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 MIL-HDBK-419A
Screen shields should use a single or double layer of copper or brass mesh of No. 16 or 22 gauge wire with
openings no greater than 1/16 inch. A mesh less than 18 by 18 (wires to the inch) should not be used. The mesh
wire diameter should be a minimum of 0.025 inch (No. 22 AWG). If more than a nominal 50 dB of attenuation is
required, the screening should have holes no larger than those in a 22 by 22 mesh made of 15 mil of copper
wires. The attenuation of an electromagnetic wave by a mesh is considerably less than that afforded by a solid
metal screen. The principal shielding action of a mesh is due to reflection. Tests have shown that mesh with
50 percent open area and 60 or more strands per wave length introduces a reflection loss very nearly equal to
that of a solid sheet of the same material.
Figure 8-18. Measured and Calculated Shielding Effectiveness of
Copper Screens to Low Impedance Fields (8-8)
8-37
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