As we all know, microwaves can heat things. Microwaves could also be used in theory to heat people and objects or damage sensitive electronic devices. A standard microwave oven is a good source of components for this task. I have tried inserting a magnetron into a satellite dish with no real success, It is rated for 650 watts and will light a fluorescent tube from a meter away and burn PCB’s at a distance of one inch. Standing near it barely induces a sensation of heat although placing a hand near the antenna is unpleasant (think putting your hand near a fire). The US government have developed such a system called the “Active Denial System” or “ADS”. From memory it works at 95 GHz.
Replacing the LNBF with a magnetron increases range especially coupled with the wave guide from the microwave oven the magnetron was removed from. It will also interfere with electronic devices from a distance. It upsets the stereo in my workshop when it is in operation by scatter of microwaves off of the walls alone. Turning it off then back on restores normal operation although a direct hit would likely kill it. One could in theory damage things like CCTV or other electronic devices or just interfere with them. That or jam wifi or other services on the 2.4 GHz band.
An interesting discovery from this is what is referred to as the “Frey Effect”. Basically it is a result of the pulsating heating of the structure of the ear which creates sound. Basically it is a humming sound what appears to be coming from inside your head but is caused by exposure to the microwave beam. You could theoretically modulate the magnetron with audio and insert voices into a targeted person’s head. A US army research team tried this in 2003 as a form of deterrent around secure areas. The sound would seem uncomfortably loud to any one targeted by the system . It could also be used to harass certain people or cause them to think they are mentally ill in some way. The possibilities are endless. Frequencies between 200 MHz and 3 GHz tend to produce this effect at a minimum of around 80 mW/cm2.