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3910.3A <br /> 10/ 19/83 <br /> b. Engineering Controls <br /> (1) That portion of the radar transmitting system lying between <br /> the RF generator and the antenna feed horn is a closed system and shall <br /> remain so while the system is energized. Waveguides, waveguide switches, <br /> and enclosures around RF generators provide sufficient shielding from RF <br /> radiation exposure provided that the integrity of all joints in the <br /> system is maintained. <br /> (2) In the event that further shielding is required for special <br /> purposes, the attenuation factors for various materials shown in Figure <br /> 3-4 may be used as guidelines. <br /> FIGURE 3-4. ATTENUATION OF RF RADIATION <br /> PROVIDED BY VARIOUS TYPES OF SHIELDING <br /> From Palmisano, W.A. and D. H. Sliney, "Instrumentation and Methods Used <br /> in Microwave Hazard Analysis, "U.S. Army Environmental Hygiene Agency, <br /> Edgewood, MD. Presented at American Industrial Hygiene Conference, 1967. <br /> Frequency (GHz) <br /> 1-3 3-5 5-7 7-10 <br /> Attenuation (dB) <br /> 60 x 60 mesh screening 20 25 22 20 <br /> 32 x 32 mesh screening 18 22 22 18 <br /> 16 x 16 window screen 18 20 20 22 <br /> 1/4" mesh (hardware cloth) 18 15 12 10 <br /> Window glass 2 2 3 3.5 <br /> 3/4" pine sheathing 2 2 2 3.5 <br /> 8" concrete block 20 22 26 30 <br /> c. Procedural Controls. <br /> (1) Personnel shall not work on the antenna, waveguide, or <br /> feedhorn structures of a transmitting radar. <br /> Chap 3 <br /> Page 30 Par 36 <br />