Posted by S Andreason on
URL: https://www.es-forum.com/EMF-Blocking-tp3349069p3379710.html

I might be wrong about that. The magnetic component may indeed travel
for miles, but in logrthmic fashion it drops off rapidly with distance.

To quote from a smarter book: " Power flux density (also called
electromagnetic field, measured in W/m2) really consists of two separate
fields: The electric field (measured in V/m) and the magnetic field
(measured in A/m). However, as these do not exist separately anymore at
high frequencies, their separate indication is not really interesting
for RF exposure."
The distance at which the "near-field" can be calculated is given as a
formula, and is dependant on the frequency. Speed of light (C in m/s) /
frequency (Hz) = wavelength (m)
Then multiply Wavelength x 10 = close-up range, inside of which,
measurements are not accurately possible.

For a 900 MHz cell phone, that is a wavelength of 0.33 meters, so inside
of 3.3 meters (10.8 feet), the magnetic and electric fields are *not*
coupled to each other, and must be measured separately.

Still learning...
Stewart


S Andreason wrote:
> So In this case, the Magnetic part of the name refers to the process
> of creating the RF, and not inferring the magnetic field extends for
> miles.
>