DISCLAMER/WARNING! HIGH VOLTAGE! HIGH POWER MICROWAVE RADIATION! USING THIS DEVICE MAY BE DANGEROUS TO YOU OR SOMEBODY NEARBY. IT CAN DESTROY EQUIPMENT, CAN CAUSE FIRE. HIGH VOLTAGE IS USED IN THIS DEVICE. ONLY EXPERIENCED PERSONEL CAN USE, BUILD SUCH DEVICES. ALMOST IN ALL COUNTRIES IT IS ILLEGAL TO BUILD NOT SERTIFIED RADIO TRANSMITTER. THIS DEVICES POWER OUTPUT IS FROM 300W TO 1KW. FREQUENCY OF THIS DEVICE IS ABOUT 2450MHz, BUT OTHER FREQUENCES ARE DETECTED TOO. READ THIS BEFORE! THIS DESCRIPTION IS FOR INFORMATION PURPOSES ONLY. SAVEL IS NOT RESPONSABLE FOR ANY DAMAGES TO EQUIPMENT AND HEALTH, AIR TRAFFIC PROBLEMS, GSM NETWORK FAILURES AND FALLING SATTELITES.

So, let's build something very crazy. In fact, you don't need to build anything! It is microwave oven. It happened, that I get bad microwave oven. After I breaked it into parts and throw away chassis, I managed to fix it. So, what we can do with high voltage transformer, magnetron, diode and big capacitor... Microwave gun! It is very sorry, but this device is not mobile. It consumes about 1kW of power, I don't know good batteries for such power.
Why we need microwave gun? For few interesting experiments. Like killing cocroaches and computers, some nice lightning effects.
How microwave gun/ microwave oven works? Main thing in this device is special lamp, called magnetron (I used 2M231H by Toshiba, 500W Microwave output). Why magnetron? Because this lamp has 2 big and powerfull magnets put on it. We need few volts to heat this lamp and few thousand volts for generation. Every oven has big transformer producing 3.5V for heating and few thousand volts output for the lamp. Electronic lamp need DC so one diode and capacitor is used for it. I don't have equipment to measure voltage, but it is much more than 1000V. (According to Toshiba manuals, it must be 3.5kV, 200mA DC)

Here is the schematics:

Magnetrom lamp must be cooled by forced air flow. For a few seconds radiation, coolling can be avoided. For heavy loads and long radiation you can use watter cooling.
Place magnetron to some metal box- it will be your microwave chamber. Don't use open microwave chamber. If you want to see some fireworks use some metal net. Something like one used on microwave oven door. Microwave radiation can't kill you in few seconds, but it can be dangerous especially for a long exposures. You can use metal foil for sealing holes. Sometimes sparks can make holes in foil- it is normal. It means that somewhere is bad sealing and high voltage is making current paths in the air. These sparks are very hot and simply melts the foil.

Unconnected "tube" lamp in MW Just simple "tube" lamp used in many cases. The light is produced by special white coating inside the tube. When lamp is working the current flows inside the tube with the help of mercury wapors and some inert gas. This mixture produces ultra violet radiation. UV rays reacts with special coating on tube. (Click on image for bigger photo).
Small Neon lamp in MW This is small lamp used in older devices for some indicating purposes. The light is produced when current goes threw neon gas inside the lamp. Net is used for safety
Simple ligh bulb in MW Simple light bulb. The light is produced from very hot tungsten wire. In MW case the light is produced in part from this wire and in part of argon gas used in every lamp. (Yes, every simple lamp has gas inside, not vacuum). Note the net used for safety and for power.