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...
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.
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.
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?
(I have not read the entire report and I have no expertise in RF.)
http://www.righto.com/2016/03/counterfeit-macbook-charger-te...
Very bad. Strange also because Apple usually gets their PSUs made by Delta afaik and they are as good as it gets.
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.
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.
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...
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!
Far better to use a linear power supply, which has a transformer and as a result is far heavier.
Wouldn't this then be a problem with whatever car charger he is using and not with the apple device plugged into that charger?
Fascinating. No wonders we have so much red tape on stuff that is in the air.
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.
When I'd transmit on 20m, it would sometimes open my old liftmaster garage door. Until I wrapped all of its cables in ferrites.
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.
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.
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.
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.)
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.
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*.
I don't know anything about electronics. Do you think this is some kind of defect or bad design of the power supply?
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.
It's only a problem if it's a problem. If they'd done proper filtering inside the device maybe it's ok.
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".
Why not notify the FCC ?
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.
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.
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.
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...
https://www.amazon.de/Samsung-Powerbank-Capacity-Charging-In...
Perhaps (as the author says), the engineers could come up with something more elegant.
Isn’t that just two wraps? Or two and a half at best?
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.
Seems like the author resolved the problem at minimal cost and effort.
And as others have mentioned, Apple could have placed a small ferrite on the power supply PCB to achieve the same effect.
The author has different priorities but they're idiosyncratic.
is there a guarantee that these frequencies weren't added in for some engineered purpose?
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.
So, no, this doesn’t slow down charging.
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.
Perhaps they should have made the charger optional... but completely agree overall with the decision not to include 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’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.
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.
