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Hackaday Links: November 20, 2022

Lots of space news this week, with the big story being that Artemis I finally blasted off for its trip to the Moon. It was a spectacular night launch, with the SLS sending the crew-rated but vacant — well, mostly vacant — Orion spacecraft on a week-ish long trip to the Moon, before spending a couple of weeks testing out a distant retrograde orbit. The mission is already returning some stunning images, and the main mission goal is to check out the Orion spacecraft and everything needed for a crewed Artemis II lunar flyby sometime in 2024. If that goes well, Artemis III will head up in 2025 with a crew of four to put the first bootprints on the Moon in over 50 years.

Of course, like the Apollo missions before it, a big part of the crewed landings of the Artemis program will likely be the collection and return of more lunar rock and soil samples. But NASA likes to hedge its bets, which is perhaps why they’ve announced an agreement to purchase lunar regolith samples from the first private company to send a lander to the Moon. The Japanese start-up behind this effort is called ispace, and they’ve been issued a license by the Japanese government to transfer samples collected by its HAKUTO-R lander to NASA. Or rather, samples collected on the lander — the contract is for NASA to take possession of whatever regolith accumulates on the HAKUTO-R’s landing pads. And it’s not like ispace is going to return the samples — the lander isn’t designed to ever leave the lunar surface. The whole thing is symbolic of the future of space commerce, which is probably why NASA is only paying $5,000 for the dirt.

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This Standalone Camera Gets The Picture Through With SSTV

These days, sending a picture to someone else is as simple as pulling out your smartphone and sending it by email or text message. It’s so simple a child can do it, but that simple user experience masks a huge amount of complexity, from the compression algorithms in the phones to the huge amount of distributed infrastructure needed to connect them together. As wonderful and enabling as all that infrastructure can be, sometimes it’s just too much for the job.

That seems to have been the case for [Dzl TheEvilGenius], who just wanted to send a low-resolution image from a remote location. It turns out that hams solved that problem about 70 years ago with slow-scan television, or SSTV. While most of the world was settling down in front of “I Love Lucy” on the regular tube, amateur radio operators were figuring out how to use their equipment to send pictures around the world. But where hams of yore had to throw a considerable amount of gear at the problem, [Dzl] just used an ESP-32 with a camera and some custom code to process the image. The output from one of the MCU’s GPIO pins is a PWM audio signal which can be fed directly into the microphone input of a cheap portable transceiver.

To decode the signal, [Dzl] used one of the many SSTV programs available. There’s no mention of the receiver, although it could be pretty much anything from another Baofeng to an SDR dongle. The code is available in the article, as is an audio file of an encoded image, if you just want to play around with the receiving and decoding side of the equation.

We could see something like this working for a remote security camera, or even for scouting hunting spots. If you want to replicate this, remember that you’ll need a license if you want to transmit on the ham bands — relax, it’s easy.

Listen To 64 MHz At Once

We imagine that if [Tech Minds] told us he was listening to the HF bands, we might ask him which one? His reply might just be “All of them.” That’s thanks to the RX-888 MKII SDR he reviewed which delivers a 64 MHz window on the radio spectrum. You can catch the video review, below.

These are not especially inexpensive, but with that bandwidth and 16-bit resolution, it is worth it if you need that kind of horsepower. There is a separate input for VHF signals 64-1700 MHz where the bandwidth is only 10 MHz, but still.

Of course, making a very wideband front end for something like this is non-trivial, so we wonder how the performance is compared to similar-priced units with less bandwidth. On the other hand, it does seem to work well enough in the video. The software used limited the test to a 32 MHz bandwidth, which is still plenty.

Speaking of software, we noticed that the developers of SatDump and SDR++ are not happy with the state of the software for the RX-888. We aren’t sure if this remains a problem, but the device seemed to work well on the video, at least.

There are many options now when it comes to higher-end SDRs. We like the Pluto for both transmitting and receiving. Of course, the RTL-SDR kind of started everything with hobby SDR, but you can’t expect that much bandwidth with one of those.

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Getting To The Heart Of A Baofeng

In amateur radio circles, almost no single piece of equipment serves as more of a magnet for controversy than the humble Baofeng handheld transceiver. It’s understandable — the radio is a shining example of value engineering, with just enough parts to its job while staying just on the edge of FCC rules. And at about $25 a pop, the radios are cheap enough that experimentation is practically a requirement of ownership.

But stripped down as the Baofeng may be, it holds secrets inside that are even more tempting to play with than the radio itself. And who better than [HB9BLA], a guy who has a suspiciously familiar Swiss accent, to guide us through the RF module at the heart of the Baofeng, the SA818. For about $8 you can get one of these little marvels off AliExpress and have nearly all the important parts of a VHF or UHF radio — an SDR transceiver, a power amp, and all the glue logic to make it work.

In the video below, [Andreas] puts the SA818 module through its paces with the help of a board that pairs the module with a few accessories, like an audio amp and a low-pass RF filter. With a Raspberry Pi and a Python library to control the module, it’s a decent imitation of the functionality of a Baofeng. But that’s only the beginning. By adding a USB sound card to the Pi, the setup was able to get into every ham’s favorite packet radio system, APRS. There are a ton of other applications for the SA818 modules, some of which [Andreas] mentions at the end of the video. Pocket-sized repeaters, a ridiculously small EchoLink hotspot, and even an AllStar node in an Altoids tin.

Of course, if you want to get in on the fun, you’re going to need an amateur radio license. Don’t worry, it’s easy — we’ll help you get there.

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Direction-Finding With Help From The Steam Deck

Direction-finding, or fox hunting, is a popular activity in ham radio circles where a group of people armed with radios attempt to locate a broadcasting source. Besides being a hobby for amateurs, it’s also a necessary tool in the belt of regulators who are attempting to track down violators of the air space. There are a lot of ways to figure out the precise location of a radio transmission, but this one manages to pull it off using both a boat and a Steam Deck, each armed with a software-defined radio.

This project comes to us from [Aaron] who is well known in the amateur radio circles for his SDR-focused Linux distribution called DragonOS; which has all the tools needed for a quality SDR experience, in this case KrakenSDR and DF Aggregator. He’s loaded everything up on a Steam Deck and left that in a secure location on the shore of a lake, while he carries second device with the same software with him on a boat. With the two devices listening for a specific signal, he’s able to quickly zero in on his friend on the shore who is broadcasting on the 70 cm band thanks to the help of all of these software packages.

While ham radio isn’t always known for being a youthful and exciting activity, the advent of software-defined radio and other digital modes seem to be shaking things up in that world. Certainly speeding around a lake on a boat is fun on its own as well, and a fox hunt like this can be done with something as small and simple as a Raspberry Pi too.

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TRX-Duo Is A Red Pitaya Clone For Software Defined Radio

If you’ve noticed the TRX-DUO software-defined radio transceiver, you might have wondered how it stacks up to other choices like Red Pitaya or HackRF.  [Tech Minds] obliges with a review of the Red device in the video below.

While this unit isn’t inexpensive, it also isn’t as expensive as some of its competitors. Sure, you can pick up an RTL-SDR dongle for a fraction of the price, but then you miss out on transmitting. The device is pretty powerful compared to a cheap software defined radio:

  • Frequency: 10 kHz to 60 MHz
  • CPU: Zynq SoC with a dual-core ARM Cortex A9
  • RAM: 512 MB
  • OS: Linux
  • Connectivity: Ethernet and USB connectivity (WiFi with a dongle)
  • ADC: 16-bit at 125 MS/s (2 channels)
  • DAC: 14-bit at 125 MS/s (2 channels)

The board boots off an SD card and there are several to choose from. The video shows two different images. One has a number of applications that run on the device and will also run on a Red Pitaya. The device shows a browser menu with various options and the result is quite impressive. Using the box as a WSPR beacon, it was heard fairly well given the low output power. It was, however, able to hear the world easily.

You can get a less capable Red Pitaya model for about $100 less than the going price. However, for something comparable, you will pay more for the Red Pitaya and — depending on capabilities — perhaps a lot more, although you do get more capability for the increased price.

You can do a lot more with a transmitting SDR — having both transmit and receive opens up many new projects. Of course, canned applications are great, but if you get one of these, you are going to want to try GNU Radio.

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London Bridge Has Fallen — By Radio

One of the global news stories this week has been the passing of the British monarch, Queen Elizabeth II. Since she had recently celebrated 70 years on the throne, the changing of a monarch is not something that the majority of those alive in 2022 will have seen. But it’s well known that there are a whole suite of “London Bridge has fallen” protocols in place for that eventuality which the various arms of the British government would have put in motion immediately upon news from Balmoral Castle. When it became obvious that the Queen’s health was declining, [Hackerfantastic] took to the airwaves to spot any radio signature of these plans. [Update 2022-09-11] See the comments below and a fresh Tweet to clarify, it appears these were not the signals they were at first suspected to be.

What he found in a waterfall view of the 4 MHz military band was an unusual transmission, a set of strong QPSK packets that started around 13:40pm on the 8th of September, and continued on for 12 hours before disappearing.  The interesting thing about these transmissions is not that they were a special system for announcing the death of a monarch, but that they present a rare chance to see one of the country’s Cold War era military alert systems in action.

It’s likely that overseas embassies and naval ships would have been the intended recipients and the contents would have been official orders to enact those protocols, though we’d be curious to know whether 2022-era Internet and broadcast media had tipped them off beforehand that something was about to happen. It serves as a reminder: next time world news stories happen in your part of the world, look at the airwaves!