"Pete C." > wrote in message
ter.com...

>
> Ok, here goes:
>
> Microwave ovens heat food by exposing it to microwave (radio frequency)
> radiation which causes the food molecules to vibrate causing friction
> and generating heat.
>
> Microwave radiation is generated by a magnetron and travels in a
> relatively straight beam from the magnetron's output port. This beam of
> microwave radiation bounces off the walls of the oven cavity until it
> hits and is absorbed by the food.
>
> Since the microwave radiation travels in a relatively straight beam, it
> will tend to setup a standing wave pattern of reflections inside the
> oven cavity which can leave areas of food relatively untouched by the
> beam and thus unheated and uncooked.
>
> There are two main techniques used to overcome this issue, turntables
> for the food and stirrers for the microwave beam. Turntables are pretty
> obvious and work by rotating the food through the microwave standing
> wave pattern and thus heating the food more evenly.
>
> Stirrers are less obvious since they are usually hidden, but basically
> they are a metal fan blade of sorts that spins at a fairly slow speed
> and is placed in the path of the microwave beam exiting the magnetron
> and are usually behind the microwave exit port (a fiberglass panel of
> sorts) so they aren't visible.
>
> By spinning in the path of the microwave beam, the stirrer deflects the
> beam at a wide range of angles on it's way into the oven cavity thereby
> eliminating standing wave patterns and ensuring even coverage of the
> food.
>

Makes perfect sense now! Thank you! So those with just a turntable and not
a paddle or deflector probably shouldn't be used without the turntable
spinning. I'm looking to replace my very very old microwave oven, soon,
too, so I'm reading this with a lot of interest. Same with the dishwasher
thread.

My old microwave oven has a visible fan in the top of the unit behind the
"ceiling" of the unit but has little holes, that I never really gave much
thought.