Zigbee devices can't communicate reliably if they are too close to other electronics or objects which cause interference. Especially USB 3.0 devices are known to interfere with the 2.4 GHz based protocols such as Zigbee or Thread.
The video below demonstrates this effect: when the adapter is moved closely to a source of interference, the light switch and the light cannot communicate. The video shows a Home Assistant Connect ZBT-1 but the issue applies to any Zigbee adapter.
Technical note: The built-in IEEE 802.15.4 radio (like any Zigbee radio) uses a technique called Clear Channel Assessment (CCA). Before transmitting, the radio listens on the channel it intends to use. If there is traffic on the channel, it prevents the sender from becoming active. This traffic is not limited to the Zigbee protocol. It includes other protocols using the same 2.4 GHz band, as well as electromagnetic interference from other devices.
For an in-depth description of the issue, refer to the white paper issued in 2012 by Intel Corporation: USB 3.0* Radio Frequency Interference Impact on 2.4 GHz Wireless Devices
Countering interference
In some cases, the extension cable delivered with Home Assistant Connect ZBT-2 may not be sufficient to mitigate interference. If this occurs, try the following steps:
- Use a longer and/or shielded extension cable.
- Ensure the Home Assistant Connect ZBT-2 is not placed near any of the following objects:
- USB 3.0 and newer devices, hubs, or other transmitters (such as computers or routers)
- External SSDs or HDDs
- 2.4 GHz wireless devices, routers, or SBCs such as a Raspberry Pi
- thick walls
- wire mesh or metal (such as server rack housings or wall mounting brackets)
- body of water, such as an aquarium