How do flatbed microwave ovens work?

This is what I think of as a magnetron, as used in conventional microwave ovens with a turntable: http://www.hokuto.co.jp/eng/products/magnetron/img/index_img_01.gif
It's about the size of a fist. So how do they make them flat under the food cavity in flatbed ovens? Does the magnetron sit under there and is redesigned to be flat? Or is there some kind of fancy rotating waveguide, and the magnetron sits at the side as before?

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Basically the later I should think.
The one I had in the 1980s had a large aperture covered with mica on the roof of the cooking cavity. The Magnetron was at the side of the cavity with a brass wave guide leading up to the top. A squirrel-cage fan blows air up the wave guide and not only cools the Magnetron, but also rotates a paddle-wheel at the top, a rotating antenna, carrying multiple reflectors thar distribute the radiation throughout the cavity. I imagine modern bottom entry ones do a similar trick, but I have yet to work on one.

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I didn't realise they were available in 1980. So why aren't they all like that? Does it add a lot to the price?

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The one we had is in the last illustration on this page
https://www.photomemorabilia.co.uk/Photopia/Plustronics_Literature.html
I've still got the 170 page hard-back cookery book.

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Bloody hell, those look like very well made and very expensive(?) products.

On 01/06/2018 18:13, Graham. wrote:
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That looks quite a sophisticated one for the early 80s. We bought one around 1981 and it had just a simple turn and 'run back' timer. It did last about 17 years, with only a couple of O rings in the turn table drive. We only disposed of it as it started to look tatty.
We've had several since, none have lasted so well.

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I once had a microwave that decided to run continuously for no reason, I think some water got through into the workings underneath. Maybe it was just the motor, but I couldn't be bothered as it was a cheap oven so I threw it out. I should have had a look inside.

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I'm still using the Sharp I bought in 73 almost every day.
It does have a proper electronic control and display.
Never had to do a thing to it.
Corse now it will curl up and die and it will be your fault.
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Whatever happened to Sharp, they still seem to be in business, but I haven't seen anything made by them for a decade or two.

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Nothing special here.
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Yep.
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They arent as cheap as the worst crap but still buyable here. https://www.sharp.net.au/

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Maybe here too, but I just haven't seen anyone with a Sharp device for 20 years. They used to be everywhere. AFAIK they were always midrange. Not overpriced like Sony, but decent. Something like LG.
Just checked a retailer here: https://www.currys.co.uk/gbuk/household-appliances/cooking/microwaves/335_3152_32014_xx_xx/xx-criteria.html 5 Sharp microwaves on offer, but 40 Russell Hobbs, 29 Bosch, 24 Swan, 15 Samsung, 25 Hotpoint. So not the most popular by far.

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There's heaps here https://www.sharp.net.au/home-products/microwaves

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I recall a Phillips one in the 70's which had the controls and presumably the magnetron above the cavity. I don't think it had a turntable. One would suit me now as it woual be narrower.
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I wonder if it rotated? How unevenly cooked would something be without rotation? Would conduction of heat make up for it? I guess somebody could try it by removing the turntable from a conventional microwave.

I recall a Phillips one in the 70's which had the controls and presumably the magnetron above the cavity. I don't think it had a turntable. One would suit me now as it woual be narrower.
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Yes, but how common are they compared to other makes?