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iPhone audio detectable with AM radio

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21–30 of 68 posts

Re: iPhone audio detectable with AM radio

#21

I'm surprised this wasn't discovered sooner. For a while, when I was working in Portland radio, there was an AM station that played recent indie releases on it. Needless to say, while it was the butt of countless hipster jokes, there was a sizable crop of people with both AM radios and iPhones on them, frequently operating at the same time.

It wasn't discovered because either it didn't happen or the person claiming such has a faulty device. The FCC would never allow these phones to be imported for sale if they were so sloppy in their emissions. The idea that there are millions of people out there listening to AM radio every day for hours at a time in cars and homes/offices in close proximity to iPhones but no one ever detected this before is laughable.

Re: iPhone audio detectable with AM radio

#22
Most likely not an FCC (EMC) issue. This sounds like direct inductive coupling from speaker D class amplifier output (or power, which would be worse, but not likely) circuit at Why it is not an issue, is that magnetic field decays really rapidly, (inversely proportional to the cube of the distance [1]) and thus is not a general concern. In fact some "secure by physics" nearby communication methods like RuBee [2] relay on this.

[1] https://en.wikipedia.org/wiki/Near_and_far_field

[2] https://en.wikipedia.org/wiki/RuBee

Re: iPhone audio detectable with AM radio

#24
post #20
post #10

Earlier quoted context omitted.

In a later tweet he says the signal is pretty strong and that he could detect it from 6 feet away

Going to have to call bullshit on this. If it was detectable at that range then he has a faulty phone. The iPhone is classified as an emitter and so it needs to undergo rather strict FCC testing to ensure that it does not emit outside of certain frequencies and at specific power levels. The device would NEVER have been approved if it emitted at this level into bands licensed to other uses.

6 meters is near field in that frequency range. The emission power is possibly well below FCC limits.

Re: iPhone audio detectable with AM radio

#25
post #10
post #5

This is not surprising. We’ve been using AM and FM radios to debug circuits for decades. They can pick up oscillations and instabilities. But the range is centimetres at best. So much so the antenna gets used as a fairly directional probe.

In a later tweet he says the signal is pretty strong and that he could detect it from 6 feet away

He said 20 feet away https://twitter.com/doctorcube/status/1301146339561164800

Re: iPhone audio detectable with AM radio

#26
Also happens in the reverse. growing up in the shadow of WTOP[1] towers in the DC area, we used to hear WTOP in our rotary phones (between dials mostly) and even sometimes picked up in our ovens (yes, could hear the radio coming out of the oven)

[1] https://en.wikipedia.org/wiki/WFED

it was really powerful, heck, I even remember in my youth going up to relatives in boston and being able to pick up the signal at night to listen to Oriole games in the summer.

Re: iPhone audio detectable with AM radio

#28
post #21

I'm surprised this wasn't discovered sooner. For a while, when I was working in Portland radio, there was an AM station that played recent indie releases on it. Needless to say, while it was the butt of countless hipster jokes, there was a sizable crop of people with both AM radios and iPhones on them, frequently operating at the same time.

It wasn't discovered because either it didn't happen or the person claiming such has a faulty device. The FCC would never allow these phones to be imported for sale if they were so sloppy in their emissions. The idea that there are millions of people out there listening to AM radio every day for hours at a time in cars and homes/offices in close proximity to iPhones but no one ever detected this before is laughable.

Arguments by appeals to authorities like the FCC, CDC, or FAA sort of work if the authority can be trusted.

For the argument to be coherent that trust must have been established by a proven track record of both employing the appropriate methods correctly and showing independence of vested interests in their reporting of the results.

Re: iPhone audio detectable with AM radio

#29
post #18
post #11

Earlier quoted context omitted.

Why would you assume that his experiences and yours are the same?

It’s physics. There is EMC testing done on these devices. There is little opinion involved in such matters.

You've clearly never done EMC testing, if you think there's no opinion involved in such matters.

You might as well say "It's software engineering. There's no opinion involved..."

Re: iPhone audio detectable with AM radio

#30
post #21

Earlier quoted context omitted.

It wasn't discovered because either it didn't happen or the person claiming such has a faulty device. The FCC would never allow these phones to be imported for sale if they were so sloppy in their emissions. The idea that there are millions of people out there listening to AM radio every day for hours at a time in cars and homes/offices in close proximity to iPhones but no one ever detected this before is laughable.

Arguments by appeals to authorities like the FCC, CDC, or FAA sort of work if the authority can be trusted. For the argument to be coherent that trust must have been established by a proven track record of both employing the appropriate methods correctly and showing independence of vested interests in their reporting of the results.

Apparently you have no idea what you are talking about, so you think that these sorts of arguments work when discussing FCC emission testing. The FCC does not actually run the test, they set the standards. The tests themselves are run by various labs and testing agencies that are certified to perform the tests and who would be risking a very lucrative gig for the sake of cheating on a test for a device that will be widely deployed and certainly tested by third-parties who will want to examine the device. It is possible for some mid-range device to slip through or bribe someone to pass a test, but unlikely to the point of absurdity that this would be done for something like an iPhone.
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