# RF transmission based in magnetic field only ?

Discussion in 'General Electronics Chat' started by Externet, Aug 15, 2016.

1. ### Externet Thread Starter AAC Fanatic!

Nov 29, 2005
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Hi.
Could a 10 MHz RF signal propagate only with its magnetic field and without its electric field, from/to a 'ferrite' type of antenna ?
-Say the RF electric field is severely attenuated by the propagation medium, but its magnetic field is not-

2. ### nsaspook AAC Fanatic!

Aug 27, 2009
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If you mean far-field in air or vacuum the answer is no. Near field can be mainly induction so strictly magnetic coupling is possible as we see in most wireless power devices. EM radiation is relativistic phenomenon so magnetic fields may be viewed as relativistic distortions of electric fields not independent forces. So if either field is severely attenuated (not just transformed) by the propagation medium the sum total of RF energy is lost during that process.

3. ### Papabravo Expert

Feb 24, 2006
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Actually Maxwell's equations make this an extremely challenging proposition. In short, any changing electric filed produces a magnetic field; and any changing magnetic field produces an electric field. Since these are VECTOR fields the word "change" applies to BOTH the magnitude AND the direction. The process of modulation implies change, so I would have to say that if it were possible there would be NO information in the signal.

4. ### panic mode Senior Member

Oct 10, 2011
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just start by making your own magnetic monopole, after that nobody can tell you what you can and cannot do

5. ### MrAl AAC Fanatic!

Jun 17, 2014
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Hi,

First, the Poynting vector shows that if we reduce either field then the total energy is reduced also. This means that if E was reduced then we'd have to increase B. However, if E was reduced to zero, then no amount of B could transfer any energy, so there would have to be at least some E left.

It's almost like current and voltage where P=I*V. If we reduce V then we reduce P so it takes more I to make up the same power.

You could look up the largest electromagnet ever made and think about how far it might send a signal to a remote location.

In classical theory the signal travels outward forever but it decreases so fast that it makes it impractical to detect at some distances far from the source.

Mar 9, 2015
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