Comment by gc22browsing

The problem at the radio frequency level is simply that not only is the 2.4GHz ISM band crowded by microwave ovens, WiFi and lots of other devices, but that one end of a BT device is typically battery powered and transmitting at a tiny fraction of the power of the interfering devices. In a typical office or home the moment you turn on the microwave or WiFi device you are effectively jamming the BT signal. Frequency hopping can hop it all likes and try to pick the least worse band out of all even more over-powering ones.