What is the 2.4 GHz band?
The 2.4 GHz band is the Wi-Fi band with the widest device support. It is unlicensed ISM (industrial, scientific and medical) spectrum, so Wi-Fi shares it with Bluetooth, microwave ovens, some cordless phones, baby monitors and many smart-home devices. Dual-band and tri-band routers still include a 2.4 GHz radio alongside their 5 GHz (and 6 GHz) radios.
Channels
The band is divided into channels spaced 5 MHz apart, but a Wi-Fi channel is about 20 MHz wide, so neighboring channels overlap.
- United States: Wi-Fi equipment uses channels 1 through 11.
- Much of the rest of the world: channels 1 through 13. Channel 14 is permitted only in Japan and only for 802.11b.
- Non-overlapping channels: 1, 6 and 11. Neighboring access points should use these three, not channels in between such as 3 or 9, which overlap two of them.
- Channel width: stay at 20 MHz. A 40 MHz channel takes up most of the band and overlaps nearly every network around it.
Strengths and weaknesses
| Strengths | Weaknesses |
|---|---|
| Longer range than 5 or 6 GHz at the same transmit power | Lower throughput, with only three non-overlapping 20 MHz channels |
| Passes through walls and floors better | Crowded in apartments and offices, which causes co-channel and adjacent-channel interference |
| Supported by almost every Wi-Fi device, including many IoT devices that have no 5 GHz radio | Interference from microwave ovens, Bluetooth, cordless phones and other non-Wi-Fi devices |
Standards that use 2.4 GHz
- 802.11b: up to 11 Mbps, 2.4 GHz only.
- 802.11g: up to 54 Mbps, 2.4 GHz only.
- 802.11n (Wi-Fi 4): 2.4 GHz and 5 GHz.
- 802.11ax (Wi-Fi 6): 2.4 GHz and 5 GHz; Wi-Fi 6E adds 6 GHz.
802.11a and 802.11ac (Wi-Fi 5) do not use 2.4 GHz. On a Wi-Fi 5 router, the 2.4 GHz radio runs 802.11n.
Troubleshooting cues
- Wi-Fi slows or drops when the microwave runs: 2.4 GHz interference. Move the client to 5 GHz, change the channel, or move the access point away from the source.
- Many networks show up on the same or overlapping channels: use a Wi-Fi analyzer and pick the least crowded of 1, 6 and 11.
- A smart plug or camera will not join the network: it may support only 2.4 GHz. Make sure the 2.4 GHz radio is on, and consider a separate 2.4 GHz SSID if band steering gets in the way during setup.
- A client at the edge of coverage keeps a weak 5 GHz connection: 2.4 GHz may give a more stable link at that distance.
- Bluetooth audio stutters while a laptop is on 2.4 GHz Wi-Fi: both share the same band; moving the laptop to 5 GHz often helps.
2.4 GHz band on the CompTIA A+ exam
Core 1 objective 2.2 lists the 2.4GHz, 5GHz and 6GHz frequencies, channels (regulations and channel selection, including widths, frequencies and bands) and the 802.11 standards. Expect to compare bands: 2.4 GHz means better range and penetration but lower speed and more interference, and 1, 6 and 11 are its non-overlapping channels. If a question mentions microwave ovens, Bluetooth interference or an old 802.11b/g device, think 2.4 GHz. If it asks for the fastest connection close to the access point, the answer is usually 5 or 6 GHz instead.