Electromagnetic superposition is, by definition, interferrence.
Please don't take me wrong. I think we are in agreement, but I was merely drawing a distinction between the first definition and the fifth as illustrated below (courtesy Merrriam-Webster Online).
interference n. 2 : the mutual effect on meeting of two wave trains (as of light or sound) that constitutes alternating areas of increased and decreased amplitude (as light and dark lines or louder and softer sound) 5 a : confusion of a received radio signal due to the presence of noise (as atmospherics) or signals from two or more transmitters on a single frequency.
The point I was trying to make (and the point I think Reed was making) is that with the right type of receiver, you can recuce or eliminate such interference. Hence his statement that the interference is a limitation of the receiving device.
But Reed isn't using "interferrence" in this technical sense. He just means...
Actually, I think Reed was using interference in exactly the sense that I'm talking about and, as you pointed out, ignores many of the real world implications of actually implementing the devices he's promoting.
In your crowded room analogy you can't hear what's being said because your ears hear in all directions (A limitation of the receiving equipment as Reed puts it). If your ears were directional like your eyes, you could eliminate virtually all the sound interference and could selectively listen to different people in the room (just as the people using sign language are able to because there eyes are direcional).
He's basically saying that using currenly common tv/radio antennas is like viewing the world with cataracts. (My analogy)
One possible exception is polarization multiplexing...
...or spatial seperation. Please note that any two distinct broadcasts on the same frequence must be broadcasting from different locations. Phased array antennas are designed to take advantage of that to selectively choose the signal. As these systems get better and better, we get closer and closer to the possibilities that this article talks about.
Nothing which Reed presents allows him to circumvent the Shannon limit...
If you have an antenna that can selectively choose a source based on direction/polarization, then that source could use the full spectrum (ie. no fixed bandwidth) and the Shannon limit is irrelevant.;)
People, PLEASE do some reading about phased array antennas before you go and shoot your mouths off.
These are dirrectional antennas that are able to do spatial seperation of signals electronically using signal processing (ie. without moving the antenna). They can also broadcast in any particular direction using the same phasing techniques.
They've already been around for quite a while (eg. NORAD) and with DSPs becoming so inexpensive a lot of work is being done on getting them into the private sector.
As I've said before, what some call 'radio interference', a physicist would call electromagnetic superposition. If there are ways to distinguish the signals via spatially or polarizationally sensitive antennas, then this so-called 'interference' can be eliminated.
While the article was extremely light on technical discussion, his points are entirely valid. Just what do you think 'interferance' is anyway?
What a communications engineer calls "radio interferance", a physicist would call electromagnetic superposition.
If you have an antenna that can't seperate out the superimposed signals, you get 'interferance'. While common radio and tv antenna's can't seperate these signals, other types of directional or polarization sensitive antennas can seperate out these signals so there is no interferance.
A lot of work has been and is currently being done on antennas where this can be all done electronically (ie. you don't have to reposition as you do with conventional directional antennas).
For more information, go do some reading on DSP controlled phased array antennas.;)
Let me guess... English is your second language?... third? His argument is perfectly correct. Maybe you misunderstood it.
His point was that our eyes DO seperate out spatially distinct signals. Common radio/TV antennas DON'T.
What people refer to as "radio interferance" is really just EM superposition and could be removed with an antenna that can sererate spatially distinct signals.
Sorry, but unless a body's at absolute zero, it DOES radiate light in the same way as the sun... by black body radiation. Just 'cause you can't see it...
Now if you want to say that the wavelength of the most intensely radiated light is less than 700nm...;)
Also, most people consider another defining characteristic of planets, which is ignored entirely by the above definition, to be that they're gravitationally bound to other objects.
Planet: n. Any object orbiting a star, not orbiting a planet, and having a radius greater than the radius of Pluto minus one millimeter.
Great! You've just classified virtually all minor stars in binary systems as planets!;)
Personally I think we should keep the definition of planet as any non-stellar object orbiting a star. We should just add classes for features such as surface gravity, atmosphere orbital eccentricity, maybe even surface temperature.
An asteroid might be a class P planetoid. Jupiter might be class G3, or earth might be an M class planet.;)
Then we'd be here arguing over just "How much atmosphere constitutes an atmosphere?", and to settle disputes, we'd need to use the Uniform Planetary-Class Dispute-Resolution Policy.;)
I was watching some 'scientists' dating a glacier flow on a PBS documentary. Since there was no organic matter, they took pieces of rock that had been torn off by the glacier and used radiometric dating on the rocks. They claimed that that was the age of the when the glacier had broken the rock away.
HELLO??? I know that there isn't a lot of cross over between geology and biology, but OUCH!!!
Now if they had tried to guess the age of the fractured surface of the rock using some kind of oxidation rate or something, they might have been ballparkish. At the time, I just couldn't believe that any scientists could be that stupid. Of course now I know better.:)
You even have to be careful of experiments in quantum physics in refereed journals these days. Fields are highly specialized and sometimes explainations that would be obvious to some are overlooked by those writing the papers. You end up with all kinds of contradictions. Did you realize that treating the simultaneous collapse of a quantum wave function of entangled particles as a physical event is entirely inconsistent with the tenets of special relativity? Something's gotta give.;)
Water vapour stays frozen out of the atmosphere until you reach, well, 0 Celsius (or 273 Kelvin for the physicists)
Actually physicists also take into account the PRESSURE as well as temperature, and given the current atmospheric pressure on Mars, water would vaporize at well below 273.15 K.;)
Ah, thanks. I can see that now. Without seing how the original arrays are initialized it's a little harder to see the particular usage. If I would have assumed the double buffer arrays were zeroed to start with...;)
BTW, I agree that documentation is very important at times, especially for high level design, although a very well written and object oriented program with well chosen class/method/field names can do an amazingly good job by itself. Most of my work now is Java based and the whole idea behind Javadoc is pretty slick and usefull, not to mention that IDEs like NetBeans do a great job of automating a lot of the busy work for you.
I looks fairly obvious that this is a simple blur algorithm with a static mask. Strange that the iteration limit and array sizes are hard coded though. Bad code... Bad bad code.;)
First of all, I wasn't the one talking about reflecting it back at the source. I was merely responding to a statement doubtful of microwave reflectors.
But, now that you mention it, large panels arranged as corner cube reflectors should be able to reflect an incoming microwave beam back toward the source rather nicely. No tracking system required.
It's my understanding that in the event of a total failure of a nuclear plant, the reactor will SCRAM automaticaly (control rods will fall and take the reactor sub-cruitical).
You know a material that makes a good mirror in the microwave range, please do tell.
Yes. How about a sheet of good conducting METAL. You know... like the kind they make microwave oven enclosures out of. You honestly didn't think the housing absorbed the microwave energy, did you?
... Why should [J.R.R. Tolkien's] work become public domain? What gives you the right to it?
What gives us the right? J.R.R. Tolkien gave us that right! He obtained a Copyright on the work which explicitly forces the work into the public domain after it expires. If he wasn't willing to let it pass into the public domain, he could have kept it to himself.
The microwave oven beam is directional only until it hits the "stirrer", a rotating paddle designed to spread the microwaves all over the interior of the oven
Just what kind of a microwave do you have? I've never seen ANY modern consumer microwave oven design with ANY type of mechanical 'stirring' device. Could you provide any sort of reference for your claim?:)
Most microwave ovens just let the microwaves bounce around the inside of the cavity and use a turntable to avoid the effects of EM nodes and anti-nodes causing hot/cold spots in the food.
...And, yes, I have disassembled a lot of consumer microwave ovens. The magnetrons are a great for building plasma generators.;)
You are right that this unit isn't the brightest, but this is an EXCELLENT projector for home theatre if you can get the room moderately dark.
The resolution of this thing will blow away anything currently available on the market (at least AFAIK, and I've done a LOT of searching.);) You just have to see a wall sized 1600x1200 or higher on this baby. These are multisync and will do a very respectable refresh rate, have excellend color, and can be driven via RGB, Component, S-Video and Composite. The resolutions you get by driving it with a computer via RGB will blow away any std. video (15kHz) DVD player around.
I makaged to pick one of these up at my local University Surplus Property Sale last summer for a whopping $15.;) They said it was broken, but it just had one of the main cards partially unplugged. WhoooHOoo!;)
Slashdot Mirror
Very well summarised. Thanks! ;)
Please don't take me wrong. I think we are in agreement, but I was merely drawing a distinction between the first definition and the fifth as illustrated below (courtesy Merrriam-Webster Online).
interference n.
2 : the mutual effect on meeting of two wave trains (as of light or sound) that constitutes alternating areas of increased and decreased amplitude (as light and dark lines or louder and softer sound)
5 a : confusion of a received radio signal due to the presence of noise (as atmospherics) or signals from two or more transmitters on a single frequency.
The point I was trying to make (and the point I think Reed was making) is that with the right type of receiver, you can recuce or eliminate such interference. Hence his statement that the interference is a limitation of the receiving device .
But Reed isn't using "interferrence" in this technical sense. He just means ...
Actually, I think Reed was using interference in exactly the sense that I'm talking about and, as you pointed out, ignores many of the real world implications of actually implementing the devices he's promoting.
In your crowded room analogy you can't hear what's being said because your ears hear in all directions (A limitation of the receiving equipment as Reed puts it). If your ears were directional like your eyes, you could eliminate virtually all the sound interference and could selectively listen to different people in the room (just as the people using sign language are able to because there eyes are direcional).
He's basically saying that using currenly common tv/radio antennas is like viewing the world with cataracts. (My analogy)
Nothing which Reed presents allows him to circumvent the Shannon limit ...
If you have an antenna that can selectively choose a source based on direction/polarization, then that source could use the full spectrum (ie. no fixed bandwidth) and the Shannon limit is irrelevant. ;)
These are dirrectional antennas that are able to do spatial seperation of signals electronically using signal processing (ie. without moving the antenna). They can also broadcast in any particular direction using the same phasing techniques.
They've already been around for quite a while (eg. NORAD) and with DSPs becoming so inexpensive a lot of work is being done on getting them into the private sector.
As I've said before, what some call 'radio interference', a physicist would call electromagnetic superposition. If there are ways to distinguish the signals via spatially or polarizationally sensitive antennas, then this so-called 'interference' can be eliminated.
What a communications engineer calls "radio interferance", a physicist would call electromagnetic superposition.
If you have an antenna that can't seperate out the superimposed signals, you get 'interferance'. While common radio and tv antenna's can't seperate these signals, other types of directional or polarization sensitive antennas can seperate out these signals so there is no interferance.
A lot of work has been and is currently being done on antennas where this can be all done electronically (ie. you don't have to reposition as you do with conventional directional antennas).
For more information, go do some reading on DSP controlled phased array antennas. ;)
Yes, but between any two different rational numbers there are infinitely MORE irrational numbers. ;)
His point was that our eyes DO seperate out spatially distinct signals. Common radio/TV antennas DON'T.
What people refer to as "radio interferance" is really just EM superposition and could be removed with an antenna that can sererate spatially distinct signals.
Now if you want to say that the wavelength of the most intensely radiated light is less than 700nm... ;)
Also, most people consider another defining characteristic of planets, which is ignored entirely by the above definition, to be that they're gravitationally bound to other objects.
Great! You've just classified virtually all minor stars in binary systems as planets! ;)
Personally I think we should keep the definition of planet as any non-stellar object orbiting a star. We should just add classes for features such as surface gravity, atmosphere orbital eccentricity, maybe even surface temperature.
An asteroid might be a class P planetoid. Jupiter might be class G3, or earth might be an M class planet. ;)
Then we'd be here arguing over just "How much atmosphere constitutes an atmosphere?", and to settle disputes, we'd need to use the Uniform Planetary-Class Dispute-Resolution Policy. ;)
Didn't anyone ever tell you that you're not supposed to place a period in the middle of a sentence? ;)
I was watching some 'scientists' dating a glacier flow on a PBS documentary. Since there was no organic matter, they took pieces of rock that had been torn off by the glacier and used radiometric dating on the rocks. They claimed that that was the age of the when the glacier had broken the rock away.
HELLO??? I know that there isn't a lot of cross over between geology and biology, but OUCH!!! Now if they had tried to guess the age of the fractured surface of the rock using some kind of oxidation rate or something, they might have been ballparkish. At the time, I just couldn't believe that any scientists could be that stupid. Of course now I know better. :)
You even have to be careful of experiments in quantum physics in refereed journals these days. Fields are highly specialized and sometimes explainations that would be obvious to some are overlooked by those writing the papers. You end up with all kinds of contradictions. Did you realize that treating the simultaneous collapse of a quantum wave function of entangled particles as a physical event is entirely inconsistent with the tenets of special relativity? Something's gotta give. ;)
No, We're FOR freedom... The freedom to NOT pay to propigate someone else's spam!!! Get a clue!
Actually, thanks to PBS, many non-Canadians WILL understand the humor. ;)
Actually physicists also take into account the PRESSURE as well as temperature, and given the current atmospheric pressure on Mars, water would vaporize at well below 273.15 K. ;)
The bar record for ROGER Grace shows the same e-mail address as listed on the previous E-Bay reports. This lookup can be found here.
BTW, I agree that documentation is very important at times, especially for high level design, although a very well written and object oriented program with well chosen class/method/field names can do an amazingly good job by itself. Most of my work now is Java based and the whole idea behind Javadoc is pretty slick and usefull, not to mention that IDEs like NetBeans do a great job of automating a lot of the busy work for you.
OK, I'm done rambling now. :)
I looks fairly obvious that this is a simple blur algorithm with a static mask. Strange that the iteration limit and array sizes are hard coded though. Bad code... Bad bad code. ;)
But, now that you mention it, large panels arranged as corner cube reflectors should be able to reflect an incoming microwave beam back toward the source rather nicely. No tracking system required.
It's my understanding that in the event of a total failure of a nuclear plant, the reactor will SCRAM automaticaly (control rods will fall and take the reactor sub-cruitical).
Yes. How about a sheet of good conducting METAL. You know... like the kind they make microwave oven enclosures out of. You honestly didn't think the housing absorbed the microwave energy, did you?
Ouch! They really should have chosen a different title for that page! There is virtually no information on that page at all.
Or is this all just a big joke?
What gives us the right? J.R.R. Tolkien gave us that right! He obtained a Copyright on the work which explicitly forces the work into the public domain after it expires. If he wasn't willing to let it pass into the public domain, he could have kept it to himself.
Just what kind of a microwave do you have? I've never seen ANY modern consumer microwave oven design with ANY type of mechanical 'stirring' device. Could you provide any sort of reference for your claim? :)
Most microwave ovens just let the microwaves bounce around the inside of the cavity and use a turntable to avoid the effects of EM nodes and anti-nodes causing hot/cold spots in the food.
The resolution of this thing will blow away anything currently available on the market (at least AFAIK, and I've done a LOT of searching.) ;) You just have to see a wall sized 1600x1200 or higher on this baby. These are multisync and will do a very respectable refresh rate, have excellend color, and can be driven via RGB, Component, S-Video and Composite. The resolutions you get by driving it with a computer via RGB will blow away any std. video (15kHz) DVD player around.
I makaged to pick one of these up at my local University Surplus Property Sale last summer for a whopping $15. ;) They said it was broken, but it just had one of the main cards partially unplugged. WhoooHOoo! ;)