4 ms·

You're correct that other frequencies would work, but have the causality backward when it comes to 2.4-2.5 GHz being a garbage dump. The nascent microwave oven

You're correct that other frequencies would work, but have the causality backward when it comes to 2.4-2.5 GHz being a garbage dump. The nascent microwave oven industry was making it into a de facto garbage dump, so the FCC requested that the ITU assign it as an official garbage dump. In other words, the ovens weren't put there because it was a garbage dump, it became a garbage dump because they were already there.

CamperBob2 3y ago
Yeah, good point there. Few licensed services probably wanted to co-exist with the RF leakage from a microwave oven. I imagine that 2.45 GHz was chosen as a compromise between cavity size/cost and food-penetrating power, but I don't think I've seen a definitive historical answer. The sweet spot for cooking effectiveness might even be at a somewhat-higher frequency, but it would have been more expensive to build ovens at higher frequencies back in the day, and it would also be more expensive to shield them properly. Like the GP suggests, at lower frequencies the size of the whole thing starts to become a problem for household use.
- jhoechtl 3y ago
  No, the dimensions of the magnetron changes and the mesh size at the door, otherwise it's just the same. Penetration depth at higher frequencies is lower, a lower resonant frequency penetrating deeper the tissue while engaging water molecules would be better
- Turing_Machine 3y ago
  This is pure speculation, but I wonder if it might also have something to do with surplus cavity magnetrons (and the production facilities for them) becoming available post-WWII. I can't find anything definitive on production models, but I was able to determine that the prototype magnetron that Churchill sent to the United States in secret operated at around 3 GHz...pretty close. Maybe cheaper to use the ones that already had production lines set up, if they were otherwise workable?
dtgriscom 3y ago
https://en.wikipedia.org/wiki/Peryton https://en.wikipedia.org/wiki/Peryton

CamperBob2 3y ago

Yeah, good point there. Few licensed services probably wanted to co-exist with the RF leakage from a microwave oven. I imagine that 2.45 GHz was chosen as a compromise between cavity size/cost and food-penetrating power, but I don't think I've seen a definitive historical answer. The sweet spot for cooking effectiveness might even be at a somewhat-higher frequency, but it would have been more expensive to build ovens at higher frequencies back in the day, and it would also be more expensive to shield them properly. Like the GP suggests, at lower frequencies the size of the whole thing starts to become a problem for household use.

jhoechtl 3y ago
No, the dimensions of the magnetron changes and the mesh size at the door, otherwise it's just the same. Penetration depth at higher frequencies is lower, a lower resonant frequency penetrating deeper the tissue while engaging water molecules would be better
Turing_Machine 3y ago
This is pure speculation, but I wonder if it might also have something to do with surplus cavity magnetrons (and the production facilities for them) becoming available post-WWII. I can't find anything definitive on production models, but I was able to determine that the prototype magnetron that Churchill sent to the United States in secret operated at around 3 GHz...pretty close. Maybe cheaper to use the ones that already had production lines set up, if they were otherwise workable?

dtgriscom 3y ago

https://en.wikipedia.org/wiki/Peryton https://en.wikipedia.org/wiki/Peryton