The Causes of Wireless Interference

By Andy Walton

Wireless interference can make getting online hard work.
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Wireless interference -- when the signal from a Wi-Fi device is obstructed as it travels through the air -- is a key cause of slow or unstable wireless connections, making even the simplest online tasks a chore to perform. With more and more household devices using Wi-Fi as a networking tool, it's never been more important to understand why wireless interference occurs and what can be done to prevent it.

Building Construction

Certain construction materials can cause interference by absorbing or reflecting the radio waves that make up a wireless signal. For example, metals, concrete and ceramics are all known to degrade waves that pass through them, and should be kept out of Wi-Fi signal paths. Sometimes interference-causing materials can be hard to spot, as with the lead paint on the walls in some older buildings. Even a thin layer of lead can cause a severe amount of wireless interference.

Electronic Devices

Many common electronic devices emit radio waves, often in the same frequency bands as those used by Wi-Fi routers and access points. This can cause clashes with wireless signals. Some of these devices are designed to communicate wirelessly themselves, like cordless phones and Bluetooth headsets, but devices like microwaves and LCD monitors can also interfere with wireless signals. Placing your router as far away from these devices as possible will help to optimize your wireless connection.

External Factors

Wireless interference can be generated by factors outside the home or office, often related to the construction or utility industries. Power lines can often interfere with Wi-Fi signals, as can broadcast television masts or cameras. Overhead cranes or scaffolding can also cause wireless disruption, as these are usually made of metal. Even natural phenomena can generate interference -- trees with large leaves can block Wi-Fi signals due to the signal being broken up by water contained in the plant.


Sometimes, wireless signals become distorted because of the sheer distance they need to travel. This is due to a process known as attenuation, whereby the strength of a signal decreases as it travels through the air. Although Wi-Fi signals travel much better through the air than through solid materials they will still lose power over time, resulting in interference at the signal's destination. The best way to avoid attenuation due to range is to keep your wireless devices within 30 feet or so of your router.