Microwave oven interfering with WiFi on the 2.4GHz band
As I understand it, microwave oven magnetrons operate at 2.45GHz, which is an unlicensed band in most of the world. When 2.4GHz technologies such as WiFi (802.11), Bluetooth and Zigbee were launched, there were concerns that these would collide with microwave oven frequences. I remember a very early (year 2000-ish) Bluetooth evaluation project where I amused myself by placing two Bluetooth modules on each side of a running microwave oven and couldn't get any form of Bluetooth traffic working.
But are microwave ovens really allowed to cause interference at longer distances, such as jamming out WiFi located in the same room or building? My take is that they should count as non-specific SRD (short range device). I'm located in Europe, so in that case the 2400-2450MHz unlicenced, harmonised band should apply - this is standardized by the European Radiocommunications Committee within the whole of EU. If so the SRD standard EN/ETSI 300 440 for non-specific SRD (sorting under the new RED directive) should apply. Is this correct so far? Or do microwave ovens have their own specific technical standard?
ETSI standards are conveniently available for free, so I checked v.2.1.1 of EN/ETSI 300 440. Chapter 22.214.171.124 regarding limits of unwanted emissions in the spurious domain are limited to 1uW for frequencies > 1 GHz. I'm assuming this is 1uW E.R.P, so roughly -30dBm E.R.P. The spurious domain is defined in complex ways by this standard depending on bandwidth from carrier. I don't think a device that disturbs with -30dBm E.R.P. would affect WiFi or any other radio technology much at all. Or would it? Would the "listen before talk" RSSI limit of WiFi cause any problems here?
Could any radiated emission from a microwave be regarded as an intentional radiator? Does it have a designated carrier and occupied band, where it may act just as any other SRD? I'm assuming that the microwave oven occupied band is very wide, several 100MHz.
If so, then what happens when the microwave occupied band (+/- x MHz from carrier) collides with the WiFi occupied band? There are a couple of (European) WiFi channels that overlap with 2.45GHz specifically. Since WiFi (and Bluetooth) use spread spectrum technologies, would that mean that WiFi skips certain channels, resulting in reduced bandwidth?