Denver Mesh is a community group working to build a mesh network of solar-powered meshtastic radios in Denver, Colorado. This network acts like a city-wide text messaging system, allowing people to communicate publicly or privately with anyone on the network. All of this happens without any external infrastructure - no power, no cell phone towers, no internet.
How does it work?
We're working to set up solar-powered radio repeaters in Denver. These radios communicate on the 915 MHZ frequency using the LoRa protocol.
The radios mesh 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.
Denver Mesh works the same way as this paper example, but instead of sending paper notes we're using digital text messages and sending it with radio waves. Our radios are solar powered and they don’t need any 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: Denver Mesh is decentralized - there is no central server or corporation - all the communication bounces through the entire mesh. Denver Mesh is open to everyone - you don't have to ask permission to join and all of the software is open-source. Denver 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 Winter 2023 we're setting up our first nodes and looking to provide connectivity to the Capitol Hill area.
How can I join the network?
1) Get a Meshtastic Radio.
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 I can join the group?
You can email us at [email protected]. We're still figuring out what participation looks like so look for more information on meetups and social media soon!
Building a Solar-Powered Repeater
Here's the parts list that Austin Mesh came up with as their 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 V25 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 than 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. Right now they're testing the V25 battery which has 6,400 mAh, but if we were going to install a node in a very hard-to-reach place we’d probably use the larger V75 19,200 mAh battery.
The RAK radio uses between 100 and 1000 mAh per day, with about 400 mAh per day being average so theoretically the Voltaic V25 could keep the radio working for 16 days without any solar power and the V75 could keep the radio running for 48 days without solar.
Voltaic Systems V25
RAK Meshtastic Kit
IPEX to N Type Female
915 MHz 3 dBi N-Female
ABS Box, 200mm x 120mm x 75mm
USB Cable Pass-Through
3/4 NPT Cable Gland
Comparing it to APRS on Ham Radio
For people who are familiar with using the Automatic Packet Reporting System (APRS) on ham radio, Meshtastic is similar in a few ways:
Digipeaters: APRS radios can be set up as clients, which receive all messages and only transmit the users messages, or APRS radios can be set up as digipeaters, which repeat all the messages they hear. Meshtastic radios by default all act as repeaters – just like APRS digipeaters.
iGates: MQTT Gateways are like APRS iGates – they repeat all local traffic over the internet to other MQTT Gateways around the world.
ANSRVR: APRS users can subscribe to groups using the ANSRVR service. This allows for group chats like the popular #APRSThursday net. Meshtastic has “Secondary Channels” that can be subscribe to, allowing users to send messages to everyone on the channel.
Burst Communication: APRS uses the AX.25 protocol which sends messages using data bursts between 0.3 and 0.5 seconds long. Meshtastic uses the LoRa protocol which sends messages in data bursts between 0.5 and 10 seconds long.
But Meshtastic is also different than APRS in a few ways:
Primary Channel: APRS doesn’t have a way to broadcast a message to everyone on the network. Messages sent to Meshtastic's Primary Channel go to everyone.
Encryption: APRS is unencrypted because it is illegal to use encryption over ham radio. Meshtastic is encrypted for communications on private group channels and for direct messages between users, because it runs on the 900 MHz ISM band, which does not have restrictions on encryption.
License: APRS requires the user to have a ham radio license. Meshtastic does not require any license and is open for anyone to use.
Equipment Cost: APRS capable handheld ham radios cost upwards of $400. Meshtastic radios cost less than $100.
Email and SMS: APRS has services which allow users to send emails and SMS text messages to people who aren’t ham radio users. Meshtastic does not have this feature but it could be added in the future.
Simplicity: APRS is quite a bit more difficult to use than Meshtastic. APRS does not have any standardized user interface – there are dozens of software packages available. Meshtastic has a standardized iPhone and Android app which is easy to understand for new users.
This site is © by Tyson Vinson and is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. Contents copied liberally from the Austin Mesh site © Will Martin Creative Commons Attribution-ShareAlike 4.0 International License.