I started to play with Z-Wave at home lately. I found an inexpensive Raspberry Pi Hat for that purpose which is simply called the RaZberry. It’s compatible with all the raspi models so far and it comes with the complete Z-Wave stack and exposes a WebUI + APIs to the user.
The main issue that I encountered was the range of the antenna, I had a lots of problems to reach devices that were few meters away from the controller just separated by a thin wall, and I hadn’t had any other devices working in that frequency range that could mess with it. It caused transient issues like delays in commands or difficulty to reach devices.
What I did is very simple, I just improved the onboard antenna by adding a copper cable of 1⁄4 of the Z-Wave wave-lenght.
To do so I first calculated the size of the antenna, according to the Z-Wave specs,
in Europe the frequency is 868.42MHz, so the wave-lenght is 300000⁄868420000 =
0.000345622 meters so divided by 4 it gives
Itook a thin copper cable of 86mm and soldered on top to SMD capacitor C7 (like on the picture above).
Results are great, I made few tests around the house and I can say that it improved
the coverage by at least a factor of 3. I guess that removing completely the on-board
antenna would improve it even more but I didn’t wanted to completely kill it in
the first time. Now that I’m confident with the setup I’ll simply cut the copper
track just after
A picture of the raspi + the Z-Wave hat and the home-made antenna.