RF blocking stickers for cell-phones

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In summary, RF blocking "stickers" for cell-phones are a popular but questionable product that claims to protect users from harmful radiation emitted by cell phones. These stickers are small, perforated stickers that are placed over the speaker holes of the phone. However, there is no scientific evidence to support their effectiveness and they are seen as a scam by many. Additionally, the majority of EM radiation is emitted during transmission, so even if the sticker did block some radiation, it would also decrease the phone's range.
  • #1
xykotik
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RF blocking "stickers" for cell-phones

I still see these things around! It drives me nuts that I even have to explain it to people, but it's so hard to cover my judgemental feelings toward the lunacy (and outright fraud) with a kind semi-technical explanation that I think they just shut me out.

I was hoping to find a nice website with maybe some illustrations. Has anyone seen such a thing? I hope I didn't overlook it in this forum. I suppose I could get motivated and do it myself, but it is more productive to not duplicate effort, and there has to be something out there already.

(oh yeah, they usually come with the "range-extender" sticker to put on your battery. AHHH!)
 
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  • #2


I work for a mobile phone company. I'm now in sales but began as a technician, repairing faulty/damaged handsets. You wouldn't believe how many of those damn stickers I saw on people's phones.

Whenever a customer asks me if they work, I respond by reminding them that millions of dollars of research by scientists go into design and testing of the handsets, and if a little foil sticker really aided their operation, they'd come pre-installed from the factory :)
 
  • #3


Perhaps you could start with a description of exactly what it is you're talking about for those of us who apparently live under a rock.

What stickers? What do they do?
 
  • #4


DaveC426913 said:
What stickers? What do they do?

http://blockcellphoneradiation.com/ [Broken]. They do exactly what you expect them to: separate retards from their money.
 
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  • #5


I think it's getting crowded under this rock, Dave. I've never heard of these stickers either.
 
  • #6


negitron said:
http://blockcellphoneradiation.com/ [Broken]. They do exactly what you expect them to: separate retards from their money.

LOL! Wow, people pay $20 for a sticker? (Yes, I had to click the "add to cart" button to find out how much they cost...always a sure sign of a scam.)
 
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  • #7


I don't use one on my phone but I would love to find out how much it affects the field strength. If someone has a sticker and access to a field strength meter or even a spectrum analyzer, would you make some comparative measurements and post the results here? My guess is that it not only acts somewhat as a shield but also changes the impedance of the antenna and causes some of the signal to be reflected back to the phone.
 
  • #8


skeptic2 said:
I don't use one on my phone but I would love to find out how much it affects the field strength. If someone has a sticker and access to a field strength meter or even a spectrum analyzer, would you make some comparative measurements and post the results here? My guess is that it not only acts somewhat as a shield but also changes the impedance of the antenna and causes some of the signal to be reflected back to the phone.

I don't think it'll do anything. If you check out the site negitron linked to, they are just little perforated stickers that fit over the earpiece part, nowhere near the antenna.
 
  • #9


Just to be Devil's Advocate, what is your evidence that they do not work?

I'm not doubting that they don't; I'm sure they don't, but can you show it? We can't accuse others of succumbing to myth or to common-sense or gullibility if we don't have evidence-based facts behind us.

[ EDIT ] OK, first point I grant: radiation does not come out of the speaker holes.
 
  • #10


Radiation-blocking stickers aside, there's something I've never understood about this whole 'don't hang it on your belt' thing.

A phone that is receiving a signal is not an EM radiation source. It is simply processing the ambient radio signals in the atmo.

A phone that is sending a signal is an EM radiation source. But it is not on your hip; it's on your face.

So, before anything else is said and done, how does a phone on your hip expose you to dangerous EM radiation?
 
  • #11


DaveC426913 said:
So, before anything else is said and done, how does a phone on your hip expose you to dangerous EM radiation?

Phones periodically contact the local tower to let it know its there.

As for the sticker, they do nothing. Its 100% scam. the lion's share of EM fields is in the transmission, itself. So if the sticker DID block anything notable, it would also reduce the range of the phone.
 
  • #12


DaveC426913 said:
So, before anything else is said and done, how does a phone on your hip expose you to dangerous EM radiation?

A phone that's turned on will periodically send out a locational signal so the network knows where the phone is in order to route calls most efficiently. Also, when the phone rings for an incoming call, it sends out an acknowledgment signal so the network knows the phone is on and is receiving the signal.
 
  • #13


I assumed the don't hang it on your belt thing was since people started using those bluetooth things, so your phone is still on your belt while in use. Though, I'd think it would be better on your belt than in your pocket. Guard your gonads guys! :biggrin:

I was expecting this to be something that goes over the antenna, or wraps around the whole phone like a cover or something. Something that is only big enough to cover the speaker holes, and still has holes in it leaves me wondering how people fall for it. Maybe they just like the gold or silver stickers and think of it as "bling" for their phones, not so much thinking it works?
 
  • #14


Moonbear said:
Something that is only big enough to cover the speaker holes, and still has holes in it leaves me wondering how people fall for it.
Perhaps people have become comfortable with their microwaves, which need only a mesh to block radiation.
 
  • #15


I assumed the OP was talking about these, which were much more popular to see on peoples' phones in the repair shop than the 'radiation blockers':

http://www.shopcell.com/images/ABS.JPG [Broken]

The claim is that they will boost your signal.
 
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  • #17


DaveC426913 said:
Radiation-blocking stickers aside, there's something I've never understood about this whole 'don't hang it on your belt' thing.

A phone that is receiving a signal is not an EM radiation source. It is simply processing the ambient radio signals in the atmo.

A phone that is sending a signal is an EM radiation source. But it is not on your hip; it's on your face.

So, before anything else is said and done, how does a phone on your hip expose you to dangerous EM radiation?

Actually, mobile phones are not passive. They 'ping' the network on a schedule called a 'slot cycle' which is usually every 1-5 seconds or so to check for incoming calls, messages, etc. On some phones, you can access a hidden programming menu that will allow you to manually change the slot cycle index - you can raise it so only pings, say, every seven seconds which will improve your battery life, but if a call comes in, your phone might not start ringing for up to seven seconds. The phone doesn't know it has an incoming call 'till it checks.

Pagers are passive, though.
 
  • #18


Those stickers may also cause shorter battery life. If they reduce both the radiated and received signal strength then the base station will tell it to turn up its power to compensate.
 
  • #19


Moonbear said:
LOL! Wow, people pay $20 for a sticker? (Yes, I had to click the "add to cart" button to find out how much they cost...always a sure sign of a scam.)

Wow. Just like 7-11 and gasoline station mini-marts.
 
  • #20


Anticitizen said:
They 'ping' the network on a schedule called a 'slot cycle' which is usually every 1-5 seconds or so to check for incoming calls, messages, etc.

I don't get it. My mobile lies on my desk now. In fact, my mobiles were lying in more or less the same position for at least 9 years (I have moved here in 2000). It happens that whenever they contact the net I can hear the static in my computer loudspeakers - I know about incoming call/SMS few seconds before the mobile starts to ring. I can also hear my mobile contacting the net to confirm its presence. It doesn't happen every several seconds, more like every several hours.

Googled "slot cycle" and found this information:

The slot cycle index determines how often your phone will "wake up" and listen for any incoming calls and other info. If the SCI is 0, your phone wakes up every 1.28 seconds, if it's 1, every 2.56 seconds, 2, every 5.12 seconds and so on.

This is not phone pinging the net, this is phone waking up to LISTEN to the net.
 
  • #21


xykotik said:
(oh yeah, they usually come with the "range-extender" sticker to put on your battery. AHHH!)

You may add flashing stickers to the idiotic things that will shorten your mobile range.
 
  • #22


Anticitizen said:
Here is a randomized, double-blind, placebo-controlled test of the 'booster' sticker:

http://www.andybrain.com/extras/cellphone-antenna-booster-sticker-review-and-test.htm

According to the study: "Because your cell phone is a two way radio the sticker would also negatively affect the transmission properties of your phone by simultaneously adding resistive, inductive, and capacitive impedance to your outgoing signal (translation: smaller transmitted signal)."

Since the sticker is not connected to the phone's electronic circuits, how can it add resistance, capacitance, or inductance?
 
  • #23


Moonbear said:
I was expecting this to be something that goes over the antenna, or wraps around the whole phone like a cover or something. Something that is only big enough to cover the speaker holes, and still has holes in it leaves me wondering how people fall for it. Maybe they just like the gold or silver stickers and think of it as "bling" for their phones, not so much thinking it works?

Interestingly, a "sticker" coated with metal and covering the entire phone would actually work. It would work so well, in fact, that the phone will fail to receive any incoming calls. Next time somebody talks about a RF-blocking sticker, just tell them to wrap the phone in aluminum foil and leave a tiny hole open; the foil would act as a partial Faraday cage, blocking all but a tiny portion of the microwaves coming in and out.
 
  • #24


ideasrule said:
According to the study: "Because your cell phone is a two way radio the sticker would also negatively affect the transmission properties of your phone by simultaneously adding resistive, inductive, and capacitive impedance to your outgoing signal (translation: smaller transmitted signal)."

Since the sticker is not connected to the phone's electronic circuits, how can it add resistance, capacitance, or inductance?

Actually it can do all of the above by reflecting part of the transmitted signal back into the antenna. Depending on the phase of the reflected signal, the antenna will appear to have a different complex impedance.
 
  • #25


skeptic2 said:
Actually it can do all of the above by reflecting part of the transmitted signal back into the antenna. Depending on the phase of the reflected signal, the antenna will appear to have a different complex impedance.

I get that: the sticker reflects the signal, which is out of phase with the original signal, so the two will interfere and partially cancel. However, what does this have to do with resistance (voltage vs. current relationship), inductance (tendency of a coil's magnetic field to hinder change), or capacitance (tendency of a capacitor to resist AC current)? I'm not trying to be difficult here; I'm genuinely trying to understand the physics behind this.
 
  • #26


ideasrule said:
I get that: the sticker reflects the signal, which is out of phase with the original signal, so the two will interfere and partially cancel. However, what does this have to do with resistance (voltage vs. current relationship), inductance (tendency of a coil's magnetic field to hinder change), or capacitance (tendency of a capacitor to resist AC current)? I'm not trying to be difficult here; I'm genuinely trying to understand the physics behind this.
For one, the magnetic field generated applies a resistive effect on the current flow.

Same thing that limits amperage in a long, coiled extension cord. The current flow through the cord creates a magnetic field. The magnetic field opposes the current flow.
 
  • #27


ideasrule said:
I get that: the sticker reflects the signal, which is out of phase with the original signal, so the two will interfere and partially cancel. However, what does this have to do with resistance (voltage vs. current relationship), inductance (tendency of a coil's magnetic field to hinder change), or capacitance (tendency of a capacitor to resist AC current)? I'm not trying to be difficult here; I'm genuinely trying to understand the physics behind this.

You're right, we should be careful when referring to the effect of a nearby element as simple reactance. Only when we can rightly normalize a phase outside +/-180 degress to within +/-180 degress, can we say there is simply reactance. Specifically, its OK to do that if the parasitic element is well within the modulation length (where modulation length is the shortest distance containing a continuous wave carrier). So its typically OK for narrow band systems to think of the various parasitic elements in an antenna (even those several carrier-wavelengths away from the driven element) as simply contributing so much reactance to the antenna impedance, because those phase values outside +/- 180 can rightly be normalized within +/-180 degrees. I believe this is the case with a metal strip on the surface of a cell phone.

However your point is well taken, because one cannot do this for an ultra wideband system, for example. An antenna with parasitic elements a notable fraction of the modulation length away from the driven element will distort the modulation. But cell phones are not UWB, of course.
 
  • #28


negitron said:
http://blockcellphoneradiation.com/ [Broken]. They do exactly what you expect them to: separate retards from their money.

LOL!
Waveshield radiation blockers are made from a material discovered by the owner of the company while he was on a trip to Asia.
They're made from Asian Hashish?!
 
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  • #29


ideasrule said:
Interestingly, a "sticker" coated with metal and covering the entire phone would actually work. It would work so well, in fact, that the phone will fail to receive any incoming calls. Next time somebody talks about a RF-blocking sticker, just tell them to wrap the phone in aluminum foil and leave a tiny hole open; the foil would act as a partial Faraday cage, blocking all but a tiny portion of the microwaves coming in and out.

Better yet, put the tinfoil over your head, to protect yourself from other people's cellphone radiation (also alien signals and government mind-controll rays).
 
  • #30


Its a sound plan, since the brain is an electromagnetic organ.
 

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