any one plesae has an idea about the following question related to microwave oven 1-does a microwave excite a signal mode or multiple mode, and why is this prefered? 2-explain mode stirring and how it is implemented in microwave ovens???? note that the microwave oven excited at 25 GHZ
microwave oven
Started by ●April 16, 2008
Reply by ●April 17, 20082008-04-17
On Apr 16, 6:54�pm, ahmed_...@hotmail.com wrote:> any one plesae has an idea about the following question related to > microwave oven > > 1-does a microwave excite a signal mode or multiple mode, and why is > this prefered? > > 2-explain mode stirring and how it is implemented in microwave > ovens???? > > note that the microwave oven excited at 25 GHZYour professor has idea.
Reply by ●April 17, 20082008-04-17
ahmed_hus@hotmail.com wrote:> any one plesae has an idea about the following question related to > microwave oven > > > 1-does a microwave excite a signal mode or multiple mode, and why is > this prefered? > > > 2-explain mode stirring and how it is implemented in microwave > ovens???? > > note that the microwave oven excited at 25 GHZThe questions are intended to probe your knowledge. Getting others to answer them does nobody any good. Read more carefully: you misread "single" as signal. Not at all the same thing. What is a mode? What determines the modes that can exist in a cavity? You will probably be able to answer the professor's question when you can answer mine. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●April 17, 20082008-04-17
On Apr 17, 11:54�am, Jerry Avins <j...@ieee.org> wrote:> ahmed_...@hotmail.com wrote: > > any one plesae has an idea about the following question related to > > microwave oven > > > 1-does a microwave excite a signal mode or multiple mode, and why is > > this prefered? > > > 2-explain mode stirring and how it is implemented in microwave > > ovens???? > > > note that the microwave oven excited at 25 GHZ > > The questions are intended to probe your knowledge. Getting others to > answer them does nobody any good. Read more carefully: you misread > "single" as signal. Not at all the same thing. > > What is a mode? What determines the modes that can exist in a cavity? > You will probably be able to answer the professor's question when you > can answer mine. > > Jerry > -- > Engineering is the art of making what you want from things you can get. > �����������������������������������������������������������������������To the op.. I'll offer you one more bit of help.. you either have a typo or a misunderstanding of one key word in the question... the correct question #1 should be: does a microwave excite a SINGLE (not signal) mode or multiple modeS, and why is this prefered? Mark
Reply by ●April 17, 20082008-04-17
On Apr 17, 2:12�pm, Mark <makol...@yahoo.com> wrote:> On Apr 17, 11:54�am, Jerry Avins <j...@ieee.org> wrote: > > > > > ahmed_...@hotmail.com wrote: > > > any one plesae has an idea about the following question related to > > > microwave oven > > > > 1-does a microwave excite a signal mode or multiple mode, and why is > > > this prefered? > > > > 2-explain mode stirring and how it is implemented in microwave > > > ovens???? > > > > note that the microwave oven excited at 25 GHZ > > > The questions are intended to probe your knowledge. Getting others to > > answer them does nobody any good. Read more carefully: you misread > > "single" as signal. Not at all the same thing. > > > What is a mode? What determines the modes that can exist in a cavity? > > You will probably be able to answer the professor's question when you > > can answer mine. > > > Jerry > > -- > > Engineering is the art of making what you want from things you can get. > > ����������������������������������������������������������������������� > > To the op.. > > I'll offer you one more bit of help.. > you either have a typo or a misunderstanding of one key word in the > question... > > the correct question #1 �should be: > > does a microwave excite a SINGLE (not signal) �mode or multiple modeS, > and why is this prefered? > > Mark- Hide quoted text - > > - Show quoted text -my bad... I didn't read Jerry's post carefuly...sorry.. Mark
Reply by ●April 17, 20082008-04-17
Jerry Avins wrote:> ahmed_hus@hotmail.com wrote:(snip)>> 1-does a microwave excite a signal mode or multiple mode, and why is >> this prefered?>> 2-explain mode stirring and how it is implemented in microwave >> ovens????>> note that the microwave oven excited at 25 GHZ> The questions are intended to probe your knowledge. Getting others to > answer them does nobody any good. Read more carefully: you misread > "single" as signal. Not at all the same thing.> What is a mode? What determines the modes that can exist in a cavity? > You will probably be able to answer the professor's question when you > can answer mine.I believe that they don't do mode stirring anymore. When you find the actual answer for ones that did do mode stirring you will probably laugh. At least that is what I did when I first learned about it. Now, instead of stirring the modes they move the food. Not quite the same thing, but it takes up less space and makes people think they are getting more instead of less. Also, I believe it is a lot less than 25GHz unless they recently changed the frequency. (It has to be an absorption band for water.) -- glen
Reply by ●April 17, 20082008-04-17
On Thu, 17 Apr 2008 11:42:16 -0800, glen herrmannsfeldt <gah@ugcs.caltech.edu> wrote:>Jerry Avins wrote: > >> ahmed_hus@hotmail.com wrote: >(snip) > >>> 1-does a microwave excite a signal mode or multiple mode, and why is >>> this prefered? > >>> 2-explain mode stirring and how it is implemented in microwave >>> ovens???? > >>> note that the microwave oven excited at 25 GHZ > >> The questions are intended to probe your knowledge. Getting others to >> answer them does nobody any good. Read more carefully: you misread >> "single" as signal. Not at all the same thing. > >> What is a mode? What determines the modes that can exist in a cavity? >> You will probably be able to answer the professor's question when you >> can answer mine. > >I believe that they don't do mode stirring anymore. When you find >the actual answer for ones that did do mode stirring you will >probably laugh. At least that is what I did when I first learned >about it. Now, instead of stirring the modes they move the food. >Not quite the same thing, but it takes up less space and makes >people think they are getting more instead of less. > >Also, I believe it is a lot less than 25GHz unless they recently >changed the frequency. (It has to be an absorption band for >water.) > >-- glenHe may have meant 2.5GHz, although there may be microwave ovens that operate at 25GHz. I suspect they'd be pretty expensive if they do exist. Many of the big commercial microwave ovens (for factory applications like pre-cooking pre-packaged food) operate at 900MHz or thereabouts depending on regional regulations. Most consumer ovens operate at 2.4GHz, which is essentially unified globally as an unlicensed band for ISM-type equipment. Eric Jacobsen Minister of Algorithms Abineau Communications http://www.ericjacobsen.org
Reply by ●April 17, 20082008-04-17
glen herrmannsfeldt wrote:> Jerry Avins wrote: > >> ahmed_hus@hotmail.com wrote: > (snip) > >>> 1-does a microwave excite a signal mode or multiple mode, and why is >>> this prefered? > >>> 2-explain mode stirring and how it is implemented in microwave >>> ovens???? > >>> note that the microwave oven excited at 25 GHZ > >> The questions are intended to probe your knowledge. Getting others to >> answer them does nobody any good. Read more carefully: you misread >> "single" as signal. Not at all the same thing. > >> What is a mode? What determines the modes that can exist in a cavity? >> You will probably be able to answer the professor's question when you >> can answer mine. > > I believe that they don't do mode stirring anymore. When you find > the actual answer for ones that did do mode stirring you will > probably laugh. At least that is what I did when I first learned > about it. Now, instead of stirring the modes they move the food. > Not quite the same thing, but it takes up less space and makes > people think they are getting more instead of less.The mode stirrer on my now-defunct zapper was a sort of propeller moved by the cooling air leaving the magnetron. That is cheaper than a turntable.> Also, I believe it is a lot less than 25GHz unless they recently > changed the frequency. (It has to be an absorption band for > water.)If the frequency is at the absorption resonance, penetration is too shallow. As far as I know, the usual frequency is between the absorption peak of water and the absorption peak of typical fats, 2.45 Ghz. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by ●April 18, 20082008-04-18
glen herrmannsfeldt wrote:> I believe that they don't do mode stirring anymore. When you find > the actual answer for ones that did do mode stirring you will > probably laugh. At least that is what I did when I first learned > about it. Now, instead of stirring the modes they move the food. > Not quite the same thing, but it takes up less space and makes > people think they are getting more instead of less.Isn't it the other way around? In the stirring ovens, the food could fill the entire rectangular area. Now the food has to be rotatable, only filling the central circular area, so the whole oven has to be bigger.> Also, I believe it is a lot less than 25GHz unless they recently > changed the frequency. (It has to be an absorption band for > water.)If they can get the frequency high enough, the oven would become a conventional heater. :-) Regards, Steve
Reply by ●April 18, 20082008-04-18
Jerry Avins wrote: (snip)> The mode stirrer on my now-defunct zapper was a sort of propeller moved > by the cooling air leaving the magnetron. That is cheaper than a turntable.I thought the one I used to use had a motor to drive it, but it looks a lot like a slow moving fan. They might be cheaper than turntables, but they take up more room, and people don't see them. It is easier to advertise a feature that people can see, and ask why others don't have that feature. Turntables don't work as well with square dishes. -- glen
