Eliminating radio interference from Apple charger • Hacker News Board

Re: Eliminating radio interference from Apple charger

#91

Post by skykooler » Wed, Oct 04, 2023, 11:06 PM UTC

jrockway wrote: post #77

t0mas88 wrote: post #75

Earlier quoted context omitted.

Near-field being as big as 2 meters from the charger can be quite relevant for use in aircraft. Since on a narrow-body aircraft passengers can easily be within 2 meters of some of the VHF antennae. On the other hand, aviation voice radios aren't very sensitive and navigation radios have filtering built-in. So the output of an Apple charger is probably some orders of magnitude too small to cause any issues.

> Since on a narrow-body aircraft passengers can easily be within 2 meters of some of the VHF antennae. But, separated by a very large piece of conductive metal. (I think even carbon fiber planes have a conductive layer in there, to prevent damage from lightning strikes.)

Isn’t carbon fiber conductive itself?

Re: Eliminating radio interference from Apple charger

#92

Post by Aurornis » Wed, Oct 04, 2023, 11:11 PM UTC

threemux wrote: post #40

OP appears to be Finnish judging by the OH callsign - perhaps his regulator cares about all the interference to the amateur bands from cheap electronic devices. As a fellow ham I can assure you that the FCC does not care about interference from these devices if they are only causing issues for amateurs. If all the cheap switching power supplies and other devices were actually tested, almost none of them would be RF q…

> As a fellow ham I can assure you that the FCC does not care about interference from these devices if they are only causing issues for amateurs.

This isn’t true at all. FCC would care greatly if a company the size of Apple was selling a product that violated the emission limits.

That said, I don’t think this device violates the official limits. The author’s problem is that they need something extremely quiet, beyond the acceptable limits.

> If all the cheap switching power supplies and other devices were actually tested, almost none of them would be RF quiet (or even compliant).

If you’re suggesting that “almost none” of the power supplies on the market are actually compliant, you are incorrect. I’ve done my fair share of compliance testing. It’s true that you can find random supplies that aren’t compliant, but it’s not true that we’re all out here fudging test results and lying our way through certification. These things actually get tested.

Re: Eliminating radio interference from Apple charger

#93

Post by Aurornis » Wed, Oct 04, 2023, 11:14 PM UTC

hulitu wrote: post #7

> Eliminating Radio Interference from Apple Charger Why not notify the FCC ?

Because it probably isn’t violating the FCC limits. Looking at the chart he shows, there isn’t much power coming out.

The author’s use case is relatively niche. The FCC limits aren’t designed to be so strict that devices can’t emit measurable radiation at all because that’s an impossible task.

The only reason the author is hearing it is because he is literally tuning a highly sensitive radio to that frequency and putting it right next to the device.

Re: Eliminating radio interference from Apple charger

#94

Post by Aurornis » Wed, Oct 04, 2023, 11:16 PM UTC

NegativeLatency wrote: post #2

I wonder if someone suggested this at apple and was overruled because a bulky ferrite would "look bad"

Why would Apple (or any company) put a ferrite on the cable if it wasn’t needed to pass FCC?

Expecting every company to make their products ultra-quiet beyond the FCC limits so amateur radio operators can use them right next to their radios isn’t realistic. You certainly wouldn’t like paying the added costs of all of your products just to make them extra quiet for hams.

The author showed how easy it was for hams to solve their own problem as needed. Putting a ferrite on every charger in the world just to appease the handful of hams who want to use their radio right next to it is unreasonable.

Re: Eliminating radio interference from Apple charger

#95

Post by Aurornis » Wed, Oct 04, 2023, 11:17 PM UTC

oherrala wrote: post #8

dangus wrote: post #5

Earlier quoted context omitted.

Honestly, I’d rather my electronics cause some noise on a frequency I never use than have a ferrite bead on every USB cable under the sun. Seems like the author resolved the problem at minimal cost and effort.

You can be using a device and it might not harm you personally, but it could harm anyone around you using these frequencies. This includes airplanes and ground control, and boats. Your device's interference could cause problems or even life threatening dangerous situations. That's why it's illegal in many countries to cause too much radio interference (there's always some).

> but it could harm anyone around you using these frequencies.

Not really. Part of the FCC certification process is that devices need to accept interference from other devices operating within the limits.

Go read the FCC sticker on the bottom of any nearby device if you don’t believe me. It’s spelled out in the text.

The only reason the author had a problem is they put it right next to, quite literally, a highly sensitive receiver tuned to the exact frequency. It doesn’t mean the device was exceeding FCC limits, it means the ham operator needed to carefully set up their environment more tightly then even the FCC limits.

Re: Eliminating radio interference from Apple charger

#96

Post by Aurornis » Wed, Oct 04, 2023, 11:21 PM UTC

JoeAltmaier wrote: post #89

I heard years ago, Steve Jobs wouldn't allow a choke on a cable because they looked bad. A chronic problem as long as Apple has existed?

No company is going to put chokes on every cable if they’re not needed to pass FCC. Why would they? Would you want extra chokes on every cable just in case a ham operator might use the product somewhere?

Note that this author isn’t claiming the device breaks FCC limits, just that it emits enough that his highly sensitive radio could pick it up.

It’s not reasonable to be mad at a company for shipping a product that meets the limits. This guy just wanted something lower than the official limits because he’s tuning a radio to that frequency right next to it.

Re: Eliminating radio interference from Apple charger

#97

Post by yreg » Wed, Oct 04, 2023, 11:22 PM UTC

JoeAltmaier wrote: post #89

I heard years ago, Steve Jobs wouldn't allow a choke on a cable because they looked bad. A chronic problem as long as Apple has existed?

Can you ELI5 how does this negatively affect the consumer and why should the consumer prefer the 'bad looking' choke option?

Re: Eliminating radio interference from Apple charger

#98

Post by galangalalgol » Wed, Oct 04, 2023, 11:26 PM UTC

colechristensen wrote: post #55

wkat4242 wrote: post #16

Earlier quoted context omitted.

Yeah and the external wire will act like an antenna especially if it's got the right length. Very bad. Strange also because Apple usually gets their PSUs made by Delta afaik and they are as good as it gets.

It’s not very bad. Detectable signals is not at all equivalent to interference. Folks need to relax. People actually experienced with RF wouldn’t worry about this at all, and the FCC is perfectly capable of doing its certification job.

When people ask for certification. The stuff you get on amazon now doesn't have FCC numbers. Or silk screening on the pcbs or components to identify them.

Also there was a possibly false tale of intel adding clock jitter years ago to spread the emi across a band to pass tests, and then forgetting to enable that jitter on production units.

Re: Eliminating radio interference from Apple charger

#99

Post by wglb » Wed, Oct 04, 2023, 11:40 PM UTC

genewitch wrote: post #66

gorkish wrote: post #45

I'm quite frankly amazed that this is the first time this guy has had to put a choke on something as a radio amateur. I guess he doesn't use HF that much otherwise he'd probably have opted to buy an entire bag of ferrites. Maybe his magsafe charger really is bad, but if it's plugged into a computer or a crap charger it's also likely that it's just RFI riding the cable straight out of the computer. USB stuff is the wo…

where can one buy a bag of ferrites?

Check out https://proaudioeng.com/fair-rite-ferrites/. Also dxengineering has them.

Re: Eliminating radio interference from Apple charger

#100

Post by threeio » Wed, Oct 04, 2023, 11:46 PM UTC

NovemberWhiskey wrote: post #76

amatecha wrote: post #71

Earlier quoted context omitted.

I use HF radio all the time from inside my home, in the middle of one of the densest cities in BC. Within the past few weeks I've made contacts with stations in Alaska, Belize, Costa Rica, Colombia, Russia and Japan with a radio inside my home in Vancouver, Canada. HF is 10000% usable in urban areas. It's not optimal or perfect, but it's just fine.

Sure. Right now, we're coming towards the top of a sunspot cycle that results in SFI levels not seen in 20 years. Let me know how you were doing in 2019. There's obviously a seasonal overlay here.

its still doable in 2019... just not as plentiful ;) I was still able to get DXCC during the lows in a Silicon Valley downtown tiny lot (however, this isn't an apartment in a major city)