Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Gian Luca Cavalliini]

Hi gurus,

I know, generally speaking, RF waves can travel through non conductive materials, while is blocked by metal, water ecc.

1) Is there a reference table reporting coefficient of permeability of different materials?

2) I can't find reference of reflective vs absorption properties. I mean: is wave energy just divided in refracted and reflected? Or, as with sound wave, some materials have absorption (energy conversion) properties?

Thanks!

[Henry Cohen]

Hi gurus,

I know, generally speaking, RF waves can travel through non conductive materials, while is blocked by metal, water ecc.

1) Is there a reference table reporting coefficient of permeability of different materials?

2) I can't find reference of reflective vs absorption properties. I mean: is wave energy just divided in refracted and reflected? Or, as with sound wave, some materials have absorption (energy conversion) properties?

I don't know of a comprehensive catalog or table of attenuation vs frequency vs material type, but a search for "rf attenuation various materials" returned a number of results for testing various sets of materials, mostly building products, as well as purpose manufactured shielding materials.

If you're looking for test results of textiles, I can say categorically chainmail jackets are not very RF permeable below about 180GHz 

[Russell Ault]

Hi gurus,

I know, generally speaking, RF waves can travel through non conductive materials, while is blocked by metal, water ecc.

1) Is there a reference table reporting coefficient of permeability of different materials?

2) I can't find reference of reflective vs absorption properties. I mean: is wave energy just divided in refracted and reflected? Or, as with sound wave, some materials have absorption (energy conversion) properties?

Thanks!

This answer on the Electrical Engineer Stack Exchange might start you down the right path.

Basically, it's complicated. Even saying that RF waves are "blocked" by metal and water isn't quite accurate (although it's a pragmatic assumption). The electromagnetic absorption characteristics of water are state-dependent. Many metals are quite conductive (hence why we use them in RF cabling), but the boundary between air and metal can cause significant reflections (which will look like "blocking") depending on the shape and size of the object in question: if the object is small enough or has large enough holes (relative to wavelength) then the waves will largely refract around (which is why UHF radios work better indoors than, say, CB), and if the object is just the right size (again, relative to wavelength) then there will be little-to-no reflection and transmittance will occur instead (i.e. an antenna). All of which is to say that the "blocking" effect of a particular material has as much to do with its surroundings as with the material itself.

(For what it's worth, the term "permeability" in this context usually refers to magnetic permeability, which doesn't necessarily help with electromagnetic characteristics, or rather, not at UHF frequencies anyway.)

-Russ

[ProSoundWeb Community]