but what I want to know, is why bother writing a detailed paper debunking something that is still experimental?
The guy who wrote the original paper is from Qualcomm- they have a strong interest in being at the forefront of technology. When a new technology like this comes up with such a great stated promise, if it has a remote possibility of being useful, it is in their best interest to investigate it. Otherwise, this situation will happen, which I have been on the receiving end of: Suit comes in for a project review and asks why we haven't been spending his limited money researching this latest and greatest technique he read about in a trade magazine. This causes a shake up all the way down to the people that actually do the work, we investigate, and find that our previous cursory investigation that showed that idea to be worthless was entirely accurate. Total time wasted- about a man month.
Mr. Karn was just doing his job for Qualcomm, and doing a service for the rest of us.
The Shannon-Hartley equation (usually referred to as Shannon's limit) is this:
capacity=bandwidth*log(base2)*(1+Signal/Noise)
The 33Kbit/second limit for a traditional analog/analog phone line comes from this- Signal/Noise is about 256:1 (8 bit sampling), 4KHz bandwidth-- capacity of a 4KHz phone line is about 32000 bits/second.
108MHz leading to 108MBit/sec would only be from simple on off keying- which makes no use of the signal/noise ratio. If you had about 48dB of S/N on 108MHz that leads to a capacity of 860 Mbit/second.
Neither MIPS or MHz is a truly accurate measure of the speed of a system, the problem is that no-one can agree on a standard. There are other much more mathematically rigorous measures, but which one will you choose? Are you going to measure integer, floating point, or vector processing? Bus speed? Cache hit rate? Unfortunately, the processing requirements for different applications vary as much as the applications themselves. Serving up web pages is a much different task than doing a 2-D FFT on a 16Kx16K floating point array. And processors and systems can be configured differently to do each efficiently.
Consistency is key- if website A compares processors with suite X of speed tests, you can only compare that test with other things done with suite X (and probably only with website A). MHz is a much easier and quicker way to compare. Just one number. Just not an accurate number.
Bluefin Robotics makes underwater autonomous robots. You may not like the pricing or availability, though. UT Applied Research Labs makes a version that lives on the surface of the ocean and listens for missle impacts in ICBM tests.
Just about any robot you want is out there if you look hard enough.
For their on-board LAN solutions on their servers, Dell uses Intel 10/100 (i82559). I believe that Dell uses 3Com for on board LAN on desktops, but I have no experience with them.
I have also heard stoies about what you can find in Japan- apparently the Japanese manufacturers use their home market as a testing ground for products before they export, down to little things like figuring out which button configuration is best on walkmans by trying out a bunch of otherwise identical models- but the big question is this- I've also heard that the Japanese companies charge much more for their products in their home market. Is this true?
Some chargers rely on the battery rise in temperature to determine when to shut off.
Very true- but the primary failure I've seen in battery packs (after the individual cells) is the temperature sensor (usu. on Ni-Cd packs). If the temp sensor goes bad, the charger never goes off, and you can destroy a good battery. Thankfully, good Li-ion battery chargers don't rely on temperature to determine charge.
Very true that heat is part of the charging process, excessive heat is the problem. Any more heat than is necessary is a bad thing.
The battery chargers for most devices today (cell phones, laptops, not the really cheap, bottom of the barrel stuff though) are pretty smart. The real charging circuitry is not in the battery or in the wall-wart- it is usually in the device itself. The wall wart is only a bulk power supply, to this end, let your device decide how to charge it. The thing to watch out for is excessive heat- which is what kills most batteries, especially ni-cads. Once the battery is charged, if the battery is still warm, it is being overcharged- time to disconnect it. Batteries don't like heat.
Lithium-ion batteries are pretty tough, but even with them, the less time spent on the charger the better- since chargers are inefficient, a significant amount of the power just goes to heating up the battery. If you don't really need to charge the battery, don't bother, the heat cycles (and excessive time spent hot) shorten the battery life.
When I post something, it pretty much becomes a matter of public record- it is out there, out of my control. The only proof of the date and time I posted it is as ephemeral as the text that I posted. And both can be easily changed by someone leaving no indication that the text has been changed.
Realistically, I don't think we should be held (legally) liable for those things that we post unless it has some sort of secure, verifable, signing mechanism- there is no way to tell who is really posting a message, or what has happened to it after it has left the author's system.
Delete = gone is nice- We have that option when it comes to shredders and incinerators for our paper correspondence, I think the concept has to be a bit more fleshed out to be truely applicable to the digital medium.
EMI? That's sort of unlikely for stuff running at low speeds and for circuits of that size. More likely it's a power supply problem.
Nope. The power supply was stiff and well filtered, and separate for both the motors and CPU. The motors were isolated from the CPU by relays (with the proper reverse EMF blocking diodes). Small DC brush motors put out a *lot* of noise, and apparently the ZX81 was pretty susceptible. The ZX81 put out a *lot* of noise itself, too, especially when I ran it without a case. but the EMI problems I had were there with or without the case.
I had a few and thought that they would make a pretty good controller board with the Z80 processor.
I did a project in high school (~1985) trying to use a ZX81 as a controller for a robot. It worked, kinda. Very susceptible to emi, especially the sort that small DC motors put off. It used technology that was "good" for the time, which translated to today's technology, means "slow and power hungry."
Other than the "vintage-cool" factor, as a controller, you can do a whole lot more with a modern microcontroller. More I/O, similar amount of memory, much more in terms of MIPS/W. You do lose the video display and the ability to program it in BASIC.
The ZX81 was a great hack. The ability to implement a GUI (it did output to a TV) and an interpreter with that little amount of processing horsepower, RAM and ROM is a pretty impressive feat, especially keeping it relatively cheap.
I think that we could all learn something from the ZX81- it is amazing how far you can stretch your resources when you don't have many. The real power of such knowledge is knowing when it is appropriate to use it.
I don't think DES will be phased out anytime soon, especially in the military. They may be fewer new implementations of it though. DES is built into many systems that are extremely hard and/or expensive to replace, such as the encrypted precise GPS code P(Y). I don't believe that it would be possible to upgrade the satellites remotely, and there is already a huge installed base of users that rely on the technology.
I think it boils down to this- you have to find out about your customers migration plan first. DES will be around for a while longer, yet.
I've had DSL through Southwestern Bell and jump.net since January of this year, and it has been pretty painless. There are loads of different providers in the area (Austin, TX, USA), but jump.net was the only one to offer a static IP and no restrictions on servers. I do pay a bit of a premium, and my service is not as fast (384K down / 128K up) as other ISPs seem to provide in my area.
Installation was done by southwestern bell, and was in place 3 or 4 weeks after I ordered it, and it was operational on the day of installation. I have had only a few problems (once their DNS went down, when I called they told me they were rebooting it and to try again in a few minutes, and it worked shortly thereafter, and I lost connectivity another time for a few hours). Jump.net appears to be a comfortable size that they can personally and rapidly fix the problems that come up. They have techs who actually answer the phone- when I have had to call, I did not get stuck in voice mail hell. The huge providers may be able to undercut the others on price, but they are going to have a harder time beating them on service.
Since I had DSL installed early, I've avoided many of the painful waits that people are experiencing around here.
The general rule of thumb for accuracy is that your lat/long will be about twice as accurate as your altitude. GPS receivers compute a figure of merit as to the expected accuracy of the solution- It is the residual of an over-determined set of linear equations. In general, the better the geometry of the SV (GPS satellite) constellation, the smaller your residual will be. The calculation of the altitude sucks because of the poor geometry of the calculation- you're trying to triangulate to a bunch of things essentially in the same plane, high above you (all in the +Z direction). You want to get some SVs in your calculation that are near the horizon, but the accuracy there will be off due to ionospheric differences, which is why the GPS system is a dual frequency system, the two frequencies give you ionospheric corrections. Unfortunately, no (commercial) handheld and only a few surverying receivers are dual frequency because only the Y code (encrypted P, or precise code) is on the second GPS frequency, and only the military has access to the crypto-keys for GPS. Some surveying receivers correlate between the two frequencies to determine the ionospheric correction factor, but this is not a trivial task: real time correlation between two 10 Mbit data streams.
But what I was trying to lead to- differential or or not, you're still working with the same basic constellation (no subterranean SVs yet), and your altitude will always be half as accurate as your lat/long.
What I'm unsure about is how much differential GPS helps out CA code receivers now that SA is turned off. With SA on, the effect was dramatic. For real precision, I don't know of any receivers that work well on a moving platform, since a large part of precision with a high quality CA code receiver is essentially just averaging. You have an inherent limit with a CA receiver since the raw code is a 1Mbit code.
Most of this is recollection from a seminar I took from Navetech about 3 years ago.
DGPS is unnecessary especially in flight- It will get you to sub meter level accuracy, and that is far more accurate than I hope air traffic control will ever need. Airplanes (esp. the big ones) already have very good radar based altimiters/ground speed indicators that will get them better altitude and speed than GPS really has a hope for. There may be some use for DGPS for control on the taxiways, but realistically, they should be keeping much further apart than 10M, so it wouldn't make a significant difference.
These planes still have pilots, and they still and should have the final say over these technologies, especially when lives are at stake.
The article this refers to mentions nothing I can find about DGPS. DGPS would just make it more complex and vulernable to failure, both incidental and intentional.
There are spares already up there, ready to be moved into the proper orbit when needed. GPS is a vital technology for the US military- they have lives depending on it already. What bothers me is the dependence on just one technology. Yeah use GPS, but have a backup (VFR?) ready for when something gets screwed up.
The whole uproar is a bit of a payback for DC sending out Cease and Desist letters to curtail hacking the device they sent out (unsolicited). They have attempted to sneak in a license that many believe is unfair.
If no one fights it, this sort of action will become the rule. They have lawers and some laws on their side, but there are other laws that apply, and for this fight to become legitimate in the eyes of the public at large, the battle has to be taken up with established means, in this case, the law as it concerns the US Postal Service.
Ok, lets say I opt-out. DC also has this clause on their website (from this page):
Information may be changed or updated without notice. Digital:Convergence may also make improvements and/or changes in the products and/or described in this information at any time without notice.
Which leads me to believe that they can, like Amazon, change the terms at a whim to something more beneficial to them.
If you trust them to have your best interests in mind, go ahead. They are a company. Their responsibility is to their investors, which generally is to maximize their investment. Preserving your rights is not necessarily part of their buisness plan, and if it is included in there, it can just as easily be removed.
I received a CueCat in the mail. I have accepted no license, and I don't plan to. I'm not going to install their software by any means. They have given me no ability to refuse the terms of their license. It was sent to me without any action on my part, other than being a subscriber to a magazine- that sounds like a gift to me.
They have the broad statement of (2) using the:CueCat reader leading to my acceptance of the license. But what do they mean by using it? Using it as a doorstop? Paperweight?
I really hope this issue comes around and hurts them in the end. They must have spent a *huge* amount of money to get this out. They probably have 100's of thousands sitting in a warehouse somewhere, ready to be shipped. I hope they never get to ship them.
Hmm... a thought. Can I refuse their terms with an email that states that if their email server accepts the message, they accept my terms? That sounds a lot like the arbitrary acceptance conditions that they put forth.
Electromagnetic radiation (EMR) is a magnetic field moving at right-angles to an electrical field. (Hence the inclusion of BOTH terms.)
Actually, no, the electric field is at right angles to the magnetic field- as given by one of Maxwell's laws: (del) x E = -(the partial derivative of B with respect to t) Where E is the vector electric field and B is the magnetic flux density.
Magnetic fields NOT induced by the movement of an electrical field include virtually all non-ferrous magnetic material, such as magnetostars, superconductors (where electrical fields have no meaning, in a classical sense), and all EMR of greater frequency than about mid X-Ray, which is all generated within the nucleus, and not through the collapse of electrons from one orbital to anothe
Please read my post more carefully, I did not say that magnetic fields were induced by the movement of an electrical field- all magnetic fields are induced by the movement of electric(ally charged) particles. Until you find a magnetic monopole, that will be the case. (as given by another of Maxwell's laws: (del)(dot)B=0. In your example, the electrons are moving as the atom changes state.
Look at Ampere's circuital law: (line integral)H(dot)dl=I : a line integral of static magnetic field taken about any given closed path must equal the (electrical) current enclosed by that path.
A superconductor has no magnetic field *inside* it, but there is plenty of magnetic field around it, caused by (any only by) movement of electrons in the superconductor. Actually there is no *electric* field inside a perfect conductor, either.
First, microwaves (and indeed any EMR) affects ONLY those molecules that correspond to that wavelength.
Like water. Cellular phones (esp. PCS, around 1.9 GHz) are pretty close to the frequency that is proven effective for heating things- like microwave ovens (~2.4 GHz).
Secondly, the chances are that it's not an EMR effect at all. The magnetic fields of cell phones are probably much more important than microwave emissions.
Think about the acronyms you use before you use them- EMR - electro MAGNETIC radiation. They go together. Yes, different things affect the electical and magnetic fields differently, but magnetic fields are always generated by the motion of electric particles (since no one has found any magnetic monopoles yet, or evidence of them).
Actually, it works both ways. Many infra-red LEDs (particularly the very bright ones) have some visible light output. I have a VCR remote control that I can see the output from in a darkened room, if I look directly at the die. I've been able to see light from many clear packaged IR LEDs (without a filter window in front of it). The vast majority of the energy is still going to the IR component of the light, as demonstrated by an IR flourescent detector, in my case.
LEDs are not spectrally pure, they put out light over a range of wavelengths. The wavelength given for a particular LED is just the center of the band. Just as visible LEDs have output in the IR region, the IRLEDs have output in the visible region. The dark window/encapsulant of the IR LEDs block the majority of the visible light.
But since I don't have a cuecat- I have no idea which applies in this case. If the light output of the cuecat is dim, I'd guess that it is actually IR, since they want to get as much power output as possible, to get the best signal/noise ratio at their detector. IR LEDs are usually a better choice because they are much more efficient than visible LEDs in terms of candelas/milli-amp.
You don't need college to do a lot of things. But what it can help with is your ability to change the focus and direction of your career. In college you can learn a variety of things. Usually, you don't know what is going to be beneficial tomorrow, next year, or 20 years from now. It also helps you with the discipline to learn the really hard stuff. Often, you will be able to make connections between the skills and knowledge you have-- which leads to innovation.
It is kinda like the difference between a "professional" and a skilled tradesman. Usually the professional has a broader knowledge base and the ability to combine skills from a diverse background to solve the problem. The tradesman knows a few skills of the trade *really well* It is usually harder for the skilled tradesman to adapt to new situations.
I work as an electrical engineer. I can do a lot of things, code, design circuits, layout printed circuit boards, and so on. What usually makes engineers (usually, but not always, college educated) different from technicians (usually, but not always, non-college educated) is the ability to use all of these skills at the same time. I have worked with technicians that are much better at one or two of those individual pieces (layout, design, coding), but lack the skills and background to tie them all together. An engineering education, in particular, gave me skills to evaluate alternative solutions to the problems that come up: Should I try an analog solution? A discrete digital solution? A microcontroller? A DSP? I have enough background so that I can figure out which one may work the best.
Anyone who thinks that they are going to be doing the same thing for the rest of their career is taking an awfully narrow view of the future. There is no certainty that any career will last forever, despite what the Unions try. Someday, it may just be easier and cheaper to send all those Java programming jobs overseas. By that time, we may have Programmers Unions lobbying to keep the current languages, though they may be obsolete, their rank-and-file know them really well, and don't have the urge to learn something else.
Take a lesson from the professional athletes: You may be the best and fastest right now. You can command huge a huge salary right now. But the skills that brought you that salary could fade, or be eclipsed by some other bright young chap that has newer, better skills. You may not be on the top of the heap forever, so plan ahead.
Did you have a look at the actual article? There is a nice diagram... More details in the article.
Looked at it, but I had to change the settings on my display to see the numbers on the left side of the graph, so I missed that graph on my first reading. It just starts at 10^10 Watts. That's 10 billion watts, effective radiated power. I can't see that any civilization short of the level of building Dyson Spheres would have that much energy to just throw around.
I disagree with the implication that a higher level civilization would be transmitting that much power. We've gotten much more efficient with our bandwidth and power utilization, I have no doubt that a more advanced civilization would too. They probably have to deal with finite resources, just as we do.
But I think that this establishes that whoever is out there, they have to be trying to talk to us. We won't hear their analogue to TV or radio.
Something I've never seen is any information about how powerful the extraterrestrial signals have to be for us to hear them- to do that, we need to know how much gain the receiving antenna has, what the sensitivity of the receiver is, and the intensity of the background noise. From that information we can get an idea of what sort of transmitters (at what distance) we're looking for. For example, a big radio station in the US is about 100KW, with antennas that point the signal more or less to the horizon. We make it a point not to send too much energy up- the intensity pointing straight up at the sky is many dB down from the main lobe. Just how far away could the Aricibo antenna hear a station that had an effective 1KW (isotropic) pointed in their direction?
Of course the Aricibo antenna doesn't listen at the frequencies of FM radio, it listens to signals in the microwave region (for SETI work, from what I understand). At these frequencies, it is even easier to point the signal from an antenna. Unless someone is broadcasting to us intentionally, I have a feeling we're never going to hear them.
There has been much talk about how we've been broadcasting to the universe- but at stellar distances, all those signals are going to look like they're coming from the same point, albeit diverse in frequency. But everything at the same frequency gets added together- and if you add enough non-correlated signals together- guess what: it looks like noise! Can our signals compete with the EM noise put out by the Sun?
Another thing: as our technology improves, our signals look more and more like noise, and we use less effective power- consider any sort of spread spectrum- the energy has been spread out over a wide area to combat interference, lowering the peak power at any one frequency. At the same time we're making improvements with our receivers so that we don't need to transmit as much power. It all ends up as more efficient use of what we have (more bandwidth for the same power) I can't think of any expanding intelligence that couldn't see the utility of that- so as an intelligent race expands, the overall amount of unintended radiation may not go up proportinately.
On the other hand, I support SETI- I've got it running on 4 machines, and I've completed over 350 SETI@Home work units. If we don't look, we won't find anything until they land on the White House lawn. These are just some things I've been thinking about.
Slashdot Mirror
but what I want to know, is why bother writing a detailed paper debunking something that is still experimental?
The guy who wrote the original paper is from Qualcomm- they have a strong interest in being at the forefront of technology. When a new technology like this comes up with such a great stated promise, if it has a remote possibility of being useful, it is in their best interest to investigate it. Otherwise, this situation will happen, which I have been on the receiving end of: Suit comes in for a project review and asks why we haven't been spending his limited money researching this latest and greatest technique he read about in a trade magazine. This causes a shake up all the way down to the people that actually do the work, we investigate, and find that our previous cursory investigation that showed that idea to be worthless was entirely accurate. Total time wasted- about a man month.
Mr. Karn was just doing his job for Qualcomm, and doing a service for the rest of us.
The Shannon-Hartley equation (usually referred to as Shannon's limit) is this:
capacity=bandwidth*log(base2)*(1+Signal/Noise)
The 33Kbit/second limit for a traditional analog/analog phone line comes from this- Signal/Noise is about 256:1 (8 bit sampling), 4KHz bandwidth-- capacity of a 4KHz phone line is about 32000 bits/second.
108MHz leading to 108MBit/sec would only be from simple on off keying- which makes no use of the signal/noise ratio. If you had about 48dB of S/N on 108MHz that leads to a capacity of 860 Mbit/second.
Neither MIPS or MHz is a truly accurate measure of the speed of a system, the problem is that no-one can agree on a standard. There are other much more mathematically rigorous measures, but which one will you choose? Are you going to measure integer, floating point, or vector processing? Bus speed? Cache hit rate? Unfortunately, the processing requirements for different applications vary as much as the applications themselves. Serving up web pages is a much different task than doing a 2-D FFT on a 16Kx16K floating point array. And processors and systems can be configured differently to do each efficiently.
Consistency is key- if website A compares processors with suite X of speed tests, you can only compare that test with other things done with suite X (and probably only with website A). MHz is a much easier and quicker way to compare. Just one number. Just not an accurate number.
Bluefin Robotics makes underwater autonomous robots. You may not like the pricing or availability, though. UT Applied Research Labs makes a version that lives on the surface of the ocean and listens for missle impacts in ICBM tests.
Just about any robot you want is out there if you look hard enough.
For their on-board LAN solutions on their servers, Dell uses Intel 10/100 (i82559). I believe that Dell uses 3Com for on board LAN on desktops, but I have no experience with them.
I have also heard stoies about what you can find in Japan- apparently the Japanese manufacturers use their home market as a testing ground for products before they export, down to little things like figuring out which button configuration is best on walkmans by trying out a bunch of otherwise identical models- but the big question is this- I've also heard that the Japanese companies charge much more for their products in their home market. Is this true?
Some chargers rely on the battery rise in temperature to determine when to shut off.
Very true- but the primary failure I've seen in battery packs (after the individual cells) is the temperature sensor (usu. on Ni-Cd packs). If the temp sensor goes bad, the charger never goes off, and you can destroy a good battery. Thankfully, good Li-ion battery chargers don't rely on temperature to determine charge.
Very true that heat is part of the charging process, excessive heat is the problem. Any more heat than is necessary is a bad thing.
The battery chargers for most devices today (cell phones, laptops, not the really cheap, bottom of the barrel stuff though) are pretty smart. The real charging circuitry is not in the battery or in the wall-wart- it is usually in the device itself. The wall wart is only a bulk power supply, to this end, let your device decide how to charge it. The thing to watch out for is excessive heat- which is what kills most batteries, especially ni-cads. Once the battery is charged, if the battery is still warm, it is being overcharged- time to disconnect it. Batteries don't like heat.
Lithium-ion batteries are pretty tough, but even with them, the less time spent on the charger the better- since chargers are inefficient, a significant amount of the power just goes to heating up the battery. If you don't really need to charge the battery, don't bother, the heat cycles (and excessive time spent hot) shorten the battery life.
When I post something, it pretty much becomes a matter of public record- it is out there, out of my control. The only proof of the date and time I posted it is as ephemeral as the text that I posted. And both can be easily changed by someone leaving no indication that the text has been changed.
Realistically, I don't think we should be held (legally) liable for those things that we post unless it has some sort of secure, verifable, signing mechanism- there is no way to tell who is really posting a message, or what has happened to it after it has left the author's system.
Delete = gone is nice- We have that option when it comes to shredders and incinerators for our paper correspondence, I think the concept has to be a bit more fleshed out to be truely applicable to the digital medium.
EMI? That's sort of unlikely for stuff running at low speeds and for circuits of that size. More likely it's a power supply problem.
Nope. The power supply was stiff and well filtered, and separate for both the motors and CPU. The motors were isolated from the CPU by relays (with the proper reverse EMF blocking diodes). Small DC brush motors put out a *lot* of noise, and apparently the ZX81 was pretty susceptible. The ZX81 put out a *lot* of noise itself, too, especially when I ran it without a case. but the EMI problems I had were there with or without the case.
I had a few and thought that they would make a pretty good controller board with the Z80 processor.
I did a project in high school (~1985) trying to use a ZX81 as a controller for a robot. It worked, kinda. Very susceptible to emi, especially the sort that small DC motors put off. It used technology that was "good" for the time, which translated to today's technology, means "slow and power hungry."
Other than the "vintage-cool" factor, as a controller, you can do a whole lot more with a modern microcontroller. More I/O, similar amount of memory, much more in terms of MIPS/W. You do lose the video display and the ability to program it in BASIC.
The ZX81 was a great hack. The ability to implement a GUI (it did output to a TV) and an interpreter with that little amount of processing horsepower, RAM and ROM is a pretty impressive feat, especially keeping it relatively cheap.
I think that we could all learn something from the ZX81- it is amazing how far you can stretch your resources when you don't have many. The real power of such knowledge is knowing when it is appropriate to use it.
I don't think DES will be phased out anytime soon, especially in the military. They may be fewer new implementations of it though. DES is built into many systems that are extremely hard and/or expensive to replace, such as the encrypted precise GPS code P(Y). I don't believe that it would be possible to upgrade the satellites remotely, and there is already a huge installed base of users that rely on the technology.
I think it boils down to this- you have to find out about your customers migration plan first. DES will be around for a while longer, yet.
I've had DSL through Southwestern Bell and jump.net since January of this year, and it has been pretty painless. There are loads of different providers in the area (Austin, TX, USA), but jump.net was the only one to offer a static IP and no restrictions on servers. I do pay a bit of a premium, and my service is not as fast (384K down / 128K up) as other ISPs seem to provide in my area.
Installation was done by southwestern bell, and was in place 3 or 4 weeks after I ordered it, and it was operational on the day of installation. I have had only a few problems (once their DNS went down, when I called they told me they were rebooting it and to try again in a few minutes, and it worked shortly thereafter, and I lost connectivity another time for a few hours). Jump.net appears to be a comfortable size that they can personally and rapidly fix the problems that come up. They have techs who actually answer the phone- when I have had to call, I did not get stuck in voice mail hell. The huge providers may be able to undercut the others on price, but they are going to have a harder time beating them on service.
Since I had DSL installed early, I've avoided many of the painful waits that people are experiencing around here.
The general rule of thumb for accuracy is that your lat/long will be about twice as accurate as your altitude. GPS receivers compute a figure of merit as to the expected accuracy of the solution- It is the residual of an over-determined set of linear equations. In general, the better the geometry of the SV (GPS satellite) constellation, the smaller your residual will be. The calculation of the altitude sucks because of the poor geometry of the calculation- you're trying to triangulate to a bunch of things essentially in the same plane, high above you (all in the +Z direction). You want to get some SVs in your calculation that are near the horizon, but the accuracy there will be off due to ionospheric differences, which is why the GPS system is a dual frequency system, the two frequencies give you ionospheric corrections. Unfortunately, no (commercial) handheld and only a few surverying receivers are dual frequency because only the Y code (encrypted P, or precise code) is on the second GPS frequency, and only the military has access to the crypto-keys for GPS. Some surveying receivers correlate between the two frequencies to determine the ionospheric correction factor, but this is not a trivial task: real time correlation between two 10 Mbit data streams.
But what I was trying to lead to- differential or or not, you're still working with the same basic constellation (no subterranean SVs yet), and your altitude will always be half as accurate as your lat/long.
What I'm unsure about is how much differential GPS helps out CA code receivers now that SA is turned off. With SA on, the effect was dramatic. For real precision, I don't know of any receivers that work well on a moving platform, since a large part of precision with a high quality CA code receiver is essentially just averaging. You have an inherent limit with a CA receiver since the raw code is a 1Mbit code.
Most of this is recollection from a seminar I took from Navetech about 3 years ago.
DGPS is unnecessary especially in flight- It will get you to sub meter level accuracy, and that is far more accurate than I hope air traffic control will ever need. Airplanes (esp. the big ones) already have very good radar based altimiters/ground speed indicators that will get them better altitude and speed than GPS really has a hope for. There may be some use for DGPS for control on the taxiways, but realistically, they should be keeping much further apart than 10M, so it wouldn't make a significant difference.
These planes still have pilots, and they still and should have the final say over these technologies, especially when lives are at stake.
The article this refers to mentions nothing I can find about DGPS. DGPS would just make it more complex and vulernable to failure, both incidental and intentional.
Hot spare's in the sky and on the ground maybe?
There are spares already up there, ready to be moved into the proper orbit when needed. GPS is a vital technology for the US military- they have lives depending on it already. What bothers me is the dependence on just one technology. Yeah use GPS, but have a backup (VFR?) ready for when something gets screwed up.
The whole uproar is a bit of a payback for DC sending out Cease and Desist letters to curtail hacking the device they sent out (unsolicited). They have attempted to sneak in a license that many believe is unfair.
If no one fights it, this sort of action will become the rule. They have lawers and some laws on their side, but there are other laws that apply, and for this fight to become legitimate in the eyes of the public at large, the battle has to be taken up with established means, in this case, the law as it concerns the US Postal Service.
Which leads me to believe that they can, like Amazon, change the terms at a whim to something more beneficial to them.
If you trust them to have your best interests in mind, go ahead. They are a company. Their responsibility is to their investors, which generally is to maximize their investment. Preserving your rights is not necessarily part of their buisness plan, and if it is included in there, it can just as easily be removed.
I received a CueCat in the mail. I have accepted no license, and I don't plan to. I'm not going to install their software by any means. They have given me no ability to refuse the terms of their license. It was sent to me without any action on my part, other than being a subscriber to a magazine- that sounds like a gift to me.
:CueCat reader leading to my acceptance of the license. But what do they mean by using it? Using it as a doorstop? Paperweight?
They have the broad statement of (2) using the
I really hope this issue comes around and hurts them in the end. They must have spent a *huge* amount of money to get this out. They probably have 100's of thousands sitting in a warehouse somewhere, ready to be shipped. I hope they never get to ship them.
Hmm... a thought. Can I refuse their terms with an email that states that if their email server accepts the message, they accept my terms? That sounds a lot like the arbitrary acceptance conditions that they put forth.
Electromagnetic radiation (EMR) is a magnetic field moving at right-angles to an electrical field. (Hence the inclusion of BOTH terms.)
Actually, no, the electric field is at right angles to the magnetic field- as given by one of Maxwell's laws: (del) x E = -(the partial derivative of B with respect to t) Where E is the vector electric field and B is the magnetic flux density.
Magnetic fields NOT induced by the movement of an electrical field include virtually all non-ferrous magnetic material, such as magnetostars, superconductors (where electrical fields have no meaning, in a classical sense), and all EMR of greater frequency than about mid X-Ray, which is all generated within the nucleus, and not through the collapse of electrons from one orbital to anothe
Please read my post more carefully, I did not say that magnetic fields were induced by the movement of an electrical field- all magnetic fields are induced by the movement of electric(ally charged) particles. Until you find a magnetic monopole, that will be the case. (as given by another of Maxwell's laws: (del)(dot)B=0. In your example, the electrons are moving as the atom changes state.
Look at Ampere's circuital law: (line integral)H(dot)dl=I : a line integral of static magnetic field taken about any given closed path must equal the (electrical) current enclosed by that path.
A superconductor has no magnetic field *inside* it, but there is plenty of magnetic field around it, caused by (any only by) movement of electrons in the superconductor. Actually there is no *electric* field inside a perfect conductor, either.
First, microwaves (and indeed any EMR) affects ONLY those molecules that correspond to that wavelength.
Like water. Cellular phones (esp. PCS, around 1.9 GHz) are pretty close to the frequency that is proven effective for heating things- like microwave ovens (~2.4 GHz).
Secondly, the chances are that it's not an EMR effect at all. The magnetic fields of cell phones are probably much more important than microwave emissions.
Think about the acronyms you use before you use them- EMR - electro MAGNETIC radiation. They go together. Yes, different things affect the electical and magnetic fields differently, but magnetic fields are always generated by the motion of electric particles (since no one has found any magnetic monopoles yet, or evidence of them).
Actually, it works both ways. Many infra-red LEDs (particularly the very bright ones) have some visible light output. I have a VCR remote control that I can see the output from in a darkened room, if I look directly at the die. I've been able to see light from many clear packaged IR LEDs (without a filter window in front of it). The vast majority of the energy is still going to the IR component of the light, as demonstrated by an IR flourescent detector, in my case.
LEDs are not spectrally pure, they put out light over a range of wavelengths. The wavelength given for a particular LED is just the center of the band. Just as visible LEDs have output in the IR region, the IRLEDs have output in the visible region. The dark window/encapsulant of the IR LEDs block the majority of the visible light.
But since I don't have a cuecat- I have no idea which applies in this case. If the light output of the cuecat is dim, I'd guess that it is actually IR, since they want to get as much power output as possible, to get the best signal/noise ratio at their detector. IR LEDs are usually a better choice because they are much more efficient than visible LEDs in terms of candelas/milli-amp.
You don't need college to do a lot of things. But what it can help with is your ability to change the focus and direction of your career. In college you can learn a variety of things. Usually, you don't know what is going to be beneficial tomorrow, next year, or 20 years from now. It also helps you with the discipline to learn the really hard stuff. Often, you will be able to make connections between the skills and knowledge you have-- which leads to innovation.
It is kinda like the difference between a "professional" and a skilled tradesman. Usually the professional has a broader knowledge base and the ability to combine skills from a diverse background to solve the problem. The tradesman knows a few skills of the trade *really well* It is usually harder for the skilled tradesman to adapt to new situations.
I work as an electrical engineer. I can do a lot of things, code, design circuits, layout printed circuit boards, and so on. What usually makes engineers (usually, but not always, college educated) different from technicians (usually, but not always, non-college educated) is the ability to use all of these skills at the same time. I have worked with technicians that are much better at one or two of those individual pieces (layout, design, coding), but lack the skills and background to tie them all together. An engineering education, in particular, gave me skills to evaluate alternative solutions to the problems that come up: Should I try an analog solution? A discrete digital solution? A microcontroller? A DSP? I have enough background so that I can figure out which one may work the best.
Anyone who thinks that they are going to be doing the same thing for the rest of their career is taking an awfully narrow view of the future. There is no certainty that any career will last forever, despite what the Unions try. Someday, it may just be easier and cheaper to send all those Java programming jobs overseas. By that time, we may have Programmers Unions lobbying to keep the current languages, though they may be obsolete, their rank-and-file know them really well, and don't have the urge to learn something else.
Take a lesson from the professional athletes: You may be the best and fastest right now. You can command huge a huge salary right now. But the skills that brought you that salary could fade, or be eclipsed by some other bright young chap that has newer, better skills. You may not be on the top of the heap forever, so plan ahead.
Did you have a look at the actual article? There is a nice diagram... More details in the article.
Looked at it, but I had to change the settings on my display to see the numbers on the left side of the graph, so I missed that graph on my first reading. It just starts at 10^10 Watts. That's 10 billion watts, effective radiated power. I can't see that any civilization short of the level of building Dyson Spheres would have that much energy to just throw around.
I disagree with the implication that a higher level civilization would be transmitting that much power. We've gotten much more efficient with our bandwidth and power utilization, I have no doubt that a more advanced civilization would too. They probably have to deal with finite resources, just as we do.
But I think that this establishes that whoever is out there, they have to be trying to talk to us. We won't hear their analogue to TV or radio.
Here's some thoughts I've had about SETI:
Something I've never seen is any information about how powerful the extraterrestrial signals have to be for us to hear them- to do that, we need to know how much gain the receiving antenna has, what the sensitivity of the receiver is, and the intensity of the background noise. From that information we can get an idea of what sort of transmitters (at what distance) we're looking for. For example, a big radio station in the US is about 100KW, with antennas that point the signal more or less to the horizon. We make it a point not to send too much energy up- the intensity pointing straight up at the sky is many dB down from the main lobe. Just how far away could the Aricibo antenna hear a station that had an effective 1KW (isotropic) pointed in their direction?
Of course the Aricibo antenna doesn't listen at the frequencies of FM radio, it listens to signals in the microwave region (for SETI work, from what I understand). At these frequencies, it is even easier to point the signal from an antenna. Unless someone is broadcasting to us intentionally, I have a feeling we're never going to hear them.
There has been much talk about how we've been broadcasting to the universe- but at stellar distances, all those signals are going to look like they're coming from the same point, albeit diverse in frequency. But everything at the same frequency gets added together- and if you add enough non-correlated signals together- guess what: it looks like noise! Can our signals compete with the EM noise put out by the Sun?
Another thing: as our technology improves, our signals look more and more like noise, and we use less effective power- consider any sort of spread spectrum- the energy has been spread out over a wide area to combat interference, lowering the peak power at any one frequency. At the same time we're making improvements with our receivers so that we don't need to transmit as much power. It all ends up as more efficient use of what we have (more bandwidth for the same power) I can't think of any expanding intelligence that couldn't see the utility of that- so as an intelligent race expands, the overall amount of unintended radiation may not go up proportinately.
On the other hand, I support SETI- I've got it running on 4 machines, and I've completed over 350 SETI@Home work units. If we don't look, we won't find anything until they land on the White House lawn. These are just some things I've been thinking about.