
A radio frequency exposure test finds an iPhone 11 Pro exceeds the FCC's limit - acdanger
https://spectrum.ieee.org/tech-talk/telecom/wireless/radio-frequency-exposure-test-iphone-11-pro-double-fcc-limits
======
jws
_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.

The square of the distance model is for a pair of points. Phones in pockets at
such closed distances are more closely modeled by a pair of infinite planes
where the power falls off not at all. The real result will be in between, but
very much closer to 1 than 6.

~~~
madengr
Well you are in the reactive near-field, so the antenna will de-tune, hence
the power amplifier won't see it's ideal match, and not deliver as much power.
All depends on antenna design and orientation, assuming they don't use active
impedance tuning.

The base station also tells the phone to back-off. If the TX were running at
full power, the battery will die quickly. Leave your phone in a metal,
security cubby and your battery will die quickly; no power control and worse-
case antenna loading.

Also the highly asymmetric data usage these days. Very little energy on the
uplink.

FWIW I design antennas and amplifiers for a living. The only time I'd worry
about RF exposure is to the cornea; that is a proven hazard. RF burns are a
right of passage for PA designers, and are harmless as it's the outer skin
layers.

~~~
johnr2
> RF burns are a right of passage for PA designers, and are harmless as it's
> the outer skin layers.

A literal example of skin effect?

~~~
madengr
Yep. Put your finger on the corner of the output coupling cap on a 50 Watt
S-band PA. It will turn your skin black from the charring, but doesn't
penetrate into the live tissue. Just don't leave it on too long.

Could probably gives non-permanent tattoos with this method.

------
landont
> 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 is if the battery explodes, which doesn't seem to be
a pervasive issue. So probably not. As someone else pointed out this is a
marketing ploy.

~~~
testvox
Some people do believe that non ionizing radiation has effects other than
those produced by the added thermal energy (or that the thermal effects are in
some way significant). The actual scientific evidence for this is minimal
though.

~~~
jcims
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4676010/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4676010/)

Essentially EM fields alternating in the low to medium frequency bands
(~100khz-1mhz) can disrupt cell processes by physically jiggling the polar
molecules that make up portions of miotic spindles/microtubules. Among
presumably other things this effect is being investigated as a cancer fighting
mechanism called 'tumor treating fields'.

The carrier frequency of mobile phones is obviously far beyond the range in
question, but there could be signal modulation components that alternate RF
power levels in this frequency range.

~~~
avian
If your phone emits any non-trivial amounts of RF power at 100 kHz-1MHz
frequencies, regardless of whether this comes from intermodulation products or
something else, it doesn't pass existing EMC regulations and can't be legally
sold to consumers.

This is something that is already (or should be, in theory) rigorously tested
for everything that's put on the consumer market (from your cheapest USB
charger to your iPhone).

~~~
lima
Not a given if said USB charger is cheaply produced in China.

~~~
avian
Yes, you can debate how much imported (or for that matter, domestically
produced) stuff is actually tested, but the fact remains that existing laws
and regulations do cover this, even if enforcement is maybe lacking.

~~~
lima
I'm an ham radio operator, and shortwave spectrum pollution is sadly a big
problem despite very strict regulations.

The unfortunate reality is that the market is flooded with noisy devices,
often cheaply produces overseas, that vastly exceed legal limits (chargers and
other rectifiers, plasma televisions, powerline adapters, and much more).

Enforcement is difficult due to how widespread these devices are.

In many places, the noise floor is to high that long-range shortwave radio
communications all but impossible.

~~~
zaptidizap
I think police cars should measure it.

~~~
lima
It can take hours to pinpoint the location of a specific transmitter with
skilled equipment operators.

------
zitterbewegung
This an advertisement for their RF phone cases. In the article the premise is
refuted.

~~~
jolmg
> 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 11 Pro for the tests—phones the company had purchased off
> the shelf. He attributed not testing more phones to the cost of purchasing
> multiple iPhones

This is also important:

> More notably, when the FCC conducted a follow-up investigation after the
> Tribune published its story, the agency did not find evidence that any of
> the phones exceeded SAR limits. That said, while the Tribune and Penumbra
> both used off-the-shelf phones, the FCC largely tested phones supplied by
> the manufacturers, including Apple.

It raises the question whether Apple and others supplied the FCC with phones
that are different from what they sell.

[1] [https://www.chicagotribune.com/investigations/ct-cell-
phone-...](https://www.chicagotribune.com/investigations/ct-cell-phone-
radiation-testing-20190821-72qgu4nzlfda5kyuhteiieh4da-story.html)

~~~
swiley
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 than scientific and probably
wrong although I’m not sure what I’d change.

~~~
deftnerd
The "conspiracy" portion of my brain makes me wonder if it's possible that
Apple phones have lower power levels if the location services determines that
the phone is in a location with a known anechoic chamber. There can't be that
many of them.

Such behavior has already been shown by automobile manufacturers during the
"diesel-gate" incidents.

~~~
swiley
You don’t have to do that, usually you’ll run special test firmware on the
device and say that this behaves appropriately (I’ve done this for other
companies)

Remember that this is fundamentally a legal/social thing that involves
engineering/science and not the other way around.

~~~
jjoonathan
Right, you're supposed to test to the worst case and you get to define "worst
case." Cheating would be as simple as defining a favorable "worst case."

Before the tin-foil crowd calls regulators stupid, I'd like to point out that
in the absence of cheating this allows hardware engineers to do a better job &
design a system that is robust to software shenanigans. That's a nice thing.
Maybe we cannot have nice things, but if so, let's prove it rather than
presuppose it.

I'd estimate the likelihood of cheating by looking to see if people are
choosing phones on the basis of EIRP the way they choose cars based on MPG. I
don't see that happening, so I estimate that the likelihood of cheating is
low, and would vote to keep the cooperative model around.

------
_bxg1
If the only possible negative effect is "burns", then it's easy to verify that
people all over the world aren't getting burned by their phones, no? Testing
and standards are still important, but it doesn't sound like there's some
nefarious hidden effect we may just not know about.

------
mfer
> 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.

~~~
1123581321
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.

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

~~~
toast0
VW (and others, historically) didn't make special vehicles to pass the test;
all of their vehicles would be expected to pass the test as administered on a
dynamometer and fail the test if administered on a road.

Designing to the test is different than carefully selecting (or altering) a
sample that passes the test.

------
rini17
To everyone who keeps repeating "it's non-ionizing radiation, so any other
effect than thermal is impossible":

1\. saying something is impossible is not a scientific statement

2\. RF is capable of specifically affecting enzyme reactions, random example:
[https://pubs.rsc.org/en/content/articlelanding/2014/nr/c4nr0...](https://pubs.rsc.org/en/content/articlelanding/2014/nr/c4nr00407h#!divAbstract)

~~~
willis936
This ignores the primary issue of needing empirical evidence before claiming
discovery. If non-ionizing radiation of a certain level is hazardous then it
is provable. Affecting enzyme reactions is an observed effect, but what is the
health risk?

~~~
rini17
We don't know yet, so.. better safe than sorry, no?

~~~
sneak
Imagine if we said this about the food that comes out of every new restaurant.

Risk management is more than just universal risk aversion.

~~~
rini17
Yes, at least in my country, every restaurant is subject to stringent hygiene
regulations and audits. Is it a problem for you?

------
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.

~~~
Jolter
Cell radios. The wifi is much lower wattage than cellular so its effects will
be marginal.

------
pentae
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.

~~~
swiley
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.

~~~
phonon
[https://www.extremetech.com/extreme/302712-mediatek-
announce...](https://www.extremetech.com/extreme/302712-mediatek-announces-
dimensity-1000-arm-chip-with-integrated-5g-modem)

------
8bitsrule
I was confused by the "3.8W/kg" number. This Chi Trib article helped: it
details "the federal safety limit, which is 1.6 watts per kilogram averaged
over one gram of tissue." and explains how a former Qualcomm engineer did the
testing.

[0] [https://www.chicagotribune.com/investigations/ct-cell-
phone-...](https://www.chicagotribune.com/investigations/ct-cell-phone-
radiation-testing-20190821-72qgu4nzlfda5kyuhteiieh4da-
story.html#nt=interstitial-manual)

------
sschueller
I have posted this in the previous post that came up about this but I am quite
concerned that the idustry may be currently self certifing its devices and
getting phones past FCC regulations that do not meet the requirements just
like Boeing and the FAA. We need proper funding for the FCC so they can do
that job and not some industry paid company with a conflict of intrest.

------
dieselerator
In my case the phone has never been in my pocket while in use. The phone may
occasionally ping the cell tower. Otherwise it is just listening in standby
mode, in plain words, not transmitting. The premise of the article is weak. In
my opinion the article was not suitably vetted by _Spectrum_.

~~~
kube-system
Plenty of people use hand-free devices with their phones in their pockets.
Many others hold the phone against their head when talking on it.
Additionally, there are many network-intensive applications which can be used
while the phone is in your pocket, i.e. mobile hotspot.

Probably the least common scenario is for a phone to be transmitting at full
power when it's _not_ in close contact with a human.

------
GnarfGnarf
EMR meters measure Volts/meter (V/m), milliwatts per square meter (mW/m²), and
milliGauss (mG).

How do you convert to watts/kilogram?

Maybe measure the surface of my cross-section, multiply by mW/m², divide by my
weight?

I have a Cornet ED88T, a GQ-390, and a Tenmars on order.

------
remote_phone
If the phone has a strong wifi signal but a very poor cell signal, will it
emit a lot of RF still?

~~~
Jolter
Yes, the wattage required to reach the cell tower is unaffected by wifi
coverage.

~~~
sudosysgen
If there is WiFi, the radios will be much much less active or even switch away
from LTE/5G.

------
chillingeffect
my father occupationally used to measure RF output from mountaintop cell
repeaters. he was always pushing back on operators for pushing just a little
outside the limits so they could pick up more calls.

~~~
nomel
I always assumed the phone to tower path would be the limit, not the tower to
phone.

~~~
moftz
Right, in most cases, whatever side of a comms link that is hooked up to mains
power isn't going that much about power usage. But there are limits on
broadcasting power from the towers so as not to cause problems with farther
away towers that want operate on the same frequencies. It's like how you
usually want to not be on the same Wifi channel as your neighbor. It's going
to take either more RF power to overcome their signal or take more time
getting data through due to a less than perfect signal quality. Cell towers
occupy a certain geographic cell so you want some overlap in signal between
neighbors but you don't want it to extend much further than what it takes to
leave enough time for someone in a car, for example, to have their
conversation handed off to the neighboring tower. Cell tower operators might
want to boost their signal power if they are bordering an area with low
coverage but it's going to begin to interfere with cells outside their
intended range. The FCC sets these limits for different applications and
frequencies. An FM radio tower is going to have a massive output power as
compared to a personal FM transmitter for your car and for good reason, no
else one wants to hear your shitty music.

