Magnetic Field effect on Radio Waves (Wi-Fi Interference)

[Trevor Porter]

Hello Physics Forum! I'm in desperate need of proof that magnets or magnetic field will not effect the operation or range or wireless access (Wi-Fi). I have 1/2" rare Earth magnets within a metal housing every 5' within the same area as wireless routers and the customer is concerned that it will effect their wireless capabilities. I've need in the forums that magnetic field will not directly effect radio frequencies in classical physics (Quantum Physics need not apply). Can anyone provide documentation to support this from a credible source, such as textbook, university study, etc.? Thank you in advance!

 

[berkeman]

Hello Physics Forum! I'm in desperate need of proof that magnets or magnetic field will not effect the operation or range or wireless access (Wi-Fi). I have 1/2" rare Earth magnets within a metal housing every 5' within the same area as wireless routers and the customer is concerned that it will effect their wireless capabilities. I've need in the forums that magnetic field will not directly effect radio frequencies in classical physics (Quantum Physics need not apply). Can anyone provide documentation to support this from a credible source, such as textbook, university study, etc.? Thank you in advance!

Welcome to the PF.

What are the magnets for? If they get near any wireless devices, they certainly can affect the ability of the radio circuit to operate (by saturating inductors on those devices). But the magnets would need to come within a few cm of the device to have an effect.

DC magnetic fields do not interact with the RF EM fields used by WiFi (as long as the magnets are kept far enough away from the WiFi devices so that there is no degradation of the inductors in the devices).

 

[Trevor Porter]

Hi there! Thanks for the reply. The magnets are for supporting bundled cable to steel a steel support structure. They will never be within cm of the device, a the closest point would be 3-6" but typically would be multiple feet away. The difficult part is that I need documentation to present to customer to resolve their concerns of the magnets interfering with their Wi-Fi... Does it exist?

 

[berkeman]

Hi there! Thanks for the reply. The magnets are for supporting bundled cable to steel a steel support structure. They will never be within cm of the device, a the closest point would be 3-6" but typically would be multiple feet away. The difficult part is that I need documentation to present to customer to resolve their concerns of the magnets interfering with their Wi-Fi... Does it exist?

3-6" is pretty close, especially if the mobile WiFi device (a smartphone?) is moving past the magnet. In addition to inductor saturation concerns at close distance, the relative movement of the magnet and device induces voltages in the circuit loops in the device, causing temporary degradation of operation as the device moves by the magnet. If this is a rare event, then there will be no noticeable degradation.

BTW, if the magnets are well designed and are stuck to a ferrous metal, there is very little fringe magnetic field anyway. The bulk of the magnetic field is contained within the "magnetic path" through the magnet and the steel. Are these horseshoe magnets with the cable inside the U of the magnet? It sounds like the steel support structure will be the biggest problem for the WiFi reliability because of multipath issues anyway...

 

[Trevor Porter]

The 3"-6" is worst case and we will most likely be able to avoid being anywhere close to that proximity. The WiFi devices are stationary just as the magnetic supports are. The magnetic supports are enclosed in a metal cup but open to one side where they will attach to steel, then making them fully enclosed. These are small 0.5" flat disk rare Earth magnets. Again, I need some official document or something from a credible source detailing how magnetic field has no affect on radio waves? Is there a physics law that applies? It all comes down to the documentation...

 

[berkeman]

The 3"-6" is worst case and we will most likely be able to avoid being anywhere close to that proximity. The WiFi devices are stationary just as the magnetic supports are. The magnetic supports are enclosed in a metal cup but open to one side where they will attach to steel, then making them fully enclosed. These are small 0.5" flat disk rare Earth magnets. Again, I need some official document or something from a credible source detailing how magnetic field has no affect on radio waves? Is there a physics law that applies? It all comes down to the documentation...

A better choice for the magnets would be horseshoe or some other closed magnetic path geometry. That will contain the magnetic field, and will give a much stronger holding force for the same amount of magnetic material. It is generally bad design practice to have a magnetic field coming out of your device (think -- person leaning up against it with their wallet and magnetic stripe credit cards inside). Plus, if you use a closed magnetic field magnet geometry, that pretty much eliminates the need to come up with something that is going to convince laypeople that a DC magnet will not cause interference with RF transmissions.

http://cdn.onlinemarketinginstitute.org/blog/wp-content/uploads/2012/07/magnet_XSmall.jpg

http://www.magnetics-china.com/wp-c...nets02-China-Ningbo-Hilan-Magnets-Factory.jpg