OK - One can recycle an old microwave
oven into a pest and weed exterminating device. Take the microwave
oven apart and keep the magnetron, power supply, fan, light, and on/off switch. Using the sheet metal from the oven or a galvanized
stove pipe, mount the magnetron at the front with the microwave emitter centered and pointed out it should be set back from the end about six inches or so to
shroud the beam. Use the same holes that bolt the magnetron to the inside of the pipe to affix the forward hand grip probably made from wood. Mount the fan in back of the magnetron so that it will blow air over the power supply which is mounted at the back. Use the bolts that secure the power supply to mount the rear hand grip this hand grip is hollow and the power cord* runs out of the handle to
plug into an extension cord. The hand grip also mounts the trigger type on/off switch which will only stay on while it is being held back with the trigger finger. Mount the oven light** over the power supply and change to a red bulb if possible (to let the user know the unit is on, and to protect night vision). Use some metal screening material, perhaps that found in the oven door, to
screen the rear opening of the pipe. As an option, one might affix an old laser pointer** to the top of the magnetron, run by the power supply, to show where the invisible microwave beam is being directed.
* For portable use perhaps on a
boat one could power the unit for a limited amount of time using a small twelve volt motorcycle
battery and an appropriately sized
inverter.
** To save power and up the visibility, dispense with the small oven light and instead of a laser pointer, use an array of four write heads from an old recycled CD/DVD burner.
Cheap but powerful, this would outline the invisible microwave beam with four red dots. Note that the laser array is likely powerful enough to cause temporary blindness if directed into someones eyes. The trigger could be wired so that as the trigger is pulled back the laser array comes on, continue pulling and the microwave beam comes on.
When on, the magnetron will emit a compact stream of microwave energy this should be tested by aiming the device at a small glass of
water. One should be able to get a feel for the direction and range of the microwave beam by noting how long it takes the
water to boil. In general, microwave energy is not good for living things as it excites the water found therein which heats the item up. An insect, perhaps a cockroach, is a small quantity of mostly water contained in a chitin shell and this small quantity of water can be rapidly heated to over the temperature at which insects die (around 105 F). A similar thing happens to the leaves of plants (weeds). Microwaves will go through some stuff like plastic, wood, concrete, and earth (like ground penetrating
radar does) so for
safety you should know what is on the other side of walls and this feature might be used to kill pests inside the walls (cockroaches, mice, etc). Some experimentation will be needed to determine the range and penetration of your unit. Microwaves do NOT penetrate metal, so any metal surface in the beam will act like a mirror and reflect the microwave beam if the surface is flat the beam will be reflected at an angle (the angle of reflection is equal to the angle of incidence), if the surface is convex the beam will be dissipated, but if the surface is concave the beam may become concentrated (at least for some distance). Some prudence is indicated here.
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