Ferrite beads block cell phone radiation?

Bead 'slashes mobile radiation'

Radiation from hands-free mobile phones can be reduced to virtually zero by a simple tiny magnetic bead which costs a few pence, a government adviser says.

Professor Lawrie Challis said clipping a ferrite bead on kits stops the radio waves travelling up the wire and into the head.

He called on the mobile phone industry to start using them "as standard".

The beads, which often measure less than 1cm in diameter, are commonly used to stop data interference in computers.

Professor Challis, who is chairman of the Mobile Telecommunications and Health Research Programme, told BBC News: "There is no evidence yet that mobile phones are harmful to health but people have not been using them long enough for us to be sure.

I agree they can have an impact. But the bigger issue is that mobile phones are tested to be comply with standards and have been passed safe
Michael Milligan, from the Mobile Manufacturers Forum

"Using a ferrite bead effectively reduces emissions to the head to zero but as yet manufacturers do not put them on hands-free kits."

And Professor Challis, who was also on the Stewart committee which looked into mobile phone safety in 2000, added: "I am not sure why, but I wish they would. They could use it as a marketing technique, you would think they would like to promote it."

While studies have shown hands-free kits reduce radiation, emissions still travel up the wires on the outside and are absorbed by the head.

The beads work by absorbing these "unintentional" emissions.

Wires

Dr Stuart Porter, of the department of electronics at the University of York, said he agreed with Professor Challis's comments.

Dr Porter, who has looked at the use of ferrite beads, said: "Hands-free kits effectively have two currents, an intentional one that stays within the wires and an unintentional one on the outside.

"It is the unintentional one the beads stop. They work by blocking the current, a bit like a block in a water pipe."

He said evidence suggested beads worked best when they were placed below the microphone on the hands-free kit, at about chest level.

But Michael Milligan, general secretary of the Mobile Manufacturers Forum, rejected Professor Challis's call for them to be used on hands-free kits.

"I agree they can have an impact. But the bigger issue is that mobile phones are tested to be comply with standards and have been passed safe."

Story from BBC NEWS:
http://news.bbc.co.uk/go/pr/fr/-/2/hi/health/4203077.stm
So how effective are these beads? Which dimensions would be optimal for radiation blockage?

I'm understanding that the article assumes that radiation from the cellphone itself would appear to be reduced because the user has a headset and so the phone would be distant from the body. So the ferrite bead is just blocking any residual radiation that might be travelling up the headset wire?

Thanks for your clarifications! :smile:
 
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How does this work?

My understanding of cell phone radiation is that it is transmitted from the antenna, and that a hands free set would not rebroadcast that radiation. Does anyone know what the exact mechanism for hands-free transmission of radiation is?
 
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The headphone jack being connected to the phone's circuitry cand and does transmit radiation. If your are familiar with some phones that have FM tuners built in you will note that they require you to plug in the headphone for the radio to work. This is because the headphones or earphones act like an antenna to capture radio waves and direct them to phone.

In the reverse manner when the phone is emitting radio waves (be it for FM radio or to communicate to the cell tower to make or receive calls) if the head phone jack is plugged in, the radio waves will travel up the head phone jack. this is not by design but non the less, this adverse affect causes the headphones to become a bidirectional antenna directing radio waves strait to the head.

It is also not safe to put the cell phone to your head when using it. using a ferrite bead or sometimes called ferrite choke on the headphone, placed as close to the cell phone as possible is the best alternative to not using a cell phone that I have found thus far.
 
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May be, we sometimes exaggerate some topics too much.

And take no notice of things like this.

But the thing is, if any type of radiations penetrate through your body, then I wonder what exactly happens in our body during this process. There must be some kind of danger.

I once read somewhere that if we use too much of cell phones, then our feet must have a direct contact with the earth during its use !!

Any idea how come ? !

:surprised
 

Hepth

Gold Member
437
39
It is also not safe to put the cell phone to your head when using it. using a ferrite bead or sometimes called ferrite choke on the headphone, placed as close to the cell phone as possible is the best alternative to not using a cell phone that I have found thus far.
But I thought that was what has been tested so far and there's no connection to any cancers or diseases? That's why it has been approved as safe. Claiming that it is "not safe" really does require some research and proof on your part. Do you have any links to studies concerning modern cell phones where it has been shown to be unsafe? If not, how then do you come to that conclusion?
 

mgb_phys

Science Advisor
Homework Helper
7,744
11
It is also not safe to put the cell phone to your head when using it.
If the 'researcher' believes that then they must believe there is some distance at which it is safe.
So having decided with no evidence that a phone next to your ear is dangerous, they have decided that one in your pocket is safe

Otherwise i can come along and with the same lack of evidence say that he shouldn't use a hands free set, because the phone is still within 1m of you, you should use a Bluetooth headset and keep the phone 10m away. Although I suppose you could claim that the radiation from the Bluetooth as harmful.
 
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For maximum effect the bead should be placed around the antenna at its base.
 

berkeman

Mentor
55,716
5,803
I once read somewhere that if we use too much of cell phones, then our feet must have a direct contact with the earth during its use !!

Any idea how come ? !

:surprised
That's false. At the wavelengths used by cell phones, their antennas work fine stand-alone.
 

Mech_Engineer

Science Advisor
Gold Member
2,569
169
My understanding of cell phone radiation is that it is transmitted from the antenna, and that a hands free set would not rebroadcast that radiation. Does anyone know what the exact mechanism for hands-free transmission of radiation is?
Do you understand the general principles of how a cell phone works in the first place? A cell phone uses a radio to communicate with a tower; a handsfree set (bluetooth) is ANOTHER radio that communicates with the cell phone (using a radio at a different frequency with much lower power).

But the thing is, if any type of radiations penetrate through your body, then I wonder what exactly happens in our body during this process. There must be some kind of danger.
Do you understand the difference between electromagnetic radiation like radio waves and ionizing radiation like X-rays and gamma-rays? I'll give you a hint- one can give you cancer, and the other has no measurable effect on you at all (that has yet been proven anyway).

A sweeping generalization like "radiation is dangerous" is meaningless, and driven by undereducation in the subject.

I once read somewhere that if we use too much of cell phones, then our feet must have a direct contact with the earth during its use !!
Let's just say that's excellent proof that you can't believe everything you read. Especially on the internet.
 
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Beads increase the impedance of the wire that threads through them at RF frequencies. Nowdays handsfree is going Bluetooth so this is becoming irrelevant.
 

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