LoRa

91 Articles

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 20 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 28 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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Custom Library Rescues Good LoRa Hardware From Bad Firmware

March 13, 2024 by 17 Comments

The range of hardware that comes on some dev boards these days is truly staggering. Those little LoRa boards are a prime example — ESP32 with WiFi and Bluetooth, a transceiver that covers a big chunk of the UHF band, and niceties like OLED displays and plenty of GPIO. But the firmware and docs? Well, if you can’t say something nice, don’t say anything at all. Or better yet, just roll your own.

Of course that doesn’t hold true for all the LoRa dev boards on the market, but [Rop] certainly found it to be the case for the Heltec HTIT-WB32LA. This board has all the bells and whistles and would be perfect for LoraWAN and Meshtastic applications, but it needed a little help getting it over the line. [Rop]’s contribution to this end is pretty comprehensive and is based on his fork of the RadioLib library, which incorporates a library that greatly reduces wear on the ESP32’s flash memory. In addition to full radio support, the library supports all the hardware on the board from the pushbutton to the display, power management and battery charging, and of course the blinkenlights.

[Jop] includes quite a few example applications, from the bare minimum needed to get the board spun up to a full-blown spectrum analyzer. It’s a nice piece of work, and a great give-back to the LoRa community. And if you want to put one of these modules to work, you’re certainly in the right place. We’ve got everything from LoRaWAN networks to the magic of Meshtastic, so take your pick and get hacking.

Garden Light Turned Mesh Network Node

January 21, 2024 by 11 Comments

We love a good deal, especially when it comes to scavenging parts for projects. Cheap outdoor solar lights are more than just garden accessories; they’re a handy source of waterproof enclosures, solar panels and batteries. This is demonstrated by [Tavis], who turned one such light into a Meshtastic LoRa communication node.

Solar Light With Meshtastic node inside
Where there’s an antenna, there’s a radio

A nice feature on this specific $15 Harbor Breeze Solar LED is the roomy solar panel enclosure with integrated 18650 battery holder, allowing for easy battery swaps. [Tavis] was able to easily fit the RAKwireless modular dev board, and wire it into the light’s charging circuit. The cheap  circuit is likely not the most efficient, but will probably get the job done. It’s always possible to just swap it out with a better charging board. [Tavis] also added an external antenna by using a panel-mount SMA pigtail connector.

The Meshtastic project is all about enabling text-only communications through LoRa-based mesh networks, built using off-the-shelf devices and development boards that won’t break the bank. The project has seen some incredible growth, with people all over the world setting up their own networks.

It’s not the first time we’ve seen garden lights get used in project. We’ve seen MQTT added to a PIR solar light with some clever power saving circuitry, and as a power source for Attiny85-based projects.