Eliminating radio interference from Apple charger | Hacker News Reader

Eliminating radio interference from Apple charger

oh8hub.substack.com

283 pointsoherrala171 comments

> This radio interference was also present on the aviation frequencies (around 124 MHz)

How did this thing get FCC approval? What's it's FCC approval number? Who tested this thing? Want to look that up.

If RF got outside the charger and into the USB cable, it's very badly designed. The power in the USB cable is DC. There shouldn't be any significant RF component. There should be ferrite beads and capacitors in the power supply to deal with this. When the filtering is close to the switcher, it's much easier to deal with the noise, and very small ferrite beads, available in surface mount, can usually do the job. Once it gets out on an external wire, it's hard to filter.

This is an old problem for Apple. A report from 2013, from a pilot charging an Ipad in an aircraft.[1]

[1] https://pointsforpilots.blogspot.com/2013/06/radio-interfere...

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.

Breaking squelch on a scanning radio in the general vicinity is pretty bad. It shouldn't be generating such strong RFI on VHF frequencies. I use 2m (VHF) handheld radios at my desk at home with like 5 computers around me, countless chargers (including a wireless charger just like in the article). There is never a time that my radios are stopping on RFI generated within my office.

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.

I can't be sure this is the exact model as OP, but the FCC testing doesn't seem to indicate any issues from my brief skim:

https://fccid.io/BCGA2548

(I have not read the entire report and I have no expertise in RF.)

Is the original author certain he has an authentic Apple charger? I’ve seen teardowns many times of bogus Apple chargers that use worse designs and components.

http://www.righto.com/2016/03/counterfeit-macbook-charger-te...

Well, modern DC converters use PWM, and also the device in question is a Qi induction charger operating at 110 - 205kHz with up to 15W output so there is some significan- how are these unlicensed!?

>The power in the USB cable is DC. There shouldn't be any significant RF component.

Well that isn't even remotely correct.

Any time you have switching, which this does, in DC you have VERY high frequency components in every rise and fall time. Much faster than your period or switching frequency, it's all about how fast you rise/fall. You switch, rapidly, through anything that has inductance, and you have RF.

This, for reference see the book High Speed Digital Design by Hall Hall and McCall https://archive.org/details/highspeeddigital0000hall/ The sharper the edge of the digital pulse, the greater the strength of the AC high frequency components. A perfect square wave is the sum of the infinite series of odd harmonics of a sine wave with the same wavelength.

I watched a video recently that had another author describe issues in a way that I found very intuitive. https://www.youtube.com/watch?v=kdCJxdR7L_I

Even very expensive linear supplies will have Vpp of a few millivolts or microvolts "ripple". Vpp is voltage peak to peak, which you wouldn't expect on a DC device, but there you go.

i didn't read the article and i don't know the expertise of the author, but depending on the type of antenna you use, you may have to choke literally every wire in the "shack", KB/mouse, power, speakers, ethernet, etc. Although, funny enough, this is for the inverse case - the radio messing with the computer!

I wonder if an RF choke (AKA a 1:1 Current Balun) directly attached to the UHF port on the back of the radio would help in this circumstance - the feedline is probably coupling with the USB cable!

You don't have to let the spikes from the switcher get very far.

Here's the schematic for a switcher I designed.[1] This is a strange application - USB power in, 120V out, to drive an antique Teletype machine. Without any filtering, there would be huge spikes in the DC across C1-C2. But it didn't take much filtering to fix that. There's a small ferrite bead at L2, and an RC filter at the snubber at R1-C7. The back to back Zeners are to absorb inductive kickback from the output electromagnet. That's the output side. On the input side, there's more noise suppression, to prevent injecting noise back into the USB power source, which is usually a laptop here. Note L1 and C12. Those are all tiny surface mount parts, total cost in quantity maybe US$0.20.

It's an exercise in LTSpice to get the values right and make the DC power smooth DC, in both voltage and current. This is well understood.

There are radio hams using this thing, and they report it's not blithering in the RF spectrum.

[1] https://github.com/John-Nagle/ttyloopdriver/blob/master/boar...

Oooh. I clicked through your PCB there. I would highly recommend you read a couple books on circuit design. You have a 2 layer PCB with no ground plane and you aren't routing ground, signals passing parallel with each other on adjacent layers, you have mixed analog and digital domain, massively long traces where they could be shortened with a small jumpers.

Worst offender is you aren't using a ground plane or routing a return path. You might be under the impression that your signal travels on the copper you routed for the signal - it does not. It travels mostly in a magnetic field between your copper signal and the closest signal of largest difference. Which in your case is only sometimes going to be your ground trace.

Short version... I would not use this as any sort of example for RF performance, at all anywhere, ever, and I'm being a nice as possible on that. I bet if you made a quick loop with an oscilloscope it would off the charts in reality. This would never pass FCC background.

EDIT: I see this was 7 years ago, but I would not use that as an example. At a very minimum if you are still making circuits... Watch every Phil's Lab video from 1 to 100. But somewhere in 50s is a good one on stack ups and signal returns.

EDIT2: While I'm picking you apart, which you implictitly asked for, your board is HUGE. So who cares how large L1 and C12 are? On that note, I could almost not find L1 at all, the schematic is a bit of a mess. KiCad is great and now allows for global and bussed component blocks I would recommend. Again, there is a Phil's lab video on that.

Nothing there is going faster than about 300KHz, so the signal paths are not a big issue. If things had to go faster, there would be a proper ground plane. The tiny area around the switching IC did require careful layout (it just follows the Linear Technology data sheet) but the rest doesn't matter much.

There is no one ground. The 120VDC side has an HV ground, and the 5VDC side has a ground. The important point is to have separation between the two.

> nothing faster than 300k

That is exactly one of the misunderstandings I’m trying to warn that you are missing.

I’m certain that your switching transition times are massively faster than the 300k period (each rise and fall time).

You can have split grounds, but you don’t have traces under your grounds so in many cases you aren’t even effectively using them. You are grounding a portion of every signal inside every other signal trace.

“The rest doesn’t matter much”… my man, I can’t explain in this form just how wrong you are.

It’s one thing to be wrong on a design from years ago. My old designs were worse. But it’s another thing to willfully ignore all the ways in which someone who knows better is trying to help you with.

Everything you think about that circuit is wrong in ways you aren’t getting - yet.

Try Phil’s lab videos for EMI.

off topic, but what do you think of this video by Asianometry talking about the intricacies of analog design for a laymen audience? https://www.youtube.com/watch?v=lNypq1XuZRo

I disliked that video very much. It was FAR too long, talked about things like parasitic capacitance long before even getting near the topic of the video.

Then out of no where it's talking about tantalum nitride...

No, I'm pretty sure that video was made by an AI.

>How did this thing get FCC approval?

Looking at the radio display, it seems like the peak power is about 7-8 S-units. At VHF, that would be about -100dBm; or about 100 femto-watts. I presume that the charger is pretty near the radio. With free-space path loss being inverse square law, it's essentially going to be completely negligible within a very short distance.

Oh, and if the antenna is indeed near the charger (say within one wavelength, 2 meters in this case) it might be inside the near-field - which means that you're getting additional power transferred that wouldn't be reaching the far-field, and you might even be affecting the behavior of the device due to coupling.

Looking at the FCC report, the radiated emissions are totally in-line with FCC Class B requirements.

Modern ham radio equipment has exquisitely sensitive receivers and you easily hear all kinds of interference from digital devices that are completely Part 15 compliant. The prevalence of switched mode power supplies literally everywhere has made HF radio completely unusable for many people outside rural areas.

Do you have any idea how that power compares to regular FM radio broadcasts, which are somewhat close in frequency?

Is this something a regular radio would detect, or is OP just trying to listen to a handheld radio half a continent away using a really sensitive receiver with the volume knob turned all the way up?

To get a very broad idea: if you had perfectly efficient but isotropic antennas (you don't) this would be about the power level you'd get receiving a typical 3W hand-held radio signal at 140MHz from 1,000 kilometers away. This is why you can talk to the International Space Station easily enough with vanilla ham radio equipment.

Or, taking a notoriously powerful FM radio station like KRUZ 103.3, it would be like hearing that station from perhaps 300,000 kilometers away.

Most loss is not free-space loss though - it's due to reflections from man made objects and absorption into the earth that results in line-of-sight effects at these frequencies.

How did you come to that estimation? The strength of the RFI on the waterfall suggests received signal strength comparable to someone transmitting on a 5w HT within, say, 5-10 miles (aka not in the immediate neighbourhood, but pretty nearby). Someone transmitting 3w at 1000km distance will not register even the slightest on any amateur receiver, even with RF gain absolutely cranked to the max and with a massive antenna.

I actually updated my post about the same time you wrote this response; I was just considering free-space path loss, which is not where most of the loss is in typical ham scenarios. Most of the 5W in the case you described is getting lost in a terrible compromise antenna, then due to line of sight effects (assuming that the user is not standing on a hill or something) and multipath.

The ISS also orbits quite low. If you're relatively close to the path it's only a few hundred miles away. Small temporal window due to the speed, but still.

Due to proximity, the interference from the charger is comparable to what the receiver was expecting from a normal signal (like an amateur radio repeater or fellow operator's station), which is why his radio broke squelch while scanning. Because the radio is relatively close to the charger, the RFI is picked up quite well.

Comparing to a broadcast FM station, the strength of the RFI as observed by any nearby radio will be trivial by comparison. Broadcast stations are some of the highest-power radio transmissions around us, typically thousands of kilowatts (for example the rock station near me transmits at an ERP of 51,000 watts[0]). You will hear this station clearly no matter what kind of nearby RFI is present, and the receiver's AGC will reduce RF gain to probably as low as it goes. By comparison, amateur radios typically operate in the range of 5-100 watts. Thus you might gather that comparing localized RFI to broadcast stations is not a meaningful comparison.

[0]https://en.wikipedia.org/wiki/CFOX-FM

> Broadcast stations are some of the highest-power radio transmissions around us, typically thousands of kilowatts (for example the rock station near me transmits at an ERP of 51,000 watts[0]).

I don't think so.

Not "thousands of killowatts" transmitted. Your example is as you say, an ERP of 51kW.

But even ERP doesn't refer to the transmitter. An ERP of 51,000W is most likely a 5-10kW transmitter, with a gain factor of 5-10.

Back in the pirate radio days 100 and 250kw transmitters were common.

Back in the '30s a few AM stations ran at 500kw, and could be picked up on other continents.

AM? Definitely, but even that is 100, 250, 500. Not "thousands of kW".

Oh sorry, I doubled up my units of measurement there, yes, tens of kilowatts haha :) (unfortunately too late to be able to edit that comment)

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.

Oh man, I haven't been paying attention to the sunspot cycle. I got my license at a low and committed to being depressed about it forever, but ... time fixes everything I guess!

I wasn't an op in 2019 -- got my certification in 2022. That said, I used to receive FT8 with my RTL-SDR and have a few screenshots. Here's a map of my received signals on 40m, overnight in May 2020, with a random-wire antenna: https://i.imgur.com/flfyIZx.png At that time I lived in an even more densely-populated area (a condo complex with over 100 units, on a main street, surrounded by other similarly-large condo complexes).

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)

Making the contact is easy (the interference you hear doesn't exist at the receiver), hearing the other end is hard. Most of my indoor QSOs are people running 1500W FT8 which is ... an unnecessary amount of power. (Meanwhile, I'm sitting here transmitting at 3W.)

I often look at the automated reports and look sadly at the 99% of stations that can hear me but that I can't hear.

Yup, RX harder than TX in the city, that's for sure. I'm thinking to set up a "loop-on-ground" antenna[0] for RX which, from anecdotes I've heard from people I know, takes their S8 noise floor to like S1.

[0] http://www.kk5jy.net/LoG/

I should definitely set something like that up. I have a patio now and this would be unlikely to annoy anyone above me looking at my patio and reporting it to the board. (Not that I think my neighbors would care, but it's a common complaint against hams.)

Would not a persons specific setup have significant effect on the interference situation, - The radio would be in a completely shielded metal box? - so no interference that way directly , not via the antenna input. Outside antenna , with a shielded feed in cable would also reduce interference from these devices like small power supplies that just produce interfearance to a few meters distance ???

As someone who has always been interested in getting into ham radio - do you have any pointers on where to start or what to avoid?

Join a local club!

First of all, get your entry-level license. If you're in the US (or have someone who can receive mail for you), this is relatively easy and inexpensive, and can be done completely online.

Avoid sinking a lot of money into a transceiver immediately before you've been operating for awhile and know what you're really interested in doing. You also do not need a rooftop antenna for HF (3-30 MHz; the frequencies that most often travel far) - a wire across your backyard can be quite effective.

Since you're here, I recommend getting started with digital modes like WSPR and FT8. They require a lot less power to make some surprising connections, and will teach you a lot about how propagation works and adjusting antennas, and because of the low power requirements, can be done with relatively inexpensive equipment. Some "old timers" grouch about how they're not "real" ham radio, but ignore them.

Edited to add: A good starting point that doesn't even require a license is to get an SDR receiver like the RTL-SDR and hook a long wire to it as an antenna, then listen for WSPR or FT8 signals with WSJT-X, and whatever else (other digital modes, Morse Code) with fldigi.

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?

Carbon fibre is definitely conductive. A couple of years ago I measured a 1” diameter tube and got about 15ohms/ft.

Right, it's a resistor. This is a problem for airframes and wind turbine blades. Its resistance is too high to deal well with lightning. So aluminum is needed to provide a conductive path.

Yes, and blocks radio transmissions very nicely. When making a model airplane with a carbon fibre hull, we have to add a plain fibreglass or plastic window for the antenna to receive through.

>If RF got outside the charger and into the USB cable, it's very badly designed

Wouldn't this then be a problem with whatever car charger he is using and not with the apple device plugged into that charger?

> a pilot charging an Ipad in an aircraft.[1]

Fascinating. No wonders we have so much red tape on stuff that is in the air.

Could the problem be with the DC current that is being supplied via USB power from the car / power adapter? If this DC current is very noisy, then it could make the noise generated worse I presume?

Switch mode power supplies such as this one emit RF. There are varying degrees of shielding that can help, but ham radio stations that are looking for good reception forbid using any such chargers (e.g., iPhone charger, Macbook chargers, etc).

Far better to use a linear power supply, which has a transformer and as a result is far heavier.

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 worst offender in my shack -- the majority of USB cables are just a complete joke.

where can one buy a bag of ferrites?

There are several options from Amazon, try searching for "Clip-on Ferrite Ring".

I know; i hoped for a site that sells all the types of rings, binocular, clip-on - which are great for choking VHF vertical dipoles with the bottom leg being spokes that are obviously too short for the frequency - i digress.

I'm also just grown weary of amazon.

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

Type 31:

> Mix 31 excellent for 1-10 MHz common mode suppression, then about same as 43 up to 250 MHz, NOT recommended for multi-ratio impedance transformers (baluns/ununs) due to material characteristics and power handling capability – ok for ham radio 1:1 feed line choke applications. Curie temperature >130 C

But in looking for concise relevant information i found https://palomar-engineers.com/ferrite-products/ferrite-cores... which i quoted above

edit: also, thank you

Another way to get a lot of ferrite cores for super cheap is to harvest them from cables that included them like VGA and DVI cables. you can cut them out and peel off the overmolding. Most are still split core. The material is often not very good at lower frequencies like HF, but you can use more cores or loop your cable through multiple times to increase the effectiveness of the choke.

ha! No doubt - HF user here with a bag of ferrites.

When I'd transmit on 20m, it would sometimes open my old liftmaster garage door. Until I wrapped all of its cables in ferrites.

Can’t wait for his post after he ditches the HT in the car and buys a mobile unit to mount in it. He’ll be in a new world of hell.

I see something that looks like a MagSafe puck with a black plastic piece snapped on for some reason.

Are we sure it’s a real MagSafe puck? The article didn’t check that.

Sadly copies of Apple stuff are so rampant, especially on Amazon, if you didn’t buy it yourself from a reputable retailer. It’s quite possible it’s a fake. The little white charger bricks were copied rampantly. With Apple’s prices the fakers stand to make a lot.

Given Apple’s normal engineering quality that would be my first guess. Or Bloggie’s guess it’s the PSU that’s the issue.

It’s interesting they found the problem, and that a simple ferrite bead fixed it.

But I have no doubt there are fakes out there for something g like the MagSafe puck. Without ruling that out simply declaring it a “piece of crap” seems unwarranted.

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 quiet (or even compliant). However the large majority of the public is not impacted by these things and so there is no real constituency to get something done.

> 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.

That's... not a magsafe charger? That's a USB-C NFC charger. By all means show it's shit in every possible way but let's not grace them by acknowledging it has anything to do with magsafe. That's a Applified Qi charger.

MagSafe® is a registered trademark of Apple Inc., so if they call it a MagSafe® charger, it's a MagSafe® charger.

https://en.wikipedia.org/wiki/MagSafe_(wireless_charger)

Gonna hit back with "nope".

If Kleenex gets into toilet paper and tell you that toilet paper is now kleenex, the response is "you clearly don't what what the hell you're talking about, get your head out your ass".

Magsafe is a magnetic power connector that clicks into a socket, whether Apple sticks their head up their ass or not.

> Magsafe is a magnetic power connector that clicks into a socket,

Wikipedia on MagSafe (wireless charger)

> MagSafe is a proprietary, *magnetically attached* wireless power transfer

That probably means I can talk with my phone while wireless charger hangs on to the back of the phone?!

Yes, you can. I have double-sided tape under mine to keep it on my desk, otherwise you pick both up. I really like them stuck-down, I use one on my bedside table and one on my desk.

Are you saying that it’s a counterfeit? Apple sells this as a MagSafe charger: https://www.apple.com/shop/product/MHXH3AM/A/magsafe-charger

I own a MagSafe charger and unless the author added a third party black case (?) around the puck, then that’s not a real MagSafe charger. I haven’t heard of cases for it but that doesn’t mean they’re not common, of course.

From the article: "However, I have already bought this product and the other pieces for my car mount."

The black ring is probably one of the "other pieces for my car mount".

Yep, it looks like a knockoff.

How are you determining this?

MagSafe is simply Apple’s brand name for chargers that “plug in” via a magnet. It used to just be the ones that charged laptops, but now that iPhones have the magnetic ring on the back for specifically this purpose, there are MagSafe iPhone chargers out there too.

This thread looks like a relevant one to mention an issue with the Mac Studio that causes large inrush currents when you plug it in. The power connector arcs badly enough to trip a domestic 30mA RCD, it's reproducable with several units and on different electrical circuits at both home and office.

I noticed exactly the same thing on a new Mac mini M2 base model when I conncted the power cord. Now I'm relieved that it seems to be a common problem.

I don't know anything about electronics. Do you think this is some kind of defect or bad design of the power supply?

Apple is very generous on input capacitors for their power supplies. It's usually a sign a good design as it's one of the first places companies skimp; and ensures that even dirty wall power or highly spiky load will not trip the PSU and keep the computer fed. However, it is widely recognized that Apple overdid it on apple silicon macs. Like, they really should have skimped a bit on that one. (we have racks full of M1s at work, and boy powering the rack on is a pain due to the inrush)

Using too large input filtering capacitors without a soft-start circuit is a sign of very poor circuit design.

What size are the capacitors?

The arcs have nothing to do with tripping the RCD part of your breaker. The RCD part only trips on a substantial current (>30 mA, or less for specialty devices, or more for upstream RCDs) between hot and ground, it doesn't care at all about the current flowing between hot and neutral.

That inrush current however, given sufficiently large buffer capacitors, can be enough to trip the overcurrent protection that most if not all RCDs also have - and that one tends to get more sensitive as they age, it's a common issue with old breakers.

(Another device that could trip is an arc-fault detection device, but AFDDs are fairly new and not required by many electrical codes. Nevertheless, it's a good idea to upgrade your distribution boxes with them, if you have the budget. These things save lives.)

The Mac Studio has a 3-pin earthed C5 connector. I presumed it's not overcurrent as it trips a 32A type C RCBO in an instant.

Either way, it's certainly a problem with the computer - I've far more demanding equipment that has never done this, and have yet to find a circuit it won't *pop*.

That is not how an RCD works. It doesn't even look at ground.

An RCD will trip when the difference between the current going down the live and neutral conductors exceeds a certain value -- in normal operation they are opposite and cancel each other out.

If it operated how you describe, it could never detect someone touching a live conductor, because the current would not return through the ground prong.

Tangent- I had a similar problem in my undergrad EE capstone class where our serial connection to our microcontroller kept being filled with random garbage. I moved my laptop at one point - and it stopped! The charging cable had been lying across the wires for the serial bus, and apple chargers talk to their laptops over a serial protocol as it turned out. We were picking up crosstalk!

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.

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

Ferrite chokes are large and heavy. They're also not free. So the product costs more, weighs more and gets bigger.

Sounds like I'm with Steve on this one.

Yeah. Who needs a usable RF spectrum when iphone has interwebs?

Not only does the device feed high-frequency signals into your power wiring, it can get noise from it like motors turning on or off and spiking the voltage.

It's only a problem if it's a problem. If they'd done proper filtering inside the device maybe it's ok.

Once upon a time, when I was working at Broadcom, I put on a nice demo for some colleagues.

I had a long serial line strung across my desk from a USB-Serial dongle to an embedded board. It ran under the LCD monitor. Weird banding and noise was showing on the monitor.

The demo was: "watch the artifacts on the monitor go away, as I clamp this ferrite bead around the serial cable".

The poster's assumption that this is caused by the Apple product could be incorrect. The emissions could be caused by the supply equipment noise propagating down the cable. The load presented by the Apple product could induce the supply equipment to emit noise at that frequency.

I'd be much more enclined to blame the cigarette lighter to usb adapter used in the car instead of the magsafe adapter. apple usually do their homework.

> Eliminating Radio Interference from Apple Charger

Why not notify the FCC ?

There is a big possibility the author just bought a counterfeit, AFAIK all consumer electronic devices have standard EMC compliance requirements, these spikes showed should be easily observed in the 10M chambers during testing.

The device was ordered from Apple's website.

The issue could be coming from the AC-DC charger used with the MagSafe charger as well, maybe retest with an Apple charger?

The issue was confirmed with two separate MagSafe chargers and three or four separate AC/DC chargers. The lab test in the post was done using laboratory DC power supply powering a DC to USB converter.

Also if the interference didn't come from the disc side of charger then the issue wouldn't be resolved with ferrite bead on that end. If the issue was on the USB connector side then the bead should be placed there.

The author holds a Finnish call sign, so it would be more appropriate the Finnish authorities (Traficom). That said, it's still a bad look on Apple's design or production engineering. I would expect a higher level of quality.

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.

My problem with literally every wireless charger I ever used is awful coil whine or ticking noise, really disturbing if you have the charger next to your bed. I've tried official Apple one, Samsung one, Anker, Auckley, few other random chinese brands, and they are all so loud when charging(Samsung's is probably the worst for it, as it has a fan inside - yes it charges my S23 pretty quickly but I wouldn't use it anywhere other than a loud office environment). I don't know if this is a problem of insulation or is it just inevitable given the technology used.

Interesting...I've used my Apple MagSafe charger since its release with the iPhone 12 and I have never once noticed a whine or ticking from it. AFAIK, I do not have exceptional hearing loss from age and I am able to hear all but the highest of frequencies in the audible spectrum. Would you call it particularly high pitched?

Yeah.....like a very high pitched whine. At low battery level it's pretty much steady, then as it gets close to 100% the charger clearly provides power in pulses as it goes on and off with longer and longer gaps.

I’m very sensitive to coil whine (and have documented hyperacusis for high-pitched noises) but I’ve had no issues with the Belkin wireless fast charger; BUT if you’ve had this issue with all the different makes and models perhaps it is the coil in the phone and not the one in the charger that is faulty? There’s a coil in each.

There was an audible digital clock noise (of the phone) "ground loop" when charging an iPhone 6S on the same ground potential as wireless headphones Bose QC 35 (v1) while also charging the headphones AND connected via the analog headphone jack to the phone. (The noise was very loud in the headphones while operating in a passive analog input (powered off) while charging.)

Moving either charger to a different ground potential removed the issue. There was probably a missing backfeed filter diode on a ground track or decoupling capacitor somewhere in the headphones' charging circuit.

Apple have form for some very odd stray vibrations around their macbook and being on charge. It's a not-electric-but-you-think-it-is thing around soft-touching their brushed aluminium case, sometimes.

The "gosh, this is hot" thing when its on charge has been an issue from time to time, as the magsafe ages out, or some component on the mac board. Apparently its caused by HF on top of the desired DC, leaking out the componentry somehow as mechanical vibration.

It is electric, and it happens when you're on ungrounded AC.

The write ups I've read said it was a microvibration on the board, not leakage into you. Its origin is electric no matter what.

It’s leakage current. Again, it only happens when ungrounded.

And happens also on multiple DELL laptops I used/touched.

It's just a grounding issue, just that you feel the 50/60hz and your skin detects it as a weird texture/vibration.

I think the periodic electric impulses may be interpreted by your brain as a fake stick-slip phenomenon and change how the texture feels.

See: https://superuser.com/questions/462244/electric-shock-mild-v...

Pretty detailed and creative write-up, but my first thought was “how would it have worked with a 20000mAh battery ?” - admittedly a cludge, but could be much simpler..

How are you going to get that 20Ah battery into an iphone?

Why would one need to get it into the iPhone/iPad ? Just use a power bank. (I wonder if the PD circuitry would be making the interference in its own right, though).

https://www.amazon.de/Samsung-Powerbank-Capacity-Charging-In...

From a marketing standpoint, Apple managed to turn "The Notch" into a feature. Whether they could do the same with "The Lump" is asking a lot IMHO.

Perhaps (as the author says), the engineers could come up with something more elegant.

Hahaha, I can imagine a buttoned up exec channeling jobs brandishing "the lump" on stage at one of their events. And he is saying: This is the best "lump" we've ever made. 20% Lumpier than the previous generation, 30% lighter, with a brand new crazonium body with a ferrite core!

The other day I used one of those ultrasonic eyeglasses cleaning machines while I had my AirPods Pro in and they went crazy with static as long as I had the machine on.

That could also be because of the noise cancelling, where the microphones are "hearing" the ultrasonic frequencies and the headphones are trying to cancel them out.

This is most likely exactly the problem. It's very unlikely that an ultrasonic cleaner operating at a few kHz will cause interference on Bluetooth.

Also interference on a digital Bluetooth signal would likely not cause incorrect sound to be played, rather just a pause, stutter, or connection loss.

And even if it did - Bluetooth is digital. At worst the music would just stop playing, and at best it would skip - there would be no static.

> The final product showing the ferrite bead with three wraps of the interference causing USB cable around it.

Isn’t that just two wraps? Or two and a half at best?

Good question/nice catch! It does look like two wraps to me as well, but fortunately the datasheet does seem to show the same impedance for that resonant frequency at either N=2 or N=3 wraps so I think it shouldn’t matter. (And despite OP’s disqualifier, I would trust the datasheet to more or less represent what’s going to happen.)

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

Form over function.

That doesn't read as correct in this case, as a bulky and heavy "bead" on the cable makes the product less functional for the purposes of most customers.

The author has different priorities but they're idiosyncratic.

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).

There's a big difference between causing interference in a receiver a few inches away versus an airplane 1000ft above you.

It may be that this charger passes the legal requirements while still causing small amounts of interference when placed near a receiver.

There’s also a big difference between one charger emitting some noise, and a couple million in a big city raising the noise floor for the frequency.

It's not Apple's job to determine if there's a problem with that and regulations on this issue are, so far as I'm aware, treated very seriously.

Sorry - I can clarify a little. If it complies with regulations, Apple is definitely not at fault.

I was just replying to the above comment which could read “a little noise from a single device isn’t a big deal.”

It is definitely up to regulators to decide what is acceptable, and up to Apple to meet those regulations. It’s still a little unclear from the OP whether or not the spurious emissions meet transmission requirements, but it definitely a good place to do further lab tests for compliance.

Maybe! Seems a little unlikely that Apple could fly something like that under the radar, not for very long, but mistakes happen.

Do bodies like the FCC independently verify compliance?

We're talking "little" as in "need a powerful microscope to see it", not "small".

Inverse square law dude. We're talking about nanowatts, at most, here.

> 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.

> Part of the FCC certification process is that devices need to accept interference from other devices operating within the limits

Note that only some classes of device have this requirement to accept all interference from devices operating within the limits. For some classes of devices if a consumer device interferes with then the consumer device's owner is responsible for stopping the interference even if the consumer device is operating entirely within limits.

The FCC regulations are divided into several parts, covering different devices and services. For example Part 87 covers various aviation radio services and devices, Part 97 covers Amateur Radio, and Part 20 covers mobile phones.

For any given frequency there might be devices or services covered under several different parts that can radiate on that frequency. There will generally be some kind of hierarchy among them where devices are not allowed to interfere with devices higher in the hierarchy and must accept interference from devices higher in the hierarchy.

The Part that covers much of consumer electronics other than mobile phones is Part 15. For most common consumer devices, if it is not a mobile phone and you did not need to get a license from the FCC to use it it probably falls under Part 15. This includes "intentional radiators", which are devices that are intended to emit radio such as WiFi routers, "unintentional radiators", which are devices that intentionally generate radio frequency energy within the device but it is meant to stay within wires or within the device, and "incidental radiators", which are devices that aren't intended to generate radio frequency energy but do so as a side effect such as DC motors and mechanical light switches.

Part 15 is at the bottom of the hierarchy.

For Part 15 devices, 47 CFR 15.5(b) says:

> Operation of an intentional, unintentional, or incidental radiator is subject to the conditions that no harmful interference is caused and that interference must be accepted that may be caused by the operation of an authorized radio station, by another intentional or unintentional radiator, by industrial, scientific and medical (ISM) equipment, or by an incidental radiator.

Other Parts can have quite different rules. For example Part 95 Subpart C, which covers radio control such as is commonly used in RC models, says this:

> (a) RCRS stations must not cause interference to:

> (1) Authorized radio operations in the 72–76 MHz band, including radio remote control of industrial equipment on the same or adjacent channels; or,

> (2) Broadcast television reception on TV Channels 4 or 5.

> (b) RCRS operations are not afforded protection from interference caused by the operation of:

> (1) Industrial, scientific or medical devices (see part 18 of this chapter) operating in the 26–28 MHz band; and,

> (2) Fixed and mobile stations in other services operating on the same or adjacent channels.

For Amateur ("ham") Radio, the interference rules are much more extensive, because hams are authorized to use a lot of frequency bands that overlap other services. Here's a link if anyone is curious [1].

[1] https://www.law.cornell.edu/cfr/text/47/97.303

The author's minimal effort was facilitated by his access to specialized equipment and time researching the issue.

And as others have mentioned, Apple could have placed a small ferrite on the power supply PCB to achieve the same effect.

> The author's minimal effort

The minimal effort included hours of studying electrical engineering and radio technology at university including all the math and physics needed. Studying for amateur radio license. And after founding this issue delving deep into radio interference literature and datasheets of various components. Then setting up a test environment to replicate the issue and do tests trying to eliminate the interference. After a success write a blog post describing the solution in short and hopefully interesting way.

It coincides with several frequencies used by air traffic control in my country. I don't think it would be noticeable, but it still rises the noise floor. It's not that hard to wave a piece of nicked coax over such gadget and I expect Apple to have a 200 MHz scope to connect the coax to and see if there are any peaks in the problematic bands that might need filtering.

Just contrary, cheap products / poor engineering team use them on devices such as low end laptop chargers, usually on the DC power cord to pass EMC compliance tests. A good designed product fix them in the electronic circuits.

An underrated observation. For example, the worst USB cables in my experience aren't the ones with no ferrites, they're the ones with the ferrites.

They don't have to be on the outside, they can be inside the PSU.

And in that case they would be smaller and cheaper.

It passed EMC so the ferrite is not needed and omitting it is literally a million dollars decision. And no surprise, the spectrum images he posted look fine. It's not and never was about eliminating all emissions, and his problem is purely putting the thing right next to the receiver.

The "bulky ferrite" he used is an easy 'hack.' the correct way to fix this wouldn't be as expensive or as bulky, as noted in the article: "I expect Apple could solve this problem with much cheaper and hidden it somewhere cleverly."

I'm not so sure. I can't think os a solution other than a choke off the top of my head.

You see these in circuits incorporating SMPS all the time: https://www.digikey.com/en/product-highlight/f/fair-rite-pro...

Smaller, cheaper, lighter, better. Just hard to retrofit if they weren’t designed as part of the board to begin with.

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.

Did the ferrite on the power cord , reduce the charge efficiency ?

so does this make charging more efficient? does it help preserve hardware in the long-run?

is there a guarantee that these frequencies weren't added in for some engineered purpose?

I have a feeling this makes charging less... not efficient, but slower charging.

The end of this thing is a bunch of wire in a loop, the inductor that transfers the energy to the phone. So it was odd to me that he chose the cord as the antenna that was broadcasting the noise, when I'd think it would be the business end. These frequencies being broadcast might be overlooked harmonics, ok to filter out, but they might be a designed part of the energy transfer that the charger is attempting. It's possible that he's damped the noise and the charging, but under normal use he doesn't need the maximum charge so it's still a win.

not my specialty, just speculating based on basic EE knowledge.

It’s not hard to verify before throwing shade at OP’s work. 1) article specifically mentions the actual frequencies used by wireless charging up top, 2) you can refer to Wikipedia to see the same [0]: the frequency for charging is the much lower From 87-205 KILOhertz (while the harmful frequencies being filtered out are in the hundreds of MEGAhertz).

So, no, this doesn’t slow down charging.

[0]: https://en.wikipedia.org/wiki/Inductive_charging

Seems like an FCC complaint is in order

>But it really bothers me to buy 40€ product and I still need to fix it with component costing over 2€

Honestly doesn't surprise me. I hold the same kind of sentiment after spending $1200~ on a brand new iphone 14 pro max just to find that I had to buy the charger brick so I could plug it into a wall. Come on Apple. Eliminating QOL things doesn't just automatically equal improvement.

Probably like 98% of customers already have a USB power source of some kind, so that seems like a reasonable cut corner.

Not really, modern phones have fast charge capability that's been improving generation over generetion, so what happens is new chargers are bought to take advantage of that. The older gen chargers are E-waste either way, and apple gets to charge us for something they should have included.

Not that I endorse cutting more corners, but I personally gave away the 30w dual USBC charger that came with my MacBook Air since I already own plenty of higher powered ones that work with other devices like my work MBP and Nintendo Switch etc.

I think it'd be great if Apple offered a small discount for opting out of unnecessary items.

I don't know the percentage of course, but I think you'll agree that at least part of the client base will simply reuse their existing charger.

Older gen chargers didn't just become e-waste suddenly because newer bricks that support faster charging are available. I've still got a couple of the 5W USB-A bricks sitting around that I like for slow-charging devices.

USB Power Delivery has been pretty stable; even my oldest charger, bought in 2017, is capable of fast charging the latest iPhone and Android devices – except for those exclusively using some proprietary "fast charge" crap (which is strongly discouraged by the USB-C specification).

iPhone fast charging hasn't really changed over the years, it's still only 25W max, which can be satisfied even by early USB PD chargers.

Androids have their fancy ~100W fast charging where all of the charge controlling is in the brick for thermal reasons and those require special proprietary chargers that become obsolete after a generation, but Apple doesn't do that.

That doesn’t mean they have chargers that meet the wattage and port needs of newer phones. I still use an iPhone XS Max, which uses a 5 watt usb a charger. If I upgrade to an iPhone 15 I will need to get an usb a to c cable and the phone will take forever to charge. I don’t even know if that wattage is enough to charge the phone while it’s on, especially with the pro models.

Or they could just include a 20 watt usb c charger with my $800-1200+tax and activation fees phone and not force me to spend another $60 on their power adapter. though to be fair a third party option would certainly be less expensive.

It’s amusing that you’re getting downvoted when that was the entire point of forcing Apple to standardize on USB-C like the rest of the electronics industry.

That's not analogous. Not including the charger in newer iPhones actually reduced e-waste for me personally. I have collected many charges over the years and don't need more. When a device fails or I trade it in - I keep the charger (as most people I would think).

Perhaps they should have made the charger optional... but completely agree overall with the decision not to include it.

I would agree that its fine to not include it, had they not switched to usb-c right when they stopped including bricks so all my new devices came with usb-c chargers but I only have usb-a bricks

iPhones stopped shipping with power bricks with the iPhone 12 back in 2020, so it's not exactly new that they're not including the charging brick.

https://www.theverge.com/2020/10/13/21514480/apple-iphone-ch...

To be fair, they did include a USB-C charger with the iPhone 11 for one year. But yeah, people on a two-year upgrade (or longer) cadence will likely not have had an Apple USB-C power adapter included with any of their devices.

Only the Pro models, the base model still came with a 5W A brick

I don't want a cheap charging brick with my $1,200 phone. And I don't want to pay more for a nice brick to be included either because I already have one. Good bricks outlive phones. No brick is much better. Buy whatever brick you need whenever you need it.

The only argument is "well, then they should have dropped the price of the phone." Okay dropped it relative to what? "Obviously relative to last year's price." Why? There is/was heavy inflation and other products became more expensive but the iPhone didn't. At most you are complaining about shrinkflation.

I have a box full of various Apple chargers. Anybody who wants one can have one.

I’m pleased Apple stopped adding enormous amounts of ewaste by not producing tens or hundreds of millions of these things every year for the majority of people who do not need them.

Reply on news.ycombinator.com