This is another question related to magnetic fields. I'm trying to determine the thickness of copper foil that would be required to shield common electronic items from H fields of about 133 A/m over a range of frequencies from 1-1,000 MHz. I'm shooting for 50 dB of attenuation, and I'm trying to include cost and other practicalities among the considerations.
Based on the fact that 35 microns of copper foil attenuates an H field by 8.6 dB at 4 MHz, I calculated that a 407 micron thickness would be required to provide 50 dB of attenuation at 1 MHz. This is twice as much shielding as what's required at 4 MHz, four times as much as what's needed at 16 MHz, and much more than what's required at 1 GHz. In short, it's overkill for most frequencies.
So, my question is: what kinds of electronic items are most likely to couple damaging currents in a very strong H field at 1-36* MHz? Any item that contains a coil antenna that's sensitive on any of these frequencies would make the list. One item that comes to mind immediately is an AM radio (which might lower the lowest frequency of interest to around 500 kHz or lower, although this would require a thickness of copper that I think would be impractical). I can't think of any other kinds of items that would contain loops or coils long enough to couple an H field at these relatively low frequencies. Any suggestions? (Again, please consider a range of 1-36* MHz.)
* I chose 36 MHz as an upper limit, because 68 microns of copper would be required at that frequency, and I think this might be a reasonable thickness. It might not be the best thickness based on how many types of items would be susceptible to damage at lower frequencies, though, so I'm open to suggestions.