Testing newspaper using the spec MIL-DTL-83528 resulted in shielding results of 60, 75 and 93 dB. The purpose of using newspaper for the test was to illustrate that the test is highly flawed and should be replaced. A detailed analysis illustrates that the newspaper test could have revealed an inflated level of about 70 dB instead of the 33 dB (93 – 60 = 33 dB) in the test results.
The test is a modified MIL-STD-285 test. The modifications are:
- The transmitting antenna is aimed at the center of a large 26×26 inch aluminum plate instead of at the gasket under test.
- The receiving antenna is situated directly behind the large aluminum plate instead of at the maximum field strength from the wave leaving the gasketed seam.
The second modification has proven to provide an inflated level of shielding of more than 40 dB (Chomerics and other test facilities have recorded more than 100 dB of shielding for a sheet of newspaper at 2 GHz). A detailed analysis associated with aiming the transmitting antenna at the seam holding the newspaper revealed a shielding of the newspaper at closer to 30 dB (29.4 dB). The actual inflated shielding is there for 100 – 30 = 70 dB. We thought that the results of our test illustrated what we wanted to show (the test is highly flawed). Had we been interested in performing an actual MIL-STD-285 test, the inflated level would have been closer to 70 dB.
The SE test contained in MIL-DTL-83528 should be changed to provide the design engineering community with accurate information they can use in the selection of a gasket. That can only occur with the consent of the custodian of the document.
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