Meshtastic

January 2025

The presentation at 38C3, “Hacker’s Guide to Meshtastic: Off-Grid, Encrypted LoRa Meshnets for Cheap!” got me to take a look at what was happening with Meshtastic in my region. With two borrowed nodes, one in the window and the other in my hand, I was able to try out the range test function. At that point, I hadn’t received any nodes nearby. The mobile Meshtastic node was a Heltec V1 in a Muzi Works H1 case. I didn’t need the small OLED display, and with the high power consumption of an ESP32, the battery was empty after half a day. In the meantime, other nodes appeared here and there, and the list became particularly full if someone had one with them on an airplane. Proper communication did not yet take place, but the potential of such a mesh network for short messages was evident.

With my following requirements:

As small as possible
Battery Lifetime at least 24h

I bought myself a RAK19003 WisBlock Mini Base Board with a RAK4631 WisBlock LoRaWAN Module. The battery should not be much larger than the base board. A 500mAh LiPo cell (41 x 30 x 4mm) had the same width and should last longer than 2 days with its capacity. It is important to ensure that a protective circuit is present, as the base board has a charge controller but does not otherwise care about the health of the battery. Since a smartphone with the Meshtastic app is required for operation, a power bank is needed after two days when camping anyways.

The “WisBlock Meshtastic Starter Kit” as EU 800MHz version came with two PCB antennas. One with the gray cable for 2.4GHz (Bluetooth), the other for LoRa. I assumed that the included antenna would work reasonably well. Unfortunately, I found that under the same conditions, the range test was already over after 50 meters. Previously, I was able to reach a field 2km away even with the Heltec V3 and cheap antennas.

The same order included a “Heltec Meshtastic ESP32-S3 V3 Wireless Stick”, which I wanted to install as a base node in the window. It came with a small coil antenna, which, as I was later able to measure with a VNA, was not perfectly tuned to 869.525 MHz, but significantly better. For the target size I am aiming for a 1/4 lambda antenna is too long, so this coil antenna was good enough for me.

After several iterations, the following housing was created for the components mentioned. The circuit board is simply inserted and held in place by the battery and cover. There is a hole at the front for the USB-C port, as well as smaller holes for LEDs and the user button. This button can be reached with a small piece of wire, but I have never needed it so far. To the left of the circuit board is a slot into which the Bluetooth antenna is inserted. The range wasn’t that important to me, but I’m still connected to the node throughout my entire apartment. I wasn’t sure how much the proximity to the circuit board would affect the range of the LoRa antenna. That’s why it was made foldable. Other features include a tab for a carrying strap or cable ties. A cable tie has proven to be quite useful for temporarily attaching the box to higher places, such as a bicycle or jacket. Two slots on the bottom allow magnets to be inserted. This allows the Node to be attached to railings.

The case was printed out of transparent PETG with minimal supports.

Between the battery and the JST-PH2.0 plug a switch is soldered, since there would be otherwise no way to turn the node off or restart it.

A small metal pin is used to attach and create a pivot for the antenna.

First insert the circuit board. Then move the Bluetooth antenna into place. Now the u.fl connector of the LoRa antenna can be plugged into the RAK module. Place a piece of tape on top as a barrier between the sharp edges of the antenna connector and the sensitive LiPo. The on/off switch is attached directly above the USB-C port and held in place by a hole in the cover. This ensures that it is flush and cannot be accidentally pressed in.

Four small screws from my miscellaneous screw box were perfect to secure the cover.

And thats my mobile Meshtastic node which I usually carry around.