LoRa

93 Articles

Tiny LoRa GPS Node Relies On ESP32

October 17, 2024 by 10 Comments

Sometimes you need to create a satellite navigation tracking device that communicates via a low-power mesh network. [Powerfeatherdev] was in just that situation, and they whipped up a particularly compact solution to do the job.

As you might have guessed based on the name of its creator, this build is based around the ESP32-S3 PowerFeather board. The PowerFeather has the benefit of robust power management features, which makes it perfect for a power-sipping project that’s intended to run for a long time. It can even run on solar power and manage battery levels if so desired. The GPS and LoRa gear is all mounted on a secondary “wing” PCB that slots directly on to the PowerFeather like a Arduino shield or Raspberry Pi HAT. The whole assembly is barely larger than a AA battery.

It’s basically a super-small GPS tracker that transmits over LoRa, while being optimized for maximum run time on limited power from a small lithium-ion cell. If you’re needing to do some long-duration, low-power tracking task for a project, this might be right up your alley.

LoRa is a useful technology for radio communications, as we’ve been saying for some time. Meanwhile, if you’ve got your own nifty radio comms build, or anything in that general milleu, don’t hesitate to drop us a line!

WiFi Meets LoRa For Long Range

October 7, 2024 by 20 Comments

What do you get when you cross WiFi and LoRa? Researchers in China have been doing this, and they call the result WiLo. They claim to get reliable connections over about half a kilometer. Typical WiFi runs 40 to 60 meters, barring any Pringle’s cans or other exotic tricks.

According to [Michelle Hampson] writing in IEEE Spectrum, the researchers manipulated Wi-Fi’s OFDM multiplexing to emulate LoRa’s chirp-spreading signal. The advantage is that existing WiFi hardware can use the protocol to increase range.

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Decoding Meshtastic With GNU Radio

June 26, 2024 by 20 Comments

Meshtastic is a way to build mesh networks using LoRa that is independent of cell towers, hot spots or traditional repeaters. It stands to reason that with an SDR and GNU Radio, you could send and receive Meshtastic messages. That’s exactly what [Josh Conway] built, and you can see a video about the project, Meshtastic_SDR, below. The video is from [cemaxecuter], who puts the library through its paces.

For hardware, the video uses a Canary I as well as the WarDragon software-defined radio kit which is an Airspy R2 and a mini PC running Dragon OS — a Linux distribution aimed at SDR work —  in a rugged case. GNU Radio, of course, uses flows which are really just Python modules strung together with a GUI.

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Passive Diplexer Makes One Antenna Act Like Two

May 22, 2024 by 24 Comments

Stay in the amateur radio hobby long enough and you might end up with quite a collection of antennas. With privileges that almost extend from DC to daylight, one antenna will rarely do everything, and pretty soon your roof starts to get hard to see through the forest of antennas. It may be hell on curb appeal, but what’s a ham to do?

One answer could be making one antenna do the work of two, as [Guido] did with this diplexer for dual APRS setups. Automatic Packet Reporting System is a packet radio system used by hams to transmit telemetry and other low-bandwidth digital data. It’s most closely associated with the 2-meter ham band, but [Guido] has both 2-meter (144.8-MHz) and 70-cm LoRa (433.775-MHz) APRS IGates, or Internet gateway receivers. His goal was to use a single broadband discone antenna for both APRS receivers, and this would require sorting the proper signals from the antenna to the proper receiver with a diplexer.

Note that [Guido] refers to his design as a “duplexer,” which is a device to isolate and protect a receiver from a transmitter when they share the same antenna — very similar to a diplexer but different. His diplexer is basically a pair of filters in parallel — a high-pass filter tuned to just below the 70-cm band, and a low-pass filter tuned just above the top of the 2-m band. The filters were designed using a handy online tool and simulated in LTSpice, and then constructed in classic “ugly” style. The diplexer is all-passive and uses air-core inductors, all hand-wound and tweaked by adjusting the spacing of the turns.

[Guido]’s diplexer performs quite well — only a fraction of a dB of insertion loss, but 45 to 50 dB attenuation of unwanted frequencies — pretty impressive for a box full of caps and coils. We love these quick and dirty tactical builds, and it’s always a treat to see RF wizardry in action.

A Long-Range Meshtastic Relay

April 3, 2024 by 22 Comments

In the past few years we’ve seen the rise of low-power mesh networking devices for everything from IoT devices, weather stations, and even off-grid communications networks. These radio modules are largely exempt from licensing requirements due to their low power and typically only operate within a very small area. But by borrowing some ideas from the licensed side of amateur radio, [Peter Fairlie] built this Meshtastic repeater which can greatly extend the range of his low-power system.

[Peter] is calling this a “long lines relay” after old AT&T microwave technology, but it is essentially two Heltec modules set up to operate as Meshtastic nodes, where one can operate as a receiver while the other re-transmits the received signal. Each is connected to a log-periodic antenna to greatly increase the range of the repeater along the direction of the antenna. These antennas are highly directional, but they allow [Peter] to connect to Meshtastic networks in the semi-distant city of Toronto which he otherwise wouldn’t be able to hear.

With the two modules connected to the antennas and enclosed in a weatherproof box, the system was mounted on a radio tower allowing a greatly increased range for these low-power devices. If you’re familiar with LoRa but not Meshtastic, it’s become somewhat popular lately for being a straightforward tool for setting up low-power networks for various tasks. [Jonathan Bennett] explored it in much more detail as an emergency communications mode after a tornado hit his home town.

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LoRA, With No Radio

March 29, 2024 by 29 Comments

A LoRa project has traditionally required a dedicated radio module, because it’s a commercially licenced protocol. But as the way it works has been progressively reverse engineered, it’s become ever more possible to produce a LoRA radio for yourself. But what about a LoRA radio without a radio at all? [CNLohr] has managed just that, by driving a microcontroller pin and relying on one of its harmonics to provide enough RF to be received by a LoRA gateway.

The video below the break goes into the process in great detail, revealing some of the tricks. Undersampling to create intentional aliasing for example allows subharmonic peaks to be produced in unexpected places. Most of the development is performed on Espressif microcontrollers, but as the code is optimised it becomes possible to use it on much more modest silicon. The dirt cheap CH32V003 RISC-V microcontroller for example can be a LoRA transmitter able to talk to a gateway at a range of hundreds of metres with the CH32 and 2.5km with the ESP32. The code can be found in this GitHub repository.

The CH32 can’t receive of course, and it relies on barfing harmonics all over the spectrum to work. But on the other hand its total RF output is so tiny that we’re guessing a filter for the LoRA band might even make it almost legal. He’s got a little way to go before beating the record though.

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A portable digital radio transceiver in a 3d printed case

RNODE: A Portable Unrestricted Digital Radio

March 18, 2024 by 10 Comments

RNode is an open source, unrestricted digital radio transceiver based on — but not limited to — the Reticulum cryptographic networking stack. It is another interesting project in what we might call the “Federated application” space in that it is intended to be used with no central controlling body. It can be used in a LAN or WAN context with the Reticulum network when operating in network adaptor mode, but it also has other use cases.

Essentially, RNode is a software project running on a LilyGO LoRa32 board wrapped up in a snazzy-looking 3D-printed case. Just make sure to grab a version of the board with an u.FL connector in place or somewhere to solder one. If it comes with an SMA connector, you will want to remove that. The device can be standalone, perhaps attached to a mobile device via Wi-Fi, but it needs to be hooked up to a laptop for the really interesting applications. When set to TNC mode, it can act as an APRS gateway, which allows you to access packet radio BBSs and all that fun stuff.

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