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Is there any material that will absorb very low frequency radio light? I know that stealth aircraft use radar absorbant materials in their design that absorb radio light best at certain frequencies, but I cannot find any information on materials that are explicitly stated to absorb very low frequency radio light.

I am not looking for any aspect of geometry such as faraday cages - only materials.

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  • $\begingroup$ I've tried an RF absorptive material at 63MHz, and it still wasn't enough frequency to do anything. I can't imagine anything being absorbed in the kHz region. $\endgroup$ – PJazz Jul 3 '19 at 3:03
  • $\begingroup$ ... maybe try a coil tuned to that frequency.... Might absorb a few dB's of the wave, while making the remaining wave propagation very skewed. $\endgroup$ – PJazz Jul 3 '19 at 3:05
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a chunk of material will absorb electromagnetic radiation if 1) its characteristic impedance is close to that of a vacuum (to minimize reflections) and 2) if its impedance contains the right amount of ohmic resistance, so as to dissipate the radiation into heat and not re-radiate it.

that said, to interact significantly with EM radiation of any wavelength requires (ideally) that the size of the interacting object be a significant fraction of the wavelength of that radiation. This means that to absorb centimeter-range radar requires something like a centimeter of thickness to the absorbing layer.

Different rules apply if you are interested in just reflecting away the incident EM waves. In this case, a faraday cage will work.

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