shielding put us in a safe range, according to the Building Biology Precautionary Guidelines.
The prototype router cage, shielded 90% of the RF (Radio Frequency) transmission from the WiFi router. It put our RF exposure within the Building Biology Guidelines, of < 1 mW/m2 (less than 1 millWatt per meter squared). And we are receiving, no more than 0.64 mW/m2 even on the spikes. Safe, functional & inexpensive.
Aluminum Screening as Cheap & Effective Shielding
This was highly successful in showing an inexpensive shielding technique. Now that I have proven the aluminum screening is an effective shielding, I will build a more aesthetic cage with it. What is more important is that this demonstrates the effectiveness of aluminum screening in situations where cost might be a factor.
Aluminum screening bought in small bulk 100 foot rolls, costs about 30 cents per square foot. Comparable shielding fabrics are closer to $3.50 per square foot. Some of them are sheer and quite attractive, but at ten times the cost. Depending on the requirement and budget, aluminum screening may be an alternative shielding in specific cases.
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