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Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ.

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RE: You might want to read

Posted by Steve Eddy on April 9, 2011 at 07:35:37:

Could you please explain?

Sure.

It all depends on the type of source and your distance from the source as it relates to the wave impedance which is the ratio of the E- and H-fields.

In the far field, the wave ratio will essentially be that of free space, or 377 ohms.

The nearfield extends about one sixth of a wavelength from the source and depending on the source, the ratios of the E- and H-fields won't be the same as in the far field.

In the nearfield of a loop antenna, the wave impedance is lower than 377 ohms which means it's predominantly H-field. So magnetic shielding will be more effective than electrostatic shielding.

In the nearfield of a whip antenna, the wave impedance is higher than 377 ohms which means it's predominantly E-field. So electrostatic shielding will be more effective than magnetic shielding.

se