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A radio frequency exposure test finds an iPhone 11 Pro exceeds the FCC's limit

spectrum.ieee.org

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Re: A radio frequency exposure test finds an iPhone 11 Pro exceeds the FCC's limit

#21

Post by whatshisface »

krastanov wrote: post #13
jws wrote: post #4

Testing phones from 5 millimeters away from the body may seem close, but for anyone carrying their phone in a pocket, the distance is closer to 2 millimeters. Because wireless power falls off exponentially with distance, what might be a safe amount of RF exposure at 5 millimeters could be much higher at 2 millimeters. They mean to say that you should expect a power about 6 times higher, (5^2 / 2^2). This is rubbish.…

So it is doubly incorrect... They are completely misusing the word exponential to mean quadratic which is already incredibly annoying, but it is not even quadratic, it is constant.

Not squared, inverse square. That's faster than exponential.

Re: A radio frequency exposure test finds an iPhone 11 Pro exceeds the FCC's limit

#22

Post by cdelsolar »

oefrha wrote: post #17
theseadroid wrote: post #14

Earlier quoted context omitted.

I wonder if we shall take exposure density into consideration? If RF is emitted in all directions, the closer the phone to the body, the same amount of RF will be received by a smaller area of skin?

You’re still thinking about a point source, where the actual scenario is closer to two parallel plates, in which case the non-normal components cancel out, leaving only the normal component, except at the edges. The most basic example from electrostatics: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elesht.h...

I don't think the phone emits radiation from its entire body

Re: A radio frequency exposure test finds an iPhone 11 Pro exceeds the FCC's limit

#23

Post by AnimalMuppet »

whatshisface wrote: post #21
krastanov wrote: post #13

Earlier quoted context omitted.

So it is doubly incorrect... They are completely misusing the word exponential to mean quadratic which is already incredibly annoying, but it is not even quadratic, it is constant.

Not squared, inverse square. That's faster than exponential.

You may need to check your math. Inverse square does not fall off faster than exponential.

Re: A radio frequency exposure test finds an iPhone 11 Pro exceeds the FCC's limit

#24

Post by zwieback »

Are they talking about the radiation from the Wi-Fi or cell radios? I would think that modern phones have very low duty cycles on those radios. The other radiation, e.g. from the clocking of the circuits should be extremely low, otherwise our batteries wouldn't last so long.

Re: A radio frequency exposure test finds an iPhone 11 Pro exceeds the FCC's limit

#25

Post by phonon »

swiley wrote: post #12
pentae wrote: post #9

I suspect this has something to do with the inferior intel modem that was used during the Qualcomm debacle. One of the main advantages of the next iPhone will be returning to a Qualcomm modem that isn't rubbish.

While I’m not a fan of what apple did it’s a bit disturbing that there’s literally just one company making cellular modems for US devices and that this company is really very hostile to users and device manufacturers.

https://www.extremetech.com/extreme/302712-mediatek-announce...

Re: A radio frequency exposure test finds an iPhone 11 Pro exceeds the FCC's limit

#26

Post by Robotbeat »

landont wrote: post #6

> The SAR limit is primarily concerned with a phone’s thermal effects—essentially, the power is limited to 1.6 W/kg to ensure that no one is burned by using their phone. I should be worried about the heat generated from my phone? I thought maybe there was some issue with RF and my cells, but this seems like a complete nonissue to me. Am I being foolish for writing this off? The only time my phone is going to burn me…

Sunlight shining on one side of a cube-shaped liter of flesh would be 10W/kg or so on average (and about 100W/kg if we consider the top 1cm).

1.6W/kg is a conservative limit.

Re: A radio frequency exposure test finds an iPhone 11 Pro exceeds the FCC's limit

#27

Post by preinheimer »

1123581321 wrote: post #18
mfer wrote: post #11

> That said, while the Tribune and Penumbra both used off-the-shelf phones, the FCC largely tested phones supplied by the manufacturers, including Apple. This speaks to a method that can be used to game the system. What prevents manufacturers from providing phones that are somehow different from the off the shelf versions? I'm not suggesting that's happening here. Just that the testing process is easily hacked.

The manufacturer needs the phone certified in advance of shelf stocking. There is nothing stopping the FCC from confirming their test results with retail units. Plus, the risk from cheating is enormous. It’s a lot easier in the long run to just design properly working phones.

It didn't turn out to be easier to design a clean burning diesel.

Re: A radio frequency exposure test finds an iPhone 11 Pro exceeds the FCC's limit

#28

Post by xondono »

swiley wrote: post #7
jolmg wrote: post #3

Earlier quoted context omitted.

> This an advertisement for their RF phone cases This is on ieee.org. The article mentioned this[1] other test by the Chicago Tribune. This isn't purely an advertisement though it serves that purpose a bit. It's disputed because they only tested 2 iPhones. > There are reasons to take the results with a grain of salt, however. McCaughey clarified that Penumbra supplied RF Exposure Labs with one iPhone 7 and one iPhone…

A lot of these smartphones go through imperical tests in an anechoic chamber managed by a third party lab to see if they’re bellow the allowed levels in each band. That sounds hackish but (IMO) isn’t the end of the world. What weirds me out is that they’ll send them to these third party labs and repeatedly test some small number (possibly one) of devices until it’s right up against what’s allowed. That feels less tha…

The main problem with all this kind of testing is how little precision there is.

“Double the energy limit” sounds a lot, but for a lot of these labs that’s inside of the error range of their equipment.

Re: A radio frequency exposure test finds an iPhone 11 Pro exceeds the FCC's limit

#29

Post by RL_Quine »

cdelsolar wrote: post #22
oefrha wrote: post #17

Earlier quoted context omitted.

You’re still thinking about a point source, where the actual scenario is closer to two parallel plates, in which case the non-normal components cancel out, leaving only the normal component, except at the edges. The most basic example from electrostatics: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/elesht.h...

I don't think the phone emits radiation from its entire body

That's what the cuts around the metal band of the iPhone are for, to segment the edge into different tuned antennas.

Re: A radio frequency exposure test finds an iPhone 11 Pro exceeds the FCC's limit

#30

Post by krastanov »

whatshisface wrote: post #21
krastanov wrote: post #13

Earlier quoted context omitted.

So it is doubly incorrect... They are completely misusing the word exponential to mean quadratic which is already incredibly annoying, but it is not even quadratic, it is constant.

Not squared, inverse square. That's faster than exponential.

No. All polynomials and rational functions fall off drastically slower than exponential.
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