You've positioned your router centrally, invested in a quality extender, and yet your WiFi still suffers mysterious slowdowns and dropouts. The culprit might be interference, invisible electromagnetic noise that disrupts your wireless signals. Understanding interference sources empowers you to identify and eliminate them, often dramatically improving your network performance without any new equipment.
How WiFi Interference Works
WiFi uses radio frequencies to transmit data wirelessly. In Australia and most countries, WiFi operates on the 2.4GHz and 5GHz frequency bands. When other devices emit signals on these same frequencies or create electromagnetic noise in these ranges, they can disrupt WiFi communications.
Interference manifests in various ways: reduced speeds, intermittent disconnections, high latency, or complete signal loss. The severity depends on the interference source's proximity, power, and how continuously it operates.
The Crowded 2.4GHz Band
The 2.4GHz band is particularly prone to interference because numerous devices share this frequency range. While 2.4GHz offers better range and wall penetration than 5GHz, this crowded spectrum often means worse real-world performance in interference-heavy environments.
Microwave Ovens
Microwave ovens operate at 2.45GHz, directly overlapping with WiFi channels. While properly shielded microwaves should contain their emissions, older or damaged units can leak significant interference. If your WiFi performance drops every time someone heats their lunch, the microwave is the likely culprit.
Solution: Keep your router and extender at least two metres from the microwave. If problems persist, consider having the microwave checked for shielding issues or replacing an older unit.
Cordless Phones
Many cordless phones, particularly older DECT models, use the 2.4GHz band. These phones transmit continuously while in use and periodically when idle, causing both active and background interference.
Solution: Upgrade to DECT 6.0 cordless phones, which use the 1.9GHz band and don't interfere with WiFi. Alternatively, position phone bases away from your router and extender.
Baby Monitors
Wireless baby monitors often operate on 2.4GHz and transmit continuously, creating persistent interference in their vicinity. Video monitors, which transmit more data, cause more interference than audio-only models.
Solution: Use baby monitors that operate on different frequencies, or position them as far as practical from your WiFi equipment. Some newer monitors use DECT or WiFi-based technology that coexists better with your network.
Common 2.4GHz Interferers
Microwave ovens, cordless phones, baby monitors, Bluetooth devices, wireless security cameras, wireless speakers, some fluorescent lights, and neighbouring WiFi networks all compete for space in the 2.4GHz band.
Bluetooth and WiFi Coexistence
Bluetooth also operates in the 2.4GHz band, and with the proliferation of Bluetooth devices from headphones to smart home sensors, interference has become increasingly common. Modern devices use frequency hopping and other techniques to minimise interference, but issues can still occur.
Bluetooth typically causes minor, intermittent interference rather than major disruptions. If you notice WiFi issues that correlate with Bluetooth activity, try using the 5GHz band for WiFi, which Bluetooth doesn't use.
Neighbouring WiFi Networks
In apartments and densely built suburbs, neighbouring WiFi networks often create the most significant interference. When multiple networks use the same or overlapping channels, they compete for airtime, reducing everyone's performance.
Understanding WiFi Channels
The 2.4GHz band has 13 channels in Australia, but they overlap significantly. Only channels 1, 6, and 11 are non-overlapping. If your network is on channel 3 and your neighbour's is on channel 4, they interfere more than if both used channel 6, where they'd at least share airtime fairly.
Finding the Best Channel
Use a WiFi analyser app (available free for smartphones) to scan nearby networks and see which channels are congested. On Android, apps like WiFi Analyzer show channel usage graphically. Choose the least congested non-overlapping channel (1, 6, or 11) for your network.
For 5GHz, there are many more non-overlapping channels, and interference from neighbours is typically less problematic. However, 5GHz signals don't penetrate walls as well, so neighbouring networks have less opportunity to interfere anyway.
Auto Channel Selection
Most modern routers can automatically select the best channel. However, they typically only do this on startup. Try rebooting your router during off-peak hours when you can scan the WiFi environment. Some routers offer scheduled auto-channel selection.
Physical Interference Sources
Not all interference is electromagnetic. Physical objects can block, absorb, or reflect WiFi signals, creating effective dead zones.
Water
Water absorbs WiFi signals very effectively. Large fish tanks, water heaters, and even human bodies (which are mostly water) can significantly attenuate signals. If your router is behind a large aquarium, performance will suffer.
Metal Objects
Metal reflects and blocks WiFi signals. Large metal objects like filing cabinets, refrigerators, and metal-framed furniture can create shadow zones behind them. Metal-lined insulation or foil-backed building materials can severely limit signal propagation.
Mirrors
Mirrors have a thin metal backing that reflects WiFi signals just as it reflects light. Large mirrors can create unusual reflection patterns, sometimes causing signals to reach unexpected areas while blocking the direct path.
Interference Reduction Strategies
- Switch to 5GHz band when possible to avoid 2.4GHz congestion
- Keep router/extender away from microwaves and cordless phones
- Use a WiFi analyzer to find the least congested channel
- Move networking equipment away from large metal objects and water
- Consider the 6GHz band (WiFi 6E) for interference-free operation
Less Obvious Interference Sources
LED Lights and Dimmers
Some LED bulbs and dimmer switches generate electromagnetic interference that affects WiFi. This is more common with cheaper LED bulbs and older dimmer designs. If WiFi issues correlate with lighting changes, try replacing bulbs or using different dimmer models.
USB 3.0 Devices
USB 3.0 ports and cables can emit interference in the 2.4GHz range, particularly affecting nearby WiFi equipment. If your router has USB 3.0 ports with devices attached, try using shielded cables or repositioning USB devices away from the router's antennas.
Power Lines and Electrical Equipment
Electrical wiring, particularly older unshielded wiring, can carry interference. Power strips, UPS units, and other electrical equipment near your router may create noise. Maintaining distance between networking equipment and major electrical sources often helps.
Diagnosing Interference Problems
Systematic troubleshooting helps identify interference sources:
- Note when problems occur. Are they constant or intermittent? Do they correlate with specific activities or times?
- Test both 2.4GHz and 5GHz bands. If only 2.4GHz is affected, the interference source likely operates on that frequency.
- Use a WiFi analyser to check for competing networks and noise levels on different channels.
- Temporarily power off suspected interference sources one at a time while monitoring WiFi performance.
- Move your router or extender and observe if performance changes, which may indicate physical interference from objects in the original location.
Once you identify interference sources, you can take targeted action, whether that's relocating equipment, changing channels, switching bands, or eliminating the interference source itself. Often, simple changes based on understanding interference can provide more improvement than expensive equipment upgrades.