2.4 GHZ signals
Stop the interference! - Network World
Microwave ovens are No. 1. They provide a pulse form of inference and typically hammer the middle of the Wi-Fi 2.4 GHz band. When they send their pulses, the majority of consumer ovens occupy 802.11 b/g channels 5, 6 and 7, but they may start their pulse on channels 1 or 11.
The second biggest interference comes from older continuous wave frequency modulated cordless phones. These are not the more recent frequency hopping variety. These continuous wave cordless phones typically occupy channels 0 through 2.Fourth on the list are Direct Sequence Spread Spectrum (DSSS) and Orthogonal Frequency Division Multiplexing (OFDM) cordless phones. These phones are in both 2.4 GHz and 5 GHz spectrums, and are a little nicer because both 802.11b/g and 802.11a access points can recognize the traffic and treat it somewhat like another Wi-Fi device. The catch? When these phones are handling a call, you can lose half of your bandwidth for the duration of the call. If you have multiple handsets on a single base station, though, the second remote handset will permanently cut your Wi-Fi bandwidth in half.