[HN Gopher] Eliminating radio interference from Apple charger
___________________________________________________________________
Eliminating radio interference from Apple charger
Author : oherrala
Score : 143 points
Date : 2023-10-04 18:01 UTC (4 hours ago)
(HTM) web link (oh8hub.substack.com)
(TXT) w3m dump (oh8hub.substack.com)
| NegativeLatency wrote:
| I wonder if someone suggested this at apple and was overruled
| because a bulky ferrite would "look bad"
| yftsui wrote:
| 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.
| CamperBob2 wrote:
| 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.
| teaearlgraycold wrote:
| Form over function.
| Clamchop wrote:
| 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.
| stefan_ wrote:
| 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.
| dangus wrote:
| 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.
| mordae wrote:
| 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.
| oherrala wrote:
| 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).
| stetrain wrote:
| 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.
| pnpnp wrote:
| 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.
| Clamchop wrote:
| 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.
| pnpnp wrote:
| 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.
| Clamchop wrote:
| 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?
| terr-dav wrote:
| 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.
| wkat4242 wrote:
| They don't have to be on the outside, they can be inside the
| PSU.
| sigmar wrote:
| 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."
| oldbbsnickname wrote:
| 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.
| Animats wrote:
| > 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...
| numpad0 wrote:
| 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!?
| SV_BubbleTime wrote:
| >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.
| mtreis86 wrote:
| 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.
| SV_BubbleTime wrote:
| 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
| genewitch wrote:
| 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!
| [deleted]
| Animats wrote:
| 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...
| SV_BubbleTime wrote:
| 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.
| wkat4242 wrote:
| 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.
| colechristensen wrote:
| 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.
| amatecha wrote:
| 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.
| js2 wrote:
| 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.)
| [deleted]
| NovemberWhiskey wrote:
| > _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.
| PM_me_your_math wrote:
| [dead]
| crote wrote:
| 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?
| amatecha wrote:
| 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
| NovemberWhiskey wrote:
| 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.
| amatecha wrote:
| 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.
| NovemberWhiskey wrote:
| 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.
| amatecha wrote:
| 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.
| jrockway wrote:
| 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.
| amatecha wrote:
| 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/
| jrockway wrote:
| 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.)
| NovemberWhiskey wrote:
| 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.
| amatecha wrote:
| 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).
| jrockway wrote:
| 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!
| t0mas88 wrote:
| 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.
| jrockway wrote:
| > 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.)
| NtG_UK wrote:
| 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.
| ay wrote:
| 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..
| threemux wrote:
| 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.
| chankstein38 wrote:
| >But it really bothers me to buy 40EUR product and I still need
| to fix it with component costing over 2EUR
|
| 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.
| colechristensen wrote:
| 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.
| twiceaday wrote:
| 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.
| wyager wrote:
| Probably like 98% of customers already have a USB power source
| of some kind, so that seems like a reasonable cut corner.
| hellotheretoday wrote:
| 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.
| tails4e wrote:
| 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.
| artimaeis wrote:
| 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.
| lxgr wrote:
| 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).
| ProfessorLayton wrote:
| 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.
| bartvk wrote:
| 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.
| Bud wrote:
| [dead]
| ZekeSulastin wrote:
| 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.
| 90-00-09 wrote:
| 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.
| bdav2418 wrote:
| 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
| artimaeis wrote:
| 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...
| lxgr wrote:
| 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.
| sdflhasjd wrote:
| 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.
| mschuster91 wrote:
| 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.)
| sdflhasjd wrote:
| 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*.
| MilaM wrote:
| 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?
| unsupp0rted wrote:
| 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.
| stetrain wrote:
| 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.
| wkat4242 wrote:
| 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.
| stetrain wrote:
| Also interference on a digital Bluetooth signal would
| likely not cause incorrect sound to be played, rather just
| a pause, stutter, or connection loss.
| somehnguy wrote:
| 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.
| exabrial wrote:
| Seems like an FCC complaint is in order
| hulitu wrote:
| > Eliminating Radio Interference from Apple Charger
|
| Why not notify the FCC ?
| yftsui wrote:
| 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.
| oherrala wrote:
| The device was ordered from Apple's website.
| yftsui wrote:
| The issue could be coming from the AC-DC charger used with
| the MagSafe charger as well, maybe retest with an Apple
| charger?
| oherrala wrote:
| 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.
| pc486 wrote:
| 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.
| JoeAltmaier wrote:
| 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?
| gorkish wrote:
| 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.
| genewitch wrote:
| where can one buy a bag of ferrites?
| urlgrey wrote:
| There are several options from Amazon, try searching for
| "Clip-on Ferrite Ring".
| klinquist wrote:
| 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.
| buildbot wrote:
| 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!
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