Hackaday Links: December 20, 2020

If development platforms were people, Google would be one of the most prolific serial killers in history. Android Things, Google’s attempt at an OS for IoT devices, will officially start shutting down on January 5, 2021, and the plug will be pulled for good a year later. Android Things, which was basically a stripped-down version of the popular phone operating system, had promise, especially considering that Google was pitching it as a secure alternative in the IoT space, where security is often an afterthought. We haven’t exactly seen a lot of projects using Android Things, so the loss is probably not huge, but the list of projects snuffed by Google and the number of developers and users left high and dry by these changes continues to grow. Continue reading “Hackaday Links: December 20, 2020”

Hackaday Links: February 23, 2020

If you think your data rates suck, take pity on New Horizons. The space probe, which gave us lovely pictures of the hapless one-time planet Pluto after its 2015 flyby, continued to plunge and explore other, smaller objects in the Kuiper belt. In January of 2019, New Horizons zipped by Kuiper belt object Arrokoth and buffered its findings on the spacecraft’s solid-state data recorders. The probe has been dribbling data back to Earth ever since at the rate of 1 to 2 kilobits per second, and now we have enough of that data to piece together a story of how planets may have formed in the early solar system. The planetary science is fascinating, but for our money, getting a probe to narrowly miss a 35-kilometer long object at a range of 6.5 billion km all while traveling at 51,500 km/h is pretty impressive. And if as expected it takes until September to retrieve all the data from the event at a speed worse than dialup rates, it’ll be worth the wait.

Speaking of space, if you’re at all interested in big data, you might want to consider putting your skills to work in the search for extraterrestrial intelligence. The Berkeley SETI Research Center has been feeding data from the Green Bank Telescope and their Automated Planet Finder into the public archive of Breakthrough Listen, a 10-year, $100 million initiative to scan the million closest stars in our galaxy as well as the 100 nearest galaxies for signs of intelligent life. They’re asking for help to analyze the torrents of data they’re accumulating, specifically by developing software and algorithms to process the data. They’ve set up a site to walk you through the basics and get you started. If you’re handy with Python and have an interest in astronomy, you should check it out.

Staying with the space theme, what’s the best way to get kids interested in space and electronics? Why, by launching a satellite designed to meme its way across the heavens, of course. The Mission for Education and Multimedia Engagement satellite, or MEMESat-1, is being planned for a February 2021 launch. The 1U cubesat will serve as an amateur radio repeater and slow-scan TV (SSTV) beacon that will beam down memes donated to the project and stored on radiation-hardened flash storage. In all seriousness, this seems like a great way to engage the generation that elevated the meme to a modern art form in a STEM project they might otherwise show little interest in.

It looks as though Linux might be getting a big boost as the government of South Korea announced that they’re switching 3.3 million PCs from Windows to Linux. It’s tempting to blame Microsoft’s recent dropping of Windows 7 support for the defenestration, but this sounds like a plan that’s been in the works for a while. No official word on which distro will be selected for the 780 billion won ($655 million) effort, which is said to be driven by ballooning software license costs and a desire to get out from under Microsoft’s thumb.

And finally, in perhaps the ickiest auction ever held, the “Davos Collection” headed to the auction block this week in New York. The items offered were all collected from the 2018 World Economic Forum in Davos, Switzerland, where the world’s elites gather to determine the fate of the 99.999%. Every item in the collection, ranging from utensils and glassware used at the many lavish meals to “sanitary items” disposed of by the billionaires, and even hair and fluid samples swabbed from restrooms, potentially holds a genetic treasure trove in the form of the DNA it takes to be in the elite. Or at least that’s the theory. There’s a whole “Boys from Brazil” vibe here that we find disquieting, and we flatly refuse to see how an auction where a used paper cup is offered for $8,000 went, but if you’d like to virtually browse through the ostensibly valuable trash of oligarchs, check out the auction catalog.

Space Technology And Audio Tape To Store Art

[Blaine Murphy] has set out to store an archive of visual art on cassette tape. To do so he encodes images via Slow-Scan Television (SSTV), an analogue technology from the late 50s which encodes images in for radio transmission. If you are thinking ‘space race’ you are spot on, the first images of the far side of the moon reached us via SSTV and were transmitted by the soviet Luna 3 spacecraft.

Yes, this happened

Encoding images with 5os technology is only one part of this ongoing project. Storage and playback are handled by a 90s tape deck and the display unit is a contemporary Android phone. Combining several generations in one build comes with its own set of challenges, such as getting a working audio connection between the phone and the tape deck or repairing old consumer electronics. His project logs on this topic are solid contenders for ‘Fail Of The Week’ posts. For instance, making his own belts for the cassette deck was fascinating but a dead end.

The technological breadth of the project makes it more interesting with every turn. Set some time aside this weekend for an entertaining read.

Just a couple of years back ham radio operators had the opportunity to decode SSTV beamed down from the ISS when they commemorated [Yuri Gagarin’s] birthday. Now if the mechanical part of this project is what caught your interest, you’ll also want to look back on this MIDI sampler which used multiple cassette players.

How To Receive Pictures From Spaaace!

The International Space Station, or ISS, has been in orbit in its various forms now for almost twenty years. During that time many of us will have stood outside on a clear night and seen it pass overhead, as the largest man-made object in space it is clearly visible without a telescope.

Most ISS-watchers will know that the station carries a number of amateur radio payloads. There are voice contacts when for example astronauts talk to schools, there are digital modes, and sometimes as is happening at the moment for passes within range of Moscow (on Feb. 14, 11:25-16:30 UTC) the station transmits slow scan television, or SSTV.

You might think that receiving SSTV would be hard work and require expensive equipment, but given the advent of ubiquitous mobile and tablet computing alongside dirt-cheap RTL-SDRs it is now surprisingly accessible. An Android phone can run the SDRTouch software defined radio app as well as the Robot36 SSTV decoder, and given a suitable antenna the pictures can be received and decoded relatively easily. The radio must receive 145.8MHz wideband FM and the decoder must be set to the PD120 PD180 mode (Thanks [M5AKA] for the update), and here at least the apps are run on separate Android devices. It is possible to receive the signal using extremely basic antennas, but for best results something with a little gain should be used. The antenna of choice here is a handheld [HB9CV] 2-element beam.

A failed grab from a 2014 transmission, proving that Hackaday scribes don't always get perfect results.
A failed grab from a 2015 transmission, proving that Hackaday scribes don’t always get perfect results.

You can find when the station is due to pass over you from any of a number of ISS tracker sites, and you can keep up to date with ISS SSTV activity on the ARISS news page. Then all you have to do is stand out in the open with your receiver and computing devices running and ready, and point your antenna at the position of the station as it passes over. If you are lucky you’ll hear the tones of the SSTV transmission and a picture will be decoded, if not you may receive a garbled mess. Fortunately grabs of other people’s received pictures are posted online, so you can take a look at what you missed if you don’t quite succeed.

Even if you don’t live within range of a pass, it’s always worth seeing if a Web SDR somewhere is in range. For example this Russian one for the current transmissions.

In that you are using off-the-shelf hardware and software you might complain there is little in the way of an elite hack about pulling in a picture from the ISS. But wait a minute — you just received a picture from an orbiting space station. Do that in front of a kid, and see their interest in technology come alive!

RPiTX Turns Rasberry Pi Into Versatile Radio Transmitter

Since the discovery that some USB TV tuner dongles could be used to monitor radio waves across a huge amount of spectrum, the software-defined radio world has exploded with interest. The one limiting factor, though, has been that the dongles can only receive signals; they can’t transmit them. [Evariste Okcestbon, F5OEO] (if that is his real name! Ok c’est bon = Ok this is good) has written some software that will get you transmitting using SDR with only a Raspberry Pi and a wire.

There have been projects in the past that use a Pi to broadcast radio (PiFM), but this new software (RPiTX) takes it a couple steps further. Using just an appropriately-sized wire connected to one of the GPIO pins, the Raspberry Pi is capable of broadcasting using FM, AM, SSB, SSTV, or FSQ signals. This greatly increases the potential of this simple computer-turned-transmitter and anyone should be able to get a lot of use out of it. In the video demo below the break, [Evariste] records a wireless doorbell signal and then re-transmits it using just the Rasbperry Pi.

The RPiTX code is available on GitHub if you want to try it out. And it should go without saying that you will most likely need an amateur radio license of some sort to use most of these features, depending on your locale. If you don’t have a ham radio license yet, you don’t need one to listen if you want to get started in the world of SDR. But a ham license isn’t hard to get and at this point it shouldn’t take much convincing for you to get transmitting.

Continue reading “RPiTX Turns Rasberry Pi Into Versatile Radio Transmitter”

TV Broadcasts From Outer Space

According to ARISS (Amateur Radio on the International Space Station), the ISS will be sending us images using slow-scan TV on April 11th in honor of Russian cosmonaut Yuri Gagarin’s birthday. Tune in and you’ll get to see 12 different commemorative images from space, and of course bragging rights that you directly received them with your radio setup.

For those who aren’t Ham radio types, slow-scan TV (SSTV) is a radio mode where the pixels in an image are sent by encoding the brightness and/or color as a tone, a lot like a modem, fax machine, or the data cassette tapes of yore.

The ISS uses PD-180 which is a color mode where each pixel’s red, green, and blue values are encoded in a pitch between 1500 and 2300 Hz. Each image takes just over three minutes to transmit, meaning you’ll have to track the ISS pretty well as it travels across the sky. But don’t fret, they send each message for around an hour, so you have a good chance to receive it. (We’ll be the first to admit that a frame rate of one frame in 187 seconds isn’t really “TV”, but that’s what they call it.)

SSTV’s use in the space program goes back even before the moon landing, but with modern software-defined radio setups, it all becomes a lot more convenient to receive. The ISS folks do this periodically as a service to the amateur radio community, so it’s a good time to try out your chops.

We’ve covered ARISS before, but Yuri’s birthday is always a good reason to celebrate the folks out there. And if you need a reminder of when to look up, this hack right here has you covered.

If you do receive some images, you can upload them to the ARISS Gallery.  Or you can just hit refresh to see them as others post them up.

SSTV Beacon Based On A Raspberry Pi

The Budapest hackerspace did some joint work with a local ham radio club and created an SSTV beacon housed inside a CCTV case that takes an image of its environment and transmits it using slow-scan television over ham bands.

As the title says, the build uses a Raspberry Pi to process the image taken from its camera and then transmits it over the air using a Ricofunk UHF transceiver with a main frequency of 433.425MHz. On the software side, PySSTV is used to convert images to frequency/time tuples, UNIXSSTV then creates the actual audio file and finally sox plays it. To avoid screwing up the Raspberry SD card, every part of the filsystem is either mounted in read-only mode (things like /home and /usr) or uses a ramdisk (things like /tmp and logs).

The plans, schematics and source code are available, so they hope that other hackerspaces will join the ranks!