Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Eliminating radio interference from Apple charger

oh8hub.substack.com

Post reply on HN
Print view View original

81–90 of 179 posts

Re: Eliminating radio interference from Apple charger

#81

Post by SV_BubbleTime »

mtreis86 wrote: post #62
SV_BubbleTime wrote: post #38

Earlier quoted context omitted.

>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

Re: Eliminating radio interference from Apple charger

#82

Post by PM_me_your_math »

NovemberWhiskey wrote: post #51
Animats wrote: post #10

> 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 po…

> 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 (…

[dead]

Re: Eliminating radio interference from Apple charger

#83

Post by amatecha »

jrockway wrote: post #79
amatecha wrote: post #71

Earlier quoted context omitted.

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

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/

Re: Eliminating radio interference from Apple charger

#84

Post by jrockway »

amatecha wrote: post #83
jrockway wrote: post #79

Earlier quoted context omitted.

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.)

Re: Eliminating radio interference from Apple charger

#85

Post by amatecha »

NovemberWhiskey wrote: post #76
amatecha wrote: post #71

Earlier quoted context omitted.

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

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

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).

Re: Eliminating radio interference from Apple charger

#86

Post by ZekeSulastin »

wyager wrote: post #22
chankstein38 wrote: post #20

>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.

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.

Re: Eliminating radio interference from Apple charger

#87

Post by mordae »

dangus wrote: post #5
NegativeLatency wrote: post #2

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

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.

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.

Re: Eliminating radio interference from Apple charger

#88

Post by Clamchop »

pnpnp wrote: post #68
Clamchop wrote: post #60

Earlier quoted context omitted.

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 requ…

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?

Re: Eliminating radio interference from Apple charger

#90

Post by klinquist »

gorkish wrote: post #45

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

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.

Post reply on HN