DEVELOPMENT OF BROAD-BAND ELECTROMAGNETIC ABSORBERS FOR ELECTRO-EXPLOSIVE DEVICES.
Monthly progress rept., 1-31 May 63,
FRANKLIN INST PHILADELPHIA PA LABS FOR RESEARCH AND DEVELOPMENT
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To attain high attenuation in the des ex perimental ferrite attenuators, it was found that those ferrites which have a low volume resistivity and high initial permeability gen erally are the best ones to use however, the resulting low dc resistance and low voltage breakdown are not desirable. To eliminate these disadvantages, ferrites were insulated with ceramic sleeves having a high dielectric con stant the attenuation of insulated samples did not increase proportionally with length. Study showed that thin samples, separately insulated, combined in a composite length actually did give the predicted amount of attenuation. The attenuation of various lengths of ferrites at frequencies of 150, 250, and 500 Mc was meas ured. A graph is included which shows the re lationship of attenuation versus sample length of uninsulated and insulated samples. Prelim inary analysis of the graph seems to bear out previous tests in that thin insulated samples give the highest attenuation per unit length. Total attenuation of an insulated sample ap proaches a maximum value where further increase in its length has no effect on attenuation. The reason for this is not fully understood, but a reference is given which might shed more light upon the problem. Author