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Hackaday Links: June 26, 2022

June 26, 2022 by 13 Comments

Head for the hills!! We’re all doomed! At least that’s the impression you might get from the headlines about the monster Earth-facing sunspot this week. While any sunspot that doubles in size within a matter of days as AR3038 has done is worth looking at, chances are pretty low that it will cause problems here on Earth. About the best this class of sunspot can manage is an M-class solar flare, which generally cause radio blackouts only at the poles, and may present a radiation problem for the crew of the ISS. So no, this sunspot is probably not going to kill us all. But then again, this is the 2020s, and pretty much everything bad seems like it’s possible.

Speaking of bad outcomes, pity the poor Sonos customers and their ongoing battle with the company’s odd “glitches.” For whatever reason, customers have been getting shipments of Sonos products they never ordered, with at least one customer getting over $15,000 worth of products shipped. The customer reports ordering five Sonos items, but the company saw fit to fill the order six times, stuffing their apartment with goods. Sonos doesn’t appear to be doing much to make it right; while offering the customer free shipping labels to return the goods, they were expected to schlep the packages to a UPS store. And then there’s the money — Sonos charged the customer for all the unordered goods, and won’t issue a refund till it’s all returned.

If you’ve ever wondered exactly what the signals going up and down your cable line look like, you’ll want to check out this video from Double A Labs. Using an RTL-SDR dongle and some spectrum analyzer software they probed the RF signals on the cable, with some fascinating results. The first 11 minutes or so of the video are devoted to setting up the hardware and software, although there is some interesting stuff about broadband network architecture right up at the start. The scans are interesting — you can clearly see the 6-MHz quadrature amplitude modulation (QAM) digital channels. We were surprised to learn that these start at just about the FM broadcast band — about 108 MHz. There were a couple of little surprises hiding in the spectrum, like two unmodulated analog TV carriers in one spot, and the fact that there are over 400 virtual channels jammed into 41 6-MHz QAM channels. Broadband indeed.

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Broadband Across The Congo

September 20, 2021 by 34 Comments

If you live in much of the world today, high-speed Internet is a solved problem. But there are still places where getting connected presents unique challenges. Alphabet, the company that formed from Google, details their experience piping an optical network across the Congo. The project derived from an earlier program — project Loon — that used balloons to replace traditional infrastructure.

Laying cables along the twisting and turning river raises costs significantly, so a wireless approach makes sense. Connecting Brazzaville to Kinshasa using optical techniques isn’t perfect — fog, birds, and other obstructions don’t help. They still managed to pipe 700 terabytes of data in 20 days with over 99.9% reliability.

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Second-Hand Television SHINEs, Takes Down Entire Village’s Internet

September 22, 2020 by 53 Comments

We occasionally get stories on the tips line that just make us want to know more. This is especially true with tech stories covered by the mass media, which usually leave out the juicy tidbits that would just clutter up the story for the majority of non-technical readers. That leaves us to dig a little deeper for the satisfying details.

The latest one of these gems to hit the tips line is the tale of a regular broadband outage in a Welsh village. As in, really regular — at 7:00 AM every day, the internet customers of Aberhosan suffered a loss of their internet service. Customers of Openreach, the connectivity arm of the British telco BT, complained about the interruptions as customers do, and technicians responded to investigate the issue. Nobody was able to find the root cause, and despite replacing nearly all the cables in the system, the daily outages persisted for 18 months.

In the end, Openreach brought in a crack team from their Chief Engineer’s office to investigate. Working against COVID-19 restrictions, the team set up a spectrum analyzer in the early morning hours, to capture any evidence of whatever was causing the problem. At the appointed hour they saw a smear of radio frequency interference appear, a high-intensity pulse of noise at just the right frequency to interfere with the village’s asymmetric digital subscriber line (ADSL) broadband service.

A little sleuthing led to the home of a villager and a second-hand TV, which was switched on every day at 7:00 AM. The TV was found to be emitting a strong RF impulse when it was powered up, strong enough to knock out the ADSL service to the entire village. Openreach categorized this as SHINE, or single high-level impulse noise. We’d never heard of this, but apparently it’s common enough that BT warns customers about it and provides helpful instructions for locating sources with an AM radio.

We’ll say one thing for the good people of Aberhosan: they must be patient in the extreme to put up with daily internet outages for 18 months. And it’s funny how there was no apparent notice paid by the offending television’s owner that his or her steady habit caused the outage. Perhaps they don’t have a broadband connection, and so wouldn’t have noticed the borking.

In any case, the owner was reportedly “mortified” by the news and hasn’t turned the TV on since learning of the issue. This generally seems to be the reaction when someone gets caught inadvertently messing up the spectrum — remember the Great Ohio Key Fob Mystery?

Thanks to [Kieran Donnelly] for spotting this for us.

This Mostly 3D-Printed Discone Antenna Is Ready For Broadband Duty

May 29, 2018 by 16 Comments

For hams and other radio enthusiasts, the best part of the hobby is often designing antennas. Part black magic, part hard science, and part engineering, antenna design is an art. And while the expression of that art often ends up boiling down to pieces of wire cut to the correct length, some antennas have a little more going on in the aesthetics department.

Take the discone antenna, for example. Originally designed as a broadband antenna to sprout from aircraft fuselages, the discone has found a niche with public service radio listeners. But with a disk stuck to the top of a cone, the antennas have been a little hard to homebrew, at least until [ByTechLab] released this mostly 3D-printed discone. A quick look at the finished product, resembling a sweater drying rack more than a disc on top of a cone, reveals that the two shapes can be approximated by individual elements instead of solid surfaces. This is the way most practical discones are built, and [ByTechLab]’s Thingiverse page has the files needed to print the parts needed to properly orient the elements, which are just 6-mm aluminum rods. The printed hub pieces sandwich a copper plate to tie the elements together electrically while providing a feedpoint for the antenna as well as a sturdy place to mount it outdoors. This differs quite a bit from the last 3D-printed discone we featured, which used the solid geometry and was geared more for indoor use.

Interested in other antenna designs? Who can blame you? Check out the theory behind the Yagi-Uda beam antenna, or how to turn junk into a WiFi dish antenna.

[via RTL-SDR.com]

Suddenly, 4G Feels Slow

February 14, 2016 by 28 Comments

Researchers at University College London successfully transferred data over an optical transmission system at a rate of 1.125 Tb/s. That’s over ten times as fast as typical commercial optical systems, and thousands of times faster than the standard broadband connection. The study appeared in Scientific Reports and takes advantage of encoding techniques usually seen in wireless systems.

The prototype system uses fifteen channels on different wavelengths. Each channel used 256QAM encoding (the same as you see on cable modems, among other things). A single receiver recovers all of the channels together. The technology isn’t commercially available yet. It is worth noting that the experiment used a transmitter and receiver very close to each other. Future tests will examine how the system performs when there are hundreds or thousands of feet of optical fiber between them.

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Comcast Announces 250GB Bandwidth Cap

August 28, 2008 by 79 Comments


Today, Comcast updated their Acceptable Use Policy to cover exactly what they feel is “excessive use”. When the Comcast cap starts October 1st, they will contact people breaking the 250GB per month transfer limit and ask them to curb their usage. While it’ll be hard for most people to hit this limit, we still wonder if policing 0.1% of the customer base is worth the effort. At least Comcast has bothered to state the limit instead of just secretly rewriting the meaning of the word “unlimited” like some providers.

[via DSLReports]

[photo: monoglot]