Low frequency magnetic communication

In summary: It just doesn't have a big effect. May be that low frequequency is required where wire dipoles would be very long indeed so loops are used.That may be part of it, but it's not the only reason. Low frequency magnetic fields also have some other advantages.
  • #1
enroger
12
0
In low freq magnetic communication, the carrier is not EM wave but low frequency varying magnetic field. Most of the energy is transmitted within the mag field, very little result in EM wave. I find this very strange, because in Maxwell equation's plane wave solution, B is always equal to E/c.

According to the link this site don't allow me to post(@$&^&*%), they do it by having the antenna a lot smaller than wavelength.

My question then is when is E = B/c valid? When not?
 
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  • #2
I suspect that what you're asking about is more commonly called Near field magnetic communication. From what I gather by Googling around a bit, you make the magnetic field around the transmitter oscillate in such a way that the far-field electromagnetic radiation (whose energy falls off as [itex]1/r^2[/itex] is negligible. Almost all of the energy goes into the oscillation of the near-field which falls off as [itex]1/r^6[/itex]. This gives a very short range, up to a couple of meters or so, which has advantages in some situations.
 
  • #3
Yes, that's it. This is just like an ordinary solenoid. What I don't understand is what determines you have far field or near field emission?

I mean with the plane wave solution B = E/c, and that any solution would be a superposition of plane wave solution, then there should be no near field, everything must be far field right?

Does it have something to do with the size of the antenna compared to wavelength?
 
  • #4
I have a question.
Does anybody research effect of magnetic field to the communication equipment (e.t. access point, subscriber module or something like that)?
Can you refer me on the link where I can find this information, please?

BR
 
  • #5
Induction or near field .. was soon abandoned in Marconi days.
 
  • #6
Could you be talking about the TTE (through the earth) wireless communication devices for communicating with trapped coal miners in mines several hundred meters below the surface? I believe these are near-field communication devices where the ratio of E/H is not important. Specifically the near field of a magnetic loop (dipole) will penetrate more than the near field of an electric dipole, just because of the electric field attenuation due to the electrical conductivity of soil and rocks. Google TTE emergency rescue communication.
 
  • #7
Not sure about that.

May be that low frequequency is required where wire dipoles would be very long indeed so loops are used.

The near field soon falls off with distance. It requires a proper EM wave to propagate over any distance even though magnetic loops are used as the aerials. I have used loops on the AM band broadcast band for long distance recpetion which can't be near field..not over a few thousand km.
 
  • #8
Maybe dipole made problem, because near dipole access point broke down to boot mode. Also near dipoles there are a lot of other radio and wireless equipment. Can you refer me on some literature or recommend me literature for this topic please?
 
  • #9
do a Google search on low frequency magnetic communication coal mine, and low frequency magnetic communication TTE
 
  • #10
enroger said:
Yes, that's it. This is just like an ordinary solenoid. What I don't understand is what determines you have far field or near field emission?

I mean with the plane wave solution B = E/c, and that any solution would be a superposition of plane wave solution, then there should be no near field, everything must be far field right?

Does it have something to do with the size of the antenna compared to wavelength?

That equation only applies to the far field. It doesn't mean there is no near field. There is.
 

What is low frequency magnetic communication?

Low frequency magnetic communication is a form of communication that uses low frequency electromagnetic waves to transmit information. These waves have a frequency range of 30 Hz to 300 Hz and are typically used for long-range communication in environments where other forms of communication, such as radio waves, are not effective.

How does low frequency magnetic communication work?

Low frequency magnetic communication works by using a transmitter to generate electromagnetic waves at a specific frequency. These waves travel through the Earth's magnetic field and can be received by a receiver at a distant location. The receiver then decodes the information embedded in the waves, allowing for communication between the transmitter and receiver.

What are the advantages of low frequency magnetic communication?

One advantage of low frequency magnetic communication is its ability to penetrate through obstacles and travel long distances. This makes it useful for communication in remote areas, underwater, and underground. Additionally, low frequency waves are less affected by weather conditions and can be used in areas where other forms of communication may be disrupted.

What are the potential applications of low frequency magnetic communication?

Low frequency magnetic communication has a wide range of potential applications, including communication with deep-sea vehicles, submarines, and underground mining equipment. It can also be used for navigation, geophysical exploration, and monitoring of natural disasters. In the future, it may also be used for communication with spacecraft and interstellar probes.

Are there any concerns about low frequency magnetic communication?

There are some concerns about the potential impacts of low frequency magnetic communication on wildlife and the environment. Studies have shown that certain marine animals, such as whales and dolphins, may be affected by these waves. Additionally, there are concerns about the potential interference with other forms of communication and navigation systems. Further research is needed to fully understand the effects of low frequency magnetic communication on the environment.

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