RF Protective Clothing Evaluations

One viable means of RF exposure mitigation is the use of RF protective clothing. This is clothing, in the form of overalls, that is constructed from fabric containing microscopic stainless steel fibers. The metallic content of the fabric can afford a substantial reduction in body absorption of RF energy for personnel having to work in the vicinity of powerful transmitting antennas. Richard Tell Associates has participated extensively in the issue of how to perform tests of the effectiveness of RF protective clothing. These studies have included projects with both Motorola (NSP America, Inc.) and Euclid Garment Manufacturing Company.





Laboratory investigations of the shielding effectiveness of different RF protective suits were performed by applying state-of-the-art measurement techniques. Using a life-sized phantom model, filled with an RF absorbing liquid to simulate the electrical characteristics of tissue, a small, robotically controlled electric field probe was used to scan the interior of the phantom while it was exposed to known RF field levels. By performing measurements with and without the suit under test on the phantom, direct measurements of the specific absorption rate (SAR) were obtained.

Using SAR as the criterion of exposure was deemed to be the most meaningful measure of suit performance when compared to simple measurements of RF field strengths in air. An example measurement result illustrates the effect of one suit on near-field exposure reduction evaluated at 450 MHz. Other studies of the ability of protective clothing to reduce induced body currents and contact currents have been performed. For examples, see the evaluations of an RF protective suit at a high power AM radio broadcast transmitter site and a high power VHF-UHF broadcast transmitter site.

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