Excellent post. You are right about the scaling. Having worked with the researcher, I believe that I can say that they believe that it will scale quite easily.
Mod this up. This is right. The frequency of the microwave oven doesn't matter. Water will absorb 1, 3, or 20 GHz just as easily. If I were to take a guess why they chose 2.45 GHz, I would say size. The lower the frequency, the larger your magnetron. The higher frequency, the smaller the magnetron. The s-band magnetron is pretty small. Easy to make and fit in a microwave oven. And X-band microwave is probably too small and would cost to much to make. The L-band magnetron is monstrous.
I disagree. If this were something that had been done with radar, then someone would have done it to magnetrons 20 years ago and we would have no noisy magnetron problems. The fact of the matter is that the scientific community has been working on this noise problem for decades. It was always thought that a axial magnetic field with no azimuthal variation was needed to minimize noise. Untrue. These researchers, whom I personally know, have found that the azimuthal variation reduces the noise. The pattern is not specific to the waveguide and couplings. It is dependent only on the magnetron, which contrary to your thought, is actually built to modest quality standards. These things output up to 90% efficiency at 2.45GHz. That is a tall order. The manufacturers do a pretty good job. They just need to start using this technique. And yes, I AM an expert on the subject and have personal experience with this technique.
Up until four days ago, I was a graduate student in this laboratory. (Just graduated!) Here are some other links with more information, but the above PDF is probably the most detailed, being a journal article.
Research projects currently underway by the same U of Michigan group. Some cool stuff. Check it out. The microwave noise project is the first link. Nice PIC of the setup. Also a couple audio files showing the noise interference to a cordless phone before and after the modification.
But, if I can sue FooBar Company for registering typos that closely resemble my trademark, can't I sue Verisign for using typos that closely resemble my trademark? I don't see much of a difference here. I think that Verisign's actions open it up to an enormous number of lawsuits from the biggest companies in the world.
I wish/. had a full-time lawyer to read over this stuff and offer her opinion, that would be cool.
This is a great idea. Any lawyers out there who want to become Slashdot's Voluntary Legal Opinion Provider? I'm sure you'd get tons of business from rankled posters.
I wouldn't bet on 90% efficiency. Not by a long shot. My dissertation is on magnetrons. I can tell you from experience that if these guys want to maintain high efficiency, they have to use a magnetron. It is the most efficient RF tube there is. We have measured efficiencies on 2.45GHz magnetrons to be as much as 85%. That is a 1 kW oven. If you start moving up in powers you either lose efficiency (dropping to 30% or lower at relativistic voltages) or you have to add magnetrons to the system to get your powers up to something respectable.
Assuming you could get 10 MW or so at 90% efficiency, you then have all the other steps to consider. You mentioned that the rectennas are able to convert 90% of the RF back to DC. I'd like to see the journal article. That sounds pretty amazing if it is true. But even if it is true, if you only take the Rectenna and magnetron into consideration, your efficiency is no where near 90%.
Then we move to the idea that you're beaming large amounts of 2.45 GHz radiation. Maybe the mW radiating from your phone and 802.11b router aren't a lot, but the quantities needed to generate DC power can cook a turkey. I wouldn't want to be the turkey anywhere near the path of that beam. I don't care how well it is aimed to a collecting rectenna.
Why is the parent to this thread modded up to +5, Insightful? I don't think so. Maybe a +3 for the first paragraph, but -1, Troll for that last bit of flamebait about the Bush/Clinton/Gore thing.
Big companies have been fighting state taxation tooth and nail. States have been the ones pushing for it.
This is no joke. I work as a graduate student research assistant in engineering. Industry types are always telling us that they need more experimentalists. There is a big shortage of experimentalists right now. If you know how to build and run an experiment, you're golden.
Slashdot Mirror
Excellent post. You are right about the scaling. Having worked with the researcher, I believe that I can say that they believe that it will scale quite easily.
Mod this up. This is right. The frequency of the microwave oven doesn't matter. Water will absorb 1, 3, or 20 GHz just as easily. If I were to take a guess why they chose 2.45 GHz, I would say size. The lower the frequency, the larger your magnetron. The higher frequency, the smaller the magnetron. The s-band magnetron is pretty small. Easy to make and fit in a microwave oven. And X-band microwave is probably too small and would cost to much to make. The L-band magnetron is monstrous.
I disagree. If this were something that had been done with radar, then someone would have done it to magnetrons 20 years ago and we would have no noisy magnetron problems. The fact of the matter is that the scientific community has been working on this noise problem for decades. It was always thought that a axial magnetic field with no azimuthal variation was needed to minimize noise. Untrue. These researchers, whom I personally know, have found that the azimuthal variation reduces the noise. The pattern is not specific to the waveguide and couplings. It is dependent only on the magnetron, which contrary to your thought, is actually built to modest quality standards. These things output up to 90% efficiency at 2.45GHz. That is a tall order. The manufacturers do a pretty good job. They just need to start using this technique. And yes, I AM an expert on the subject and have personal experience with this technique.
Press release after a recent APS conference
Extended summary of research (PDF) and
Research projects currently underway by the same U of Michigan group. Some cool stuff. Check it out. The microwave noise project is the first link. Nice PIC of the setup. Also a couple audio files showing the noise interference to a cordless phone before and after the modification.
But, if I can sue FooBar Company for registering typos that closely resemble my trademark, can't I sue Verisign for using typos that closely resemble my trademark? I don't see much of a difference here. I think that Verisign's actions open it up to an enormous number of lawsuits from the biggest companies in the world.
This is a great idea. Any lawyers out there who want to become Slashdot's Voluntary Legal Opinion Provider? I'm sure you'd get tons of business from rankled posters.
Thanks for the journal article. I'll definitely have to check this out.
Assuming you could get 10 MW or so at 90% efficiency, you then have all the other steps to consider. You mentioned that the rectennas are able to convert 90% of the RF back to DC. I'd like to see the journal article. That sounds pretty amazing if it is true. But even if it is true, if you only take the Rectenna and magnetron into consideration, your efficiency is no where near 90%.
Then we move to the idea that you're beaming large amounts of 2.45 GHz radiation. Maybe the mW radiating from your phone and 802.11b router aren't a lot, but the quantities needed to generate DC power can cook a turkey. I wouldn't want to be the turkey anywhere near the path of that beam. I don't care how well it is aimed to a collecting rectenna.
I'm sorry, I've already filed a patent for "Method of tracking state taxes charged through internet electronic sales kiosks."
Why is the parent to this thread modded up to +5, Insightful? I don't think so. Maybe a +3 for the first paragraph, but -1, Troll for that last bit of flamebait about the Bush/Clinton/Gore thing.
Big companies have been fighting state taxation tooth and nail. States have been the ones pushing for it.
This is no joke. I work as a graduate student research assistant in engineering. Industry types are always telling us that they need more experimentalists. There is a big shortage of experimentalists right now. If you know how to build and run an experiment, you're golden.