I hooked up the ESP to my Spectrum Analyzer this morning.
Sorry for the Cellphone Pics , but I couldn't find a CF Card for the SA
Thats the ESP running at Wifi Channel 6 (2437MHz) , connected to my AP (~50cm away)
For comparison here is the same setup but with the ESP unpowered , my AP @ Ch6 is still quite visible.
Quite a lot of spurs from the ESP and the occupied BW is also not that good.
So anyone considering using the ESP in a commercial setup should think, imho, a bit about using an external bandpass filter ... and good luck for the FCC approval