What is it?

Birmingham Mesh is a community group in Birmingham, Alabama working to create a mesh network of solar-powered Meshtastic radios.

This network acts like a city-wide text messaging system, allowing people to communicate publicly or privately with anyone on the mesh network. ALSO, NO LICENSE IS REQUIRED!

All of this happens without any external infrastructure – no commercial power or cell phone towers. The mesh network can utilize the Internet, but does not require the Internet.

How does it work?

We are setting up a number of solar-powered radio repeaters in Birmingham. These radios communicate on 906.875 MHz using the https://en.wikipedia.org/wiki/LoRa

The radios automatically mesh together with other Meshtastic devices using the open-source Meshtastic software.

Users can connect to these repeaters by Bluetooth if they’re close enough, or they can use their own handheld nodes which will also act as repeaters. The messages hop from node to node, extending the reach of the network and ensuring everyone receives every message.

Can you explain it like I’m 5?

Pretend you’re sitting in class and want to send a note to everyone in the class. You write your note on a piece of paper and copy it three times. The message can be up to 228 characters – about as long as this paragraph so far. You hand those three pieces of paper to the three people around you. Then those three people re-write the message three times and hand it to the three people around them and so on. Now imagine a big gust of wind comes and blows away some of the messages. If even just a few people saw the note and keep copying and re-sending it, eventually everyone will get a copy of the note. This is like sending an unencrypted message to everyone on the network.

Now imagine you want to send a message to a single person or a select group of people but you don’t want other people who see the note to be able to read it. You could write the note using a secret language. You could then hand a decoder key to your friend or to a group of friends and they could decode the message. The message still gets passed the same way – with every single person writing the message a few times and handing it to everyone – but only those people with the decoder key will be able to understand the message. This is like sending an encrypted direct message or encrypted group message.

Birmingham Mesh works the same way as this paper example, but instead of sending paper notes, we are using digital text messages and sending it with radio waves. Our radios are solar powered and they don’t need any i\Internet or cell phone coverage. This means they will work even if the power is out.

What can it do?

Meshtastic is a bit like a decentralized social media platform or SMS text messaging. It has a number of different features which will be familiar to anyone who has sent a text message or posted on social media.

1) Primary Channel:

You can broadcast an unencrypted message to the Primary Channel and everyone on your mesh will see it. This is a bit like “posting” publicly on a social media platform.

2) Group Channels:

You can send an encrypted message to a select group of people on a Secondary Channel and everyone who is subscribed to that channel will get it. People can join the channel if you provide them with an encryption key which you can send to them via Direct Message or which they can scan from a QR code in person. This is a bit like a private group on social media, or a group text message chain on SMS.

3) Direct Messages

You can send encrypted direct messages to people on the mesh. This is like a private text message or a DM on social medial.

4) Location:

If you choose to enable it you can send your location to the mesh and it will show up on everyone’s map in the app.

5) Connect Worldwide:

If anyone on your local mesh is running an MQTT gateway, your local mesh will connect to the other meshes around the world. This can allow you to broadcast messages to everyone globally or send encrypted messages to groups or individuals worldwide.

6) Telemetry Data:

Nodes can be set up to send telemetry data like the battery status or signal strength, which is helpful for monitoring remote solar-powered nodes. Nodes can also have sensors connected to them which allow them to send data on temperature, humidity, or air pressure which allow them to act like weather stations.

Why build this network?

1) Community:

Because this is essentially a city-wide group text message chain, we are hoping people use the network to build community. Tell the group where your band is playing tonight, chat about local politics, ask for a good cheese dip recipe, etc.

2) Disasters:

If the power goes out, this network should allow people to continue to communicate with each other without electricity, cell phone coverage, or Internet. This big city-wide group text chain could allow people to ask for help or offer assistance. People could get information about where warming centers are open or ask who in their neighborhood still has power. People could also send encrypted direct messages to check in on friends and family or they could send encrypted group messages to coordinate privately in a group.

3) Decentralized, Open, and Resilient:

Birmingham Mesh is decentralized – there is no central server or corporation – all the communication bounces through the entire mesh. Birmingham Mesh is open to everyone – you don’t have to ask permission to join and all of the software is open-source. Birmingham Mesh is resilient – our solar-powered radios don’t need cell phone towers, internet access, or electricity. We hope this project will inspire others to build things that are decentralized, open, and resilient.

What kind of coverage does the mesh network have?

As of Summer 2024, we are in phase I of our initial deployment, and working to establish coverage around the I-65 corridor from Homewood, to Hoover, to Pelham, to Alabaster and Chelsea. We’re actively working to expand this coverage area into downtown Birmingham and Bessemer as well.

We’ll be deploying a Birmingham Mesh Node map here soon, so keep checking back.

How can I join the network?

1) Get a Meshtastic Radio capable of operating on 915 MHz (NOT 433 MHz AND NOT 866 MHz), then pair it with your smartphone via Bluetooth.

You can build one yourself for about $35. The official Meshtastic page keeps a current list of Supported Hardware. The LILYGO T-Echo is a good first Meshtastic radio, as it costs around $70 and is ready to go out of the box (besides having to flash the firmware).

You can also buy a pre-built battery-powered radio for between $50-$100 on Etsy or eBay – these usually have 3D printed cases.

If you can afford it, and have a place to mount it outside, we recommend you buy a pre-built solar-powered node for between $100 and $200 on Etsy and mount it as high off the ground as you can.

2) Download the Meshtastic App on your iPhone or Android.

3) Pair your radio to your phone with Bluetooth.

4) Open the Meshtastic app and say hi!

How can I join the group?

You can email us to become an official member and attend our in-person meetings in Birmingham. You can also follow us on Twitter,

Our friends at AustinMesh.org have tried 5 permutations of solar powering nodes:

Version 1.0: Using RAK RAKBox-B2 Enclosure with solar panel. The panel was connected directly to the RAK Wireless WisBlock Meshtastic Starter Kit US915. We connected a 2000 MAh Lithium Polymer battery directly to the RAK board. We drilled a hole in the top of the box and attached a fiberglass antenna, which was connected to the RAK board with an iPEX to N-Type connector. We mounted this on top of one of the UT buildings and it died within a month. The 0.4 watt panel is way too small.

Version 2.0: Same as 1.0 but we added a second 5 watt solar panel that was connected to the RAK board via USB. Also died within a month.

Version 3.0: To minimize the number of components outside the box we used a much larger box with a clear lid and placed the solar panel inside the box. We added a Texas Instruments Green Power Module between the solar panel and the RAK board to help regulate the power. For batteries, we switched to using four 18650 batteries and we also added an over-discharge protection circuit from Voltaic Enclosures (not to be confused with Voltaic Systems) between the battery and the RAK board to provide clean shutoff when battery voltage fell below 2.5v. We mounted this on top of the UT buildings and it died in 3 months.

Version 4.0: Same as Version 3.0 but we mounted the solar panel outside of the box (using a smaller box). We mounted this on a pole and it died within 3 months.

Version 5.0: For this version, we stopped using the RAK’s solar and battery connectors entirely. Instead, we connected a large 12 watt solar panel to a Voltaic Systems battery via USB and then connected the battery to the RAK board via USB. The Voltaic Systems battery acts as the solar charge controller and also acts as the over-discharge protection circuit; the battery will charge at a range of voltages from the solar panel (if it gets shaded) and the battery will shut off if the voltage drops too low and will reboot itself once it has recharged sufficiently.

Lessons learned:

Don’t trust the RAK board to handle varying solar voltage or varying battery voltage. It is very unhappy if either voltage goes outside of a narrow range. In fact, there is a known issue where the Nordic nRF52840 module inside of the RAK 4631 chip causes it to enter a “Super Deep Sleep” fault state when it is supplied with 3.3V. This means when the battery voltage falls too low the RAK chip shuts down and can only be rebooted manually.
Solar panels: bigger is better. 10 watts or more is ideal.
Battery: bigger is better. 10,000 mAh or more is ideal.
Antenna: fiberglass antennas are the most robust and can handle wind, rain, and UV light better than rubber ducky antennas.
Heat can kill the battery – it is best to shade the box containing the battery.
Don’t add any modules. The GPS module increases battery usage significantly and is unnecessary if the repeater is in a fixed position.
Seal everything properly and make sure water has a way to get out of the case. Use o-rings for the antenna mount and wrap connectors in Proxicast. Add a drain plug to the case so any condensation has a way to escape. For high humidity environments, spray the electronics with conformal coating.

These are lessons learned from Birmingham, Texas, where the main environmental stressors are heat and thunderstorms. In the summer of 2023, we had 80 days over 100°F (38°C) and we had a stretch of 11 days over 105°F (40.5°C), during which two radios died. We also can have both high humidity and high temperature at the same time in Birmingham; in the summer the weather would swing from 80°F (27°C) with 85% humidity in the morning to 105°F (38°C) with 25% humidity in the afternoon. Our learnings are probably applicable to other southern and desert climates.

Considerations for other climates:

Northern Climates: At higher latitudes, there is much less sunshine in the winter. A larger solar panel would be necessary and angling the panel lower to the horizon would be beneficial. The rule of thumb is to angle the solar panels at the same degree as your latitude. In Birmingham, our panels should be angled at 30° but in Calgary, the optimal angle would be 50°. Batteries should also be bigger in colder climates as low temperatures reduce their performance.
Coastal Climates: salt spray and condensation from fog can kill electronics quickly. In coastal climates, it is best to spray the electronics with conformal coating.

With all that said, here is the parts list for our most-preferred way to build a solar-powered repeater. This design doesn’t require any soldering or complicated connectors. It also doesn’t require any battery management chips (which often have long shipping lead times and can be hard to get). For this design, the solar panel is connected directly to the battery pack via USB. Then the battery pack is connected to the board via USB. The Voltaic Systems V75 battery is nice because it is optimized to charge from a solar panel and it is set standard to an “always on” mode which means the battery bank does not shut off after a set amount of time like other battery packs – this is useful as the RAK chip uses very little power and can trick other battery packs into shutting off. The other really nice thing about the Voltaic pack is that when it drains down completely it shuts down, but then once the solar panel has sufficiently charged it back up it will automatically turn itself back on again.

The RAK radio uses between 100 and 1000 mAh per day, with about 400 mAh per day being average so theoretically the 19,200mAh Voltaic V75 could keep the radio running for 48 days without solar.