Microwave 'pitch' higher pitch means ...

[rotuts]

I have the standard over the stove built-in microwave. probably GE

from time to time on longer wavings the pitch of the oven goes up a little for a brief period of time.

this is generally when the oven inside is warm.

is this some sort of 'cut-off' so the microwave element itself does not get too hot? and just the fan cools it for 10 - 15 secs?

we are talking of wavings of 10 min or so +

thanks!

Edited December 4, 2011 by rotuts (log)

[qrn]

I think you are hearing the cooling fans for the thing.there are a lot of electronic things in there, and the cooling fan is probably a variable speed, depending on how hot stuff gets...

Bud

[pyrguy]

Most ovens cycle the tube on and off to regulate the power level. That is probably what you are hearing.

[dcarch]

I am with pyrguy.

Typically the cooling fan is a shaded pole motor, which is constant speed.

The magnetron tube operates only on or off, the power output therefore is FM (Frequency Modulated) not AM (Amplitude Modulated)

dcarch

Edited December 6, 2011 by dcarch (log)