Radio Hacks

1329 Articles

ESPboy Turned Into Functional Walkie-Talkie

June 27, 2023 by 17 Comments

The ESPBoy was first built as a hackable open-source game engine and handheld console for educational purposes. However, it’s also a platform that can readily support all kinds of other uses. You can even turn the humble handheld device into a working walkie talkie.

The build relies on adding a SA868 transceiver module to the ESPBoy, along with a microphone, speaker, audio amplifier and antenna as supporting hardware. It then relies on the ESPBoy’s existing screen and buttons as a user interface for the radio. Assembled appropriately, it can then be used as a very basic and barebones walkie talkie for voice communication.

You won’t get coded squelch or other useful features, but it’s enough to let you talk over the air with other handheld radio users. The SA868 module can transmit on a variety of frequency bands, but the video shows it operating in the UHF band around 433 MHz. With a power on the order of 1.8W, it should get you a few kilometers of transmission range in an open field.

Check out our earlier coverage of the ESPBoy and its many different configurations. Video after the break.

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Networking With Balloons

June 26, 2023 by 14 Comments

Starlink has been making tremendous progress towards providing world-wide access to broadband Internet access, but there are a number of downsides to satellite-based internet such as the cluttering of low-Earth orbit, high expense, and moodiness of CEO. There are some alternatives if standard Internet access isn’t available, and one of the more ambitious is providing Internet access by balloon. Project Loon is perhaps the most famous of these (although now defunct), but it’s also possible to skip the middleman and build your own high-altitude balloon capable of connection speeds of 500 Kbps.

[Stephen] has been working on this project for a few months and while it doesn’t support a full Internet connection, the downlink on the high altitude balloon is fast enough to send high-resolution images in near-real-time. This is thanks to a Raspberry Pi Zero on board the balloon that is paired with an STM32 board which handles the radio communication on a RF4463 transceiver module. The STM32 acts as an intermediary or buffer to ensure reliable information is sent out on the radio, rather than using the Pi directly. [Stephen] also wrote a large chunk of the software responsible for handling all of these interactions, optimized for balloon flight specifically.

The blog post for this project was written a few weeks ago with a reported first launch date for the system already passed, so we will eagerly anticipate the results and the images he was able to gather using this system. Eventually [Stephen] hopes the downlink will be fast enough for video as well.Balloons are an underappreciated tool as well, and this isn’t the only way that they can be used to help send radio signals from place to place.

Meshtastic For The Greater Good

June 26, 2023 by 62 Comments

Last week, my city was hit by a tornado. That’s not surprising here in Oklahoma, and thankfully this event was an F0 or possibly even an EF0 — a really weak tornado. Only a couple roofs collapsed, though probably half the houses in town are going to need roof repairs, thanks to the combination of huge hail and high winds. While it wasn’t too bad, power did go down in a few places around town, and this led to an interesting series of events.

Chat messages were coming in like this: “That was a [power] flicker, yeah. Even took down my Internet.” Followed by “Whee, [fiber Internet] got knocked out and now Starlink has too many clouds in the way.” And after ten minutes of silence, we got a bit worried to see “Time to hide under a bed. … Is cell service back?” It is a bit spooky to think about trying to help neighbors and friends after a disaster, in the midst of the communication breakdown that often follows. If he had needed help, and had no working communications, how long would it have taken for us to go check on him?
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The Voice Of GPS

June 23, 2023 by 7 Comments

Tuning into a GPS satellite is nothing new. Your phone and your car probably do that multiple times a day. But [dereksgc] has been listening to GPS voice traffic. The traffic originates from COSPAS-SARSAT, which is a decades-old international cooperative of 45 nations and agencies that operates a worldwide search and rescue program. You can watch a video about it below.

Nominally, a person in trouble activates a 406 MHz beacon, and any of the 66 satellites that host COSPAS-SARSAT receivers can pick it up and relay information to the appropriate authorities. These beacons are often attached to aircraft or ships, but there are an increasing number of personal beacons used by campers, hikers, and others who might be in danger and out of reach of a cell phone. The first rescue from this system was in 1982. By 2021, 3,632 people were rescued thanks to the system.

The satellites that listen to the beacon frequencies don’t process the signals. They use a transponder that re-transmits anything it hears on a much higher downlink frequency. These transponders are always payloads on other satellites like navigation or weather satellites. But because the transponder doesn’t care what it hears, it sometimes rebroadcasts signals from things other than beacons. We were unclear if these were rogue radios or radios with spurious emissions in the translator’s input range.

The video has practical tips on how to tune in several of the satellites that carry these transponders. Might be a fun weekend project with a software-defined radio.

We’ve seen homebrew satellite devices, but none for an emergency beacon — we aren’t sure what the legal aspects of that would be. There are other satellites that unknowingly host pirate radio stations, too.

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Easy Modifications For Inexpensive Radios

June 23, 2023 by 65 Comments

Over the past decade or so, amateur radio operators have benefited from an influx of inexpensive radios based around a much simpler design than what was typically commercially available, bringing the price of handheld dual-band or GMRS radios to around $20. This makes the hobby much more accessible, but they have generated some controversy as they tend to not perform as well and can generate spurious emissions and other RF interference that a higher quality radio might not create. But one major benefit besides cost is that they’re great for tinkering around, as their simplified design is excellent for modifying. This experimental firmware upgrade changes a lot about this Quansheng model.

With the obligatory warning out of the way that modifying a radio may violate various laws or regulations of some localities, it looks like this modified firmware really expands the capabilities of the radio. The chip that is the basis of the radio, the BK4819, has a frequency range of 18-660 MHz and 840-1300 MHz but not all of these frequencies will be allowed with a standard firmware in order to comply with various regulations. However, there’s typically no technical reason that a radio can’t operate on any arbitrary frequency within this range, so opening up the firmware can add a lot of functionality to a radio that might not otherwise be capable.

Some of the other capabilities this modified firmware opens up is the ability to receive in various other modes, such as FM and AM within the range of allowable frequencies. To take a more deep dive on what this firmware allows be sure to check out the original GitHub project page as well, and if you’re curious as to why these inexpensive radios often run afoul of radio purists and regulators alike, take a look at some of the problems others have had in Europe.

Better Antennas Via Annealing (Simulated)

June 18, 2023 by 26 Comments

If you want to simulate a tic-tac-toe game, that’s easy. You can evaluate every possible move in a reasonable amount of time. Simulating antennas, however, is much harder. [Rosrislav] has been experimenting with using simulated annealing to iterate antenna designs, and he shares his progress in a recent blog post.

For many problems, it simply isn’t possible to try all possible inputs to determine what provides the “best” result. Instead of trying every single input or set of inputs, you can try random ones and discard all but the best guesses. Then you make small changes and try again. The only problem is that the algorithm may lock in on a “local maximum” — that is, a relatively high value that isn’t the highest because it forms a peak that isn’t the highest peak. Or, if you are looking for a minimum, you may lock on to a local minimum — same thing.

To combat that, simulated annealing works like annealing a metal. The simulation employs a temperature that cools over time. The higher the temperature, the more likely large changes to the input are to occur.

The Python program uses the PyNEC package to provide simulation. The program sets up random antenna lengths and finds the projected gain, attempting to optimize for maximum gain.

The post is long on code and short on details, so you will probably want to read the Python source to see exactly what it is doing. But it could probably serve as a template to do other simulated annealing simulations for other antennas or anything you had a simulation engine to evaluate.

Several techniques allow you to optimize things that are too hard to search exhaustively, and we’ve talked about simulated annealing and genetic algorithms before. However, lately, we’ve been more interested in annealing 3D prints.

Detecting Meteors With SDR

June 18, 2023 by 10 Comments

The simplest way to look for meteors is to go outside at night and look up — but it’s not terribly effective. Fortunately, there’s a better way: radio. With a software-defined radio and a little know-how from [Tech Minds], you can easily find them, as you can see in the video below.

This uses the UK meteor beacon we’ve looked at before. The beacon pushes an RF signal out so you can read the reflections from meteors. If you are too far from the beacon, you may need a special antenna or you might have to find another beacon altogether. We know of the Graves radar in France and we have to wonder if you couldn’t use some commercial transmitter with a little experimentation.

[Tech Minds] has some practical tips to share if you want to try doing it yourself. If you want to see what a detected meteor looks like, you can visit the UK beacon’s gallery page.

We saw another presentation on the UK beacon earlier this year. Using commercial transmitters sounds like it might be easy, but apparently, it isn’t.

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