Hello everyone,
Most Homey users are not technically experienced IT professionals or network administrators. In the community, people often recommend keeping Thread and Wi-Fi on different channels and choosing channels that are as far apart as possible. Some users then struggle with their router to move Wi-Fi to another channel—assuming their consumer router even allows manual channel selection. The situation becomes more complicated once multiple access points are involved.
Common mistakes
However, one of the most common mistakes comes from a basic misunderstanding of channel numbers.
For example, Homey Developer Tools may show that Homey has created its Thread network on channel 15. This may be different in your installation.
Warning: Do not change the Thread or Zigbee channel in Homey unless you fully understand the consequences. Changing it can cause devices to lose their connection and may require them to be recommissioned.
Now imagine that your router lets you choose between Wi-Fi channel 1 and Wi-Fi channel 11. Would you choose channel 1 because its channel number appears to be farther away from Thread channel 15?
That conclusion would be wrong.
The important detail is that we are comparing a Wi-Fi channel with a Thread channel. Wi-Fi and Thread channel numbers do not refer to the same frequencies. They use different numbering systems, even though both technologies operate in the 2.4 GHz frequency band.
Thread channel 15 has a centre frequency of 2425 MHz and a nominal range of approximately 2424–2426 MHz.
By comparison:
- Wi-Fi channel 1 at 20 MHz has a centre frequency of 2412 MHz and a nominal range of approximately 2402–2422 MHz.
- Wi-Fi channel 11 at 20 MHz has a centre frequency of 2462 MHz and a nominal range of approximately 2452–2472 MHz.
Two things immediately become clear.
First, a Thread channel is only about 2 MHz wide, while a 20 MHz Wi-Fi channel occupies a much wider part of the spectrum.
Second, Thread channel 15 is positioned very close to the upper edge of Wi-Fi channel 1, whereas it lies completely outside the nominal frequency range of Wi-Fi channel 11. Thread channel 15 is approximately 26 MHz away from the lower nominal edge of Wi-Fi channel 11.
Strictly speaking, Thread channel 15 does not fall inside the simplified nominal 20 MHz range of Wi-Fi channel 1; there is a small gap. However, real radio signals do not stop at perfectly sharp boundaries, so the larger separation provided by Wi-Fi channel 11 is still preferable.
The following two tables I’ve build show the Thread and 20 MHz Wi-Fi channels together with their centre frequencies and nominal frequency ranges.
I have made every effort to ensure that the tables are accurate, but I cannot accept responsibility for any errors, omissions, or consequences resulting from their use.
The 40 Ghz bandwith complexity
When the 2.4 GHz Wi-Fi channel width is set to 40 MHz, things become considerably more complicated.
No single 2.4 GHz Wi-Fi channel number represents a 40 MHz-wide channel by itself. Instead, Wi-Fi combines the selected primary channel with a secondary channel. The secondary channel is always four channel numbers away from the primary channel, corresponding to a 20 MHz difference between their centre frequencies.
But wait: if the secondary channel were four channels lower than Wi-Fi channel 1, it would have to be channel −3. If it were four channels higher than channel 13, it would have to be channel 17, which is not available.
Exactly.
This means:
- Primary channels 1–9 can use a secondary channel above.
- Primary channels 5–13 can use a secondary channel below.
- Primary channels 5–9 can theoretically use either direction.
And this is where the situation becomes even less transparent.
For channels 5–9, the secondary channel may be above or below the primary channel. Depending on the router, access point, firmware and automatic channel-selection logic, it may not always be obvious which direction is being used. Even some professional networking systems do not provide a simple manual setting for this.
Is that not complicated enough? Let us take it one step further.
Because a 40 MHz Wi-Fi channel combines two 20 MHz channels, the resulting centre frequency lies exactly halfway between the centre frequencies of the primary and secondary channels. The simplified nominal frequency range then extends approximately 20 MHz below and 20 MHz above that combined centre frequency.
For example:
- Primary channel 7 with secondary channel 11 gives a combined centre frequency of 2452 MHz.
- Primary channel 7 with secondary channel 3 gives a combined centre frequency of 2432 MHz.
The same primary channel can therefore occupy two completely different 40 MHz frequency ranges.
Because the secondary-channel direction for primary channels 5–9 is not always easy to control or identify, these combinations are often best avoided when predictable spectrum use is important.
For a network in which a narrow 2 MHz Thread channel should operate with as little interference as possible, I would therefore limit 2.4 GHz Wi-Fi to 20 MHz channel width.
TP-Link’s Omada guidance also generally recommends using 20 MHz in the 2.4 GHz band and reserving 40 MHz for carefully controlled environments where interference and neighbouring networks can be properly managed.
For completeness, and to make the relationship easier to understand, the following table shows the possible 40 MHz Wi-Fi channel combinations.
I have made every effort to ensure that the table is accurate, but I cannot accept responsibility for any errors, omissions, or consequences resulting from this use.
Adding Zigbee to the picture.
Wi-Fi is based on the IEEE 802.11 family of standards, whereas Thread and Zigbee both use IEEE 802.15.4 for their radio and medium-access layers.
In the 2.4 GHz band, Thread and Zigbee therefore use the same channel numbering, centre frequencies and nominal channel width. The values from the Thread table can be applied directly to Zigbee:
Channels 11–26
5 MHz spacing between channel centres
Approximately 2 MHz nominal channel width
The table could therefore be labelled Thread / Zigbee / IEEE 802.15.4 Channels.
On Homey Pro, Zigbee and Thread share the same radio hardware. In Homey’s current implementation, they operate on the same IEEE 802.15.4 channel, meaning that their nominal frequency ranges overlap completely. Athom also notes that resetting Homey’s Zigbee network resets its Thread network because both technologies share this hardware.
This does not necessarily mean that Zigbee and Thread cannot coexist. Both technologies normally transmit relatively small packets and generally have a low radio duty cycle. IEEE 802.15.4 also uses mechanisms such as Clear Channel Assessment, collision avoidance, acknowledgements and retransmissions. In simplified terms, the two networks compete for—or share—the available airtime.
However, sharing one radio and one channel gives both networks the same interference environment and leaves less room for avoiding local radio problems. Separate radio resources or dedicated hubs can place Zigbee and Thread on different channels. This does not guarantee better performance, but it provides more flexibility when planning a busy 2.4 GHz environment.
For an independent Zigbee network, such as one managed by a Philips Hue Bridge, I would therefore select a different IEEE 802.15.4 channel where possible.
Unlike adjacent 2.4 GHz Wi-Fi channels, the nominal 2 MHz Thread and Zigbee channels do not overlap with one another because their centre frequencies are spaced 5 MHz apart. Nevertheless, greater separation can still be useful because real radio emissions do not end at perfectly sharp boundaries.
When several Thread and Zigbee networks are operating in the same home, channel planning can quickly become difficult. You may need to separate several IEEE 802.15.4 networks from one another while also avoiding the much wider 2.4 GHz Wi-Fi channels.
The situation becomes even more complicated in networks with several Wi-Fi access points using different channels. The available clear spectrum can disappear surprisingly quickly.
Keeping Control of Channel Selection
When channel selection is left on Auto, it is easy to lose track of which frequencies are actually being used, especially in a network with several access points. Automatic channel changes can also create new overlaps with Thread or Zigbee without the user noticing.
In my own network, I therefore configured all 2.4 GHz access points manually to use the same Wi-Fi channel: channel 11. I selected channel 11 because my Homey Thread network operates on Thread channel 15, and Wi-Fi channel 11 provides much greater frequency separation from it than Wi-Fi channels 1 or 6.
Using the same Wi-Fi channel on every access point does mean that access points which can hear one another must share the available airtime. However, this is often preferable to using strongly overlapping Wi-Fi channels, which can create more disruptive adjacent-channel interference.
This approach works particularly well when:
- 2.4 GHz is mainly used for IoT and low-bandwidth devices;
- access points are located on different floors or sufficiently far apart;
- transmission power is adjusted so that neighbouring access points do not overlap excessively;
- high-bandwidth devices primarily use 5 GHz.
The goal is not to maximise 2.4 GHz speed, but to create a predictable and stable radio environment for Wi-Fi, Thread and Zigbee.
