As a newcomer to this newsgroup, please allow me to clarify.

I do not mean to dispute your information about the stirrer blades, I
agree with you.

I am trying to get more information about what exactly is involved in
the dispersion. More than what I pick up off of the various "how does a
microwave oven work" hits that google returns.

Thank you,

Mike K.

g They are in the path between the magetron and the oven (cavity).
The microwaves reflect off the blades at varying angles (as the blades
turn).

It (the cooking chamber) is not a resonant cavity. To be that it would
have to be rather small (a wavelength of a microwave oven is in the
range of 4 to 5 inches, IIRC). There are 'hot' spots (and cool spots)
in that chamber, caused by reflections, and the interface between the
source and the oven chamber.

I hope you don't mind the discussion. And I hope you don't mind that I
address your points out of sequence.

I think you are close enough in wavelength for our discussion. But you
can set up a standing wave of half a wavelength, which would be
approximately the size of the standard cooking chamber of the average
microwave oven.

I note that there is not a large variation in microwave oven sizes.
Perhaps cooking a large turkey would be impractical due to overcooking
at the surface, but I can envision a scenario where you might want to
heat up 20 bowls of soup at a time.

I don't see this happening, that is why I think that the cooking
chamber size is dependent on the wavelength being used. And since the
wavelength of the microwave is limited by the economic considerations
of the magnetron, this restricts the range of the cooking chamber.

This is why if you have a turntable microwave without a dispersal fan
and take out the turntable (or it breaks... g) you can end up with
your dinner over cooked in some places and frozen in other spots.

I used a microwave resonance system and we turned the cavity by making
adjustments at the boundary layer between the wave guide and cavity. It
seemed to me that the dispersal fan might be method of tuning the
cavity through the various modes of the cavity, averaging out the maxs
and mins of the standing wave.

-Mike K.