ORIGINAL: Missileman
I should have said harmonics, Bruce is right. I know some of the theory but I really don't understand it well enough.
In practice I have only had a 2.4 Ghz radio interefered with once and that was from a 2.4 Ghz cordless phone of all things almost cost me a helicopter.
This is actually a very legitimate source for 2.4 Ghz interference. There are a BUNCH of devices that are not RC related that operate in the 2.4 Ghz frequency ranges. Some that jump immediately to mind are computer wireless communications (Wi-Fi), telephones, video equipment, high speed data transmission equipment, as well as many more not mentioned. Most of the devices that are computer related are "Spread Spectrum" certified which means that they will "work and play well" with other Spread Spectrum devices. Our radios fall into that category. But for those devices that don't fall into that category they can and WILL interfere with our radios. I know this one for a fact. I build and manage computer networks for a living. I have some long range (up to 45 miles) wireless networking equipment that operates on 2.4 Ghz. This equipment broadcasts on a very narrow band when it's mounted on a tower, but if this were beamed across an area where a flying field was located it is possible that it could interfere with an RC radio.
Some items like telephones and video equipment have already proven to be able to interfere with our radios.
Ken