The reason that bit bit depth is proportional to dynamic range would require understanding about how A/D's work. If you have only 8 bits that runs at a supply voltage of 1 volt, then the smallest voltage change able to detected at the one bit level would be only 1/256 = 3.922 mV (or converting to dB -48.13 dB). Compare that to a 16 bits and you get a resolution of 1/16^2 = 15.26 uV or -96.33 dB. When the music get quite enough, say the change is at 2 mV from one point in time to another. The 8 bit A/D will not be able to perceive the change, but the second A/D will be able. To say that an 8 bit A/D can give you 140 dB of dynamic range is just wrong. Even a 16 bit A/D cannot give you 140 dB of dynamic range.
All of this is discounting the effects of noise which will reduce the effective dynamic range also of the A/D. The term here to look for is called ENOB (or effective number of bits).
I think what you are trying to explain is that given the 8 bit A/D, you have to choose where you want your "sweet spot" to be, because in reality you will be capturing something which has a larger dynamic range than what you can capture. Since you only ~48 dB of dynamic range, If you choose an extreme such that the loudest level you can hear can be recorded without saturating your receiver which leads to distortion, then you will not be able to hear the quiet sounds. Conversely, if you decide you want to hear the quietest sounds, then you will saturate your receiver and the sound will be distorted.
You say to provide a source, but this just fundamental receiver design principles, and by receiver I mean RF, Audio, and Video. You can probably find the most on this topic from an RF perspective.
It's funny you mention the "Everyday Math". I live in the Chicago suburbs, so it seems every person I know that has a kid in grade school in the area is using this series of books for math. I have gone over my sisters house and there have been times where I have been asked to help my niece with her homework because my sister didn't know how to solve the problem since it is so different than how we were taught. Since I have a MSEE and have taken just a few math classes, and even I have to think about how to explain it to here without going over her head. So my first response is to ask where is the text book. I figure this is a good start to see what has been covered so far. She is unable to provide one, because it seems that everything is a worksheet.
I still remember the problem. It goes something like this: "People are on the phone in the US for a total of 123 billion minutes each day. If there are 200 million people with phones, what is the average amount of time each person is on the phone". I am sure for you and I this is a trivial problem, but here is what I have issue with it. First, I asked my niece if she knew what an average was. She said no. Ok, not a big deal so I tried to explain to her what an average was. My second issue with the problem was found out from trying to help her again. I asked her if she knew what factoring was. A blank stare is all I received for that. I didn't even bother asking about scientific notation*. So that leaves the only practical way to solve this is with long division, which I don't necessarily think that is wrong but to me detracts from what they might actually be trying to teach.
So that leads me to my issue with this problem and with "Everyday Math" in general. What is that they are trying to teach in this problem? Is it to explain the concept of an average? Is it how to do tedious long division? I can understand wanting to cross apply different math techniques to solving problems, but if neither concept has been taught then is either concept really being taught by the cross application? If anything, my impression from Everyday Math based on what I have seen is a removal of formalism to math. I know, how boring is it to talk about the associative property or commutative property, but if you have those tools under your belt then everyone is speaking the same language when it comes to math. And given that, then I think I could have helped her to solve this problem in a more algorithmic way. The idea of an average on the other hand needs to be taught in a different way than in just a word problem for kids her age (btw, she is now is 6th grade). Something as easy as rolling a die 10 times and summing the value and dividing by the total number of rolls. Or measuring the height of all the kids in class to find the average, and so on.
Now back to other issue of bad teachers. I would love to be a teacher of either math or physics, but guess what? They won't pay me as well to be a teacher as I can make being an engineer. Not that it is all about the money, but it certainly is an important factor especially when I can pull in twice what an average teacher makes. Since schools are so heavily unionized (at in Chicagoland) there is no way the union would allow disparate rate for math or physics teachers than the others. I think if you fix this problem, then I think there will be better recruiting of good teachers.
*Now I know this is slashdot, so I expect some snarky comments about her maybe not being that good in math. That's fair, but I know that on her report card she had a B+ in math recently, so that would put her at above average in the class. Then again, this could be a whole other discussion on grade inflation in the US.
Mod this up. I was in the Navy for 6 years. I also took advantage of the GI bill and went to a large state university when I left the military. Talk about some of the best times ever. in addition to being able to appreciated the education that you are being given (paying for it yourself also is a good motivator for that), I found it very relaxing compared to the military and a good transition back to civilian life.
One big reason that AC is used by power companies is the ease of transport. In electrical systems, power is lost in the form of R*I*I. Since the copper will always have some trace amounts of resistance, the power loss will go up with current squared. The main advantage that AC has over DC is the ease of which you can switch from one voltage to another. In theory, higher voltages will allow for less current for the same amount of power delivered. For AC, it is just a matter of using a transformer, which is completely passive and can handle large amounts of power. If you were to transmit DC, you would need something a lot more complex to get the voltage to a suitable level. One method would be a DC-DC or DC-AC motor. Another means would be a static inverter to go to AC or use a switch mode power supply to get to DC. However, this doesn't avoid the fact that they are more expensive when compared to a transformer.
Additionally, consumer electronics all have varying voltage requirements internal to their systems. A transformer scales well in size, so to then get to DC, transform the voltage to slightly higher from where you want the DC, use 4 (or 2) diodes for rectification, possibly a zener diode, and a filter. From this point, if you need to go from say 5V to 3V, then there are simple LDO ICs which will get you there quickly at the cost of some wasted power, but this would not be unique to a AC system either. Presumably DC power distribution systems would still use these components.
Additionally, there are sound cards that are used as inputs into the computer. For example, one of my hobbies is to record music from my guitars, and I use the computer for capture and editing. Most integrated sound cards can only record one channel at a time which is barely adequate for myself, let alone if you have a multiple piece ensemble that you want to record. Additionally, usually the ADC of these products are much better that what is available on the integrated sound card (less noise, adjustable sample rates, more dynamic range). I recognize this is a niche use, but this is one case where the stock sound card is not sufficient.
If you are thinking in a strictly linear scale, then you are right. However, it covers about 50% of the logarithmic scale. Poor choice of wording on the GP's post, but not necessarily incorrect either.
As a side note, RF signals are usually measured in power, since that give a better idea of what is in the air to be received. The power levels received are dependent on two intertwined quantities; the voltage and the impedance of the receiver. Since impedances can vary from system to system this makes power the norm. The difference in powers able to be received is 10^((113-50)/10) ~= 2e6 of dynamic range. This is a huge difference. It is not unusual for receivers to have this dynamic range. Although, 27 dB is a huge hit to suffer.
I agree with you. My comment was more directed at the idea that antenna design is easy. In general, it is not because of the aforementioned issues from my post. But these are things that would have to be worked out on the system design and not necessarily exclusive to what Apple screwed up.
So what. I have designed patch antennas for 1.8 GHz on FR4. Yes the design equations are plug and chug, but on FR-4, the half wavelength of 2 GHz is still about 3 inches. Do really think that there is a spare 3 inches on the back of the iPhone? BTW, 2 GHz is the highest frequency of GSM phones. Typical frequencies are around 900 MHz, which then would be about twice as big as the dimensions stated. Ideally, Apple would like to use something like a patch antenna, since they can just fab it with the PWB. Because the size is prohibitive for the iPhone's requirements, you need to get clever; probably more so than you would find in the ARRL. Again, they can look in other publications in IEEE, but those will not always be plug and chug. If anything, you will see that they simulated some geometry that has some desirable characteristics. It will then be on you do the modeling and simulation yourself.
Additionally, you hand made your antenna presumably. Apple need to make millions of these antennas. Did you model your antenna for any sort of yield analysis to meet the requirements? I'm again guessing no. Do you think that Apple wants some laborer to tune their antennas for them? Of course not. Variability in antenna elements can have drastic effects on VSWR and Q. It would be the antenna engineers job to take this into account also from the manufacturing tolerances and their effects on the antenna's performance.
Now there is a chance you are trolling, and I realize this, but things around the 1GHz range and above are not easy to design because circuit approximations are generally no longer valid. If you do read the ARRL books, I think that they make a good point of trying to impart this on their readers. Also note how few projects there are that are above VHF in these books even though amateur bands go to 1.3 GHz.
Wow, how little you know. I can trivialize anything too. "How hard is it to make a CPU? It just takes a bit of math and digital guide."
Did anyone at Apple consider the polarization of the waves from the tower? How about the bandwidth? What about the antenna pattern? Did they account for near-field interference, which I am sure they will have in such a tiny package, or a hand on the phone for example. How about the antenna gain?
BTW, the math to design antennas is not trivial. Look for Maxwell's equations on wikipedia. These are coupled partial differential equations that cannot be computed in closed form. Usually a SW tool that will do finite element method or method of moment computations to just design this thing. Even then, the simulation will not always reflect the reality of what you modeled. You're not just going to apply some simple math and an RF guide. You want someone who knows what to look for when doing this.
I actually know the author and I know how he came across the Bridgeport and test equipment. First, I will say that he did his PhD work at Michigan State, not at MIT. He does work for MIT Lincoln Labs, hence the MIT moniker everywhere. He acquired his test equipment usually from things like the Dayton Hamvention. I even picked up an oscilloscope myself there for about $50 when I went with him one year. As for the Bridgeport, he know of a machine shop that was getting rid of two Bridgeports. I think he offered them a small sum of money as long as he came to haul them away. Him and and another friend of mine then became owners of their very own milling machines.
However, I will admit that this is certainly beyond the capabilities of most people due to the lack test equipment that is needed to even test the parts found at the swap meat.
You're right. I know the author of the slides. This was part of his PhD disertation. He graduated about 2-3 years ago. He just recently posted the "how to" on his blogspot page this week.
Good points. I am not an IC designer, so I am not sure of the exact implementation or best practices at the die level. My background is in electromagnetics and RF design, but I guess I know enough from those fields to think that similar design practices would still be good.
Correct, I was referring to power consumption. At the die level, you can make a buffer a simple transistor/FET, so the time delay added would be pretty small. The noise that I was referring to in getting from A to B is mostly an EMI sort of issues. In a trace that runs from chip to chip, depending on how long it is, is susceptible to picking up EM radiation from other sources to the point where the EMI would corrupt the received signal to possible give the wrong value (p(0|1) or p(1|0) condition). There are other various mechanisms that cause this error as well such as cross talk, ground bounce, mismatched line impedance. To reduce some of these effects, increasing the line voltage will increase the noise margin at the receiver. As an unwanted side effect, causing this line to have a larger voltage swing (and usually current swing) will now make this a radiator and contribute to the noise environment.
Electrons will drift( look up 'electron mobility' on Wikipedia), but the GP is right in that it is the wave motion of the potentials that are primarily the means in which the information will travel. At the same time, he is just being a bit nit picky. I think what person in the article is trying to say that usually to go from one chip to another, you usually need to provide a buffer (ie amplifier) on the output interface. This will give you better noise margins on the receiver chip. This would be your classical communication theory dilemma; if I sent a one, what is probability that a one was received? Adding a buffer effectively increases the SNR so that the probability of receiving the voltage level that is sent is pretty near 1 (values of 0.99999 are minimally acceptable). Adding buffers will increase the power of the chip.
You have just mirrored my own experience with housing. I moved to Chicagoland in 2005 after I graduated. At the time, a 2 bdrm condo in the suburbs was going for $200k easily and going up at about 5% per year. I thought to myself also that wages are only going up at about 3% at best, so how were people affording this? Because of this, I figured I would just wait this out until some sanity returns. In the mean time while I rented an apartment, some of my co-workers bought into the hype and bought well into the bubble. I don't think prices in Chicago dropped as much as some places, but there are still plenty of foreclosures and short sells around here. To this day I still have not bought since I knew that there is a very good chance that I would be moving after my wife finishes her PhD, but when I am able I will not need to try and sell a condo that I would have been underwater on and instead will have a nice juicy down payment on a single family home.
But then no one likes a braggart, so I try not to rub in the face of my co-workers but on the inside I am laughing.
May be you are reading more into my comment, or I wasn't explicit enough. In any case, here is my chance to better explain what I was trying to say.
If every Israeli (my premise that I still have not verified) is required to serve in the military, and they choose randomly from this pool of people, then realistically they would have a good sample population to test from that would eliminate potential selection bias such as socio-economic factors, education, etc.
As an example of a potential bias, I live in the Chicago area, and I occasionally ride on the subway (once every two months or so). Inside each subway car there are ads, some of which state that some university is doing a study on X. They then are putting out a call for people with X to participate in a study. If I did not ride the subway, then there is a good chance that I would have never seen the sign. Is it then possible that this study could be skewed by the fact that only people who have ridden public transportation and have seen the sign? Is there a hidden correlation between people who ride public transportation and those that have X, because maybe there are people that have X and do not ride public transportation? These factors are placing a sort of filter on the participants, and thus the experiment may not have a true representative sample of the population.
If memory serves me right, military service is mandatory for Israelis. You could probably then assume that they had a good representative sample of the population.
As someone from the US who has visited England (London, Liverpool, Swinden, Cambridge) a couple times in the last few years, I would concur with you. I think I may have gotten a little whiplash while over there when seeing all of the local women. But you may be on to something when you say you develop a taste for the local style. I think part of the attraction for me is that it was different. Plus, in general, I would think that people in the UK and Europe as a whole tend to dress nicer than in the US which certainly makes people watching more enjoyable.
I found that you can use the page up/down keys to tilt the camera to your liking. As a whole, I think they could have done a better job with the camera as well though.
Good point. The original point of my idea was that if someone or some entity, like the NRA for example, was to donate money to a candidate then their opponents would also get the same amount of money to support whatever their agenda is which may be in favor of more gun control. There would be nothing to stop the NRA from running their own ads to support one candidate while trading some other political favors from that candidate. However, if there is more choice from other parties (such as the green party or libertarian party) I would think this would be a very risky proposition from the NRA's perspective if they only had a 1 in 4 chance of having their candidate win.
The ultimate goal of my proposition would be to get more parties involved to represent more views. My current ideology is fiscally conservative, but socially liberal. Neither republicans nor democrats have that ideology, but they are the only ones who ever win. Hopefully another outcome of this would be for the politicians that we do have would be more honest, since they would not have as much personal financial incentive to work these back room deals, a la Illinois's ex-governor Blagojevich and the whole filling Obama's senate seat fiasco.
Thanks for humoring me with my idea. There would still need some more detail ironed out before it could be feasible, but this a 'rough draft' of an idea.
Suppose I donated one dollar in the last election. Then fifty cents would have gone to Barrak Obama, and fifty cents would have gone to John McCain assuming only 2 candidates. I know there were more but I am just making the math simple. If anything, this could also help break the 2 party system we currently have by giving more voice power to parties such as the libertarian and green parties.
Then let me throw one at you to see how you would get around it:
One idea that I have heard is to not necessarily limit the amount of money that any person/corporation could give. However whatever money is donated is added to a public pool for every candidate to receive an equal portion of this pool for re-election purposes.
I would think also necessary here is to make it illegal for any candidate to use any money other than those funds given to them from this fund. This would require the candidate to keep good financial record of the election activities*, and that if it is found that they have questionable accounting practices, then either fine them and/or send them to jail depending on the severity of their bad accounting. Only those candidates that were able to spend less than the money allotted them would be eligible for election.
This may seem harsh, but look at the lot of criminals that are already there. I think the key to any congressional reform is to remove any temptation of easy money from external sources, such as campaign contributions to any specific candidate. I think that if you get rid of this, then I would hope that congress would be more concerned about the people and their rulings. This would be their motivation for re-election. If they can make the majority of their districts happy, this would be their political capital for their re-election.
* If anything, this should be a prerequisite, since the curent congress can't seem to follow a budget. Consider it on the job training for when they are elected to do one of the jobs called out for them in the constitution.
Interesting response. Not trying to troll here. My wife is a scientist, so she has partially warped my mind to think like this. You realize that you yourself have made a generalization that on the surface seems quite plausible. Do you have any direct proof in support of your hypothesis, which I will assume is "Essentially man is a social animal and has an inbuilt desire to fit in with the society that surrounds him/her" Have you found any quotable research showing that your hypothesis has already been proven?
My point here is that until you actually do the research, you can generalize all you want, but that doesn't make it right. Everyone has some sort of anecdotal evidence which could seem to invalidate some research, but does that evidence fall outside of 3 standard deviations for example? Does your anecdotal evidence even have any relation to the original experiment
I am reminded of a recent Daily Show where John Oliver interviewed two different scientists about which primates humans most resemble. (I would link to this, but I am at work and can't get to comedy central). One scientist was arguing that humans were more closely related to Orangutans whereas the other scientist was going with the generally accepted Chimpanzee relationship. John Oliver was trying to get the 'Chimp' scientist to put down the other scientist's research with a 'yo momma' joke. John Oliver Gave the lead in "Yo research is so whack...". The 'Chimp' scientist said, "that it fails to verify the hypothesis".
This is a long way of saying that science is done to find things that seem possibly painfully obvious, and to validate it through experimentation.
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The reason that bit bit depth is proportional to dynamic range would require understanding about how A/D's work. If you have only 8 bits that runs at a supply voltage of 1 volt, then the smallest voltage change able to detected at the one bit level would be only 1/256 = 3.922 mV (or converting to dB -48.13 dB). Compare that to a 16 bits and you get a resolution of 1/16^2 = 15.26 uV or -96.33 dB. When the music get quite enough, say the change is at 2 mV from one point in time to another. The 8 bit A/D will not be able to perceive the change, but the second A/D will be able. To say that an 8 bit A/D can give you 140 dB of dynamic range is just wrong. Even a 16 bit A/D cannot give you 140 dB of dynamic range.
All of this is discounting the effects of noise which will reduce the effective dynamic range also of the A/D. The term here to look for is called ENOB (or effective number of bits).
I think what you are trying to explain is that given the 8 bit A/D, you have to choose where you want your "sweet spot" to be, because in reality you will be capturing something which has a larger dynamic range than what you can capture. Since you only ~48 dB of dynamic range, If you choose an extreme such that the loudest level you can hear can be recorded without saturating your receiver which leads to distortion, then you will not be able to hear the quiet sounds. Conversely, if you decide you want to hear the quietest sounds, then you will saturate your receiver and the sound will be distorted.
You say to provide a source, but this just fundamental receiver design principles, and by receiver I mean RF, Audio, and Video. You can probably find the most on this topic from an RF perspective.
Actually, after a bit of searching, here is a link http://en.wikipedia.org/wiki/Dynamic_range
It's funny you mention the "Everyday Math". I live in the Chicago suburbs, so it seems every person I know that has a kid in grade school in the area is using this series of books for math. I have gone over my sisters house and there have been times where I have been asked to help my niece with her homework because my sister didn't know how to solve the problem since it is so different than how we were taught. Since I have a MSEE and have taken just a few math classes, and even I have to think about how to explain it to here without going over her head. So my first response is to ask where is the text book. I figure this is a good start to see what has been covered so far. She is unable to provide one, because it seems that everything is a worksheet.
I still remember the problem. It goes something like this: "People are on the phone in the US for a total of 123 billion minutes each day. If there are 200 million people with phones, what is the average amount of time each person is on the phone". I am sure for you and I this is a trivial problem, but here is what I have issue with it. First, I asked my niece if she knew what an average was. She said no. Ok, not a big deal so I tried to explain to her what an average was. My second issue with the problem was found out from trying to help her again. I asked her if she knew what factoring was. A blank stare is all I received for that. I didn't even bother asking about scientific notation*. So that leaves the only practical way to solve this is with long division, which I don't necessarily think that is wrong but to me detracts from what they might actually be trying to teach.
So that leads me to my issue with this problem and with "Everyday Math" in general. What is that they are trying to teach in this problem? Is it to explain the concept of an average? Is it how to do tedious long division? I can understand wanting to cross apply different math techniques to solving problems, but if neither concept has been taught then is either concept really being taught by the cross application? If anything, my impression from Everyday Math based on what I have seen is a removal of formalism to math. I know, how boring is it to talk about the associative property or commutative property, but if you have those tools under your belt then everyone is speaking the same language when it comes to math. And given that, then I think I could have helped her to solve this problem in a more algorithmic way. The idea of an average on the other hand needs to be taught in a different way than in just a word problem for kids her age (btw, she is now is 6th grade). Something as easy as rolling a die 10 times and summing the value and dividing by the total number of rolls. Or measuring the height of all the kids in class to find the average, and so on.
Now back to other issue of bad teachers. I would love to be a teacher of either math or physics, but guess what? They won't pay me as well to be a teacher as I can make being an engineer. Not that it is all about the money, but it certainly is an important factor especially when I can pull in twice what an average teacher makes. Since schools are so heavily unionized (at in Chicagoland) there is no way the union would allow disparate rate for math or physics teachers than the others. I think if you fix this problem, then I think there will be better recruiting of good teachers.
*Now I know this is slashdot, so I expect some snarky comments about her maybe not being that good in math. That's fair, but I know that on her report card she had a B+ in math recently, so that would put her at above average in the class. Then again, this could be a whole other discussion on grade inflation in the US.
Mod this up. I was in the Navy for 6 years. I also took advantage of the GI bill and went to a large state university when I left the military. Talk about some of the best times ever. in addition to being able to appreciated the education that you are being given (paying for it yourself also is a good motivator for that), I found it very relaxing compared to the military and a good transition back to civilian life.
One big reason that AC is used by power companies is the ease of transport. In electrical systems, power is lost in the form of R*I*I. Since the copper will always have some trace amounts of resistance, the power loss will go up with current squared. The main advantage that AC has over DC is the ease of which you can switch from one voltage to another. In theory, higher voltages will allow for less current for the same amount of power delivered. For AC, it is just a matter of using a transformer, which is completely passive and can handle large amounts of power. If you were to transmit DC, you would need something a lot more complex to get the voltage to a suitable level. One method would be a DC-DC or DC-AC motor. Another means would be a static inverter to go to AC or use a switch mode power supply to get to DC. However, this doesn't avoid the fact that they are more expensive when compared to a transformer.
Additionally, consumer electronics all have varying voltage requirements internal to their systems. A transformer scales well in size, so to then get to DC, transform the voltage to slightly higher from where you want the DC, use 4 (or 2) diodes for rectification, possibly a zener diode, and a filter. From this point, if you need to go from say 5V to 3V, then there are simple LDO ICs which will get you there quickly at the cost of some wasted power, but this would not be unique to a AC system either. Presumably DC power distribution systems would still use these components.
Additionally, there are sound cards that are used as inputs into the computer. For example, one of my hobbies is to record music from my guitars, and I use the computer for capture and editing. Most integrated sound cards can only record one channel at a time which is barely adequate for myself, let alone if you have a multiple piece ensemble that you want to record. Additionally, usually the ADC of these products are much better that what is available on the integrated sound card (less noise, adjustable sample rates, more dynamic range). I recognize this is a niche use, but this is one case where the stock sound card is not sufficient.
General Turgidson: " Mr President! We must not allow a monkey soldier gap."
If you are thinking in a strictly linear scale, then you are right. However, it covers about 50% of the logarithmic scale. Poor choice of wording on the GP's post, but not necessarily incorrect either.
As a side note, RF signals are usually measured in power, since that give a better idea of what is in the air to be received. The power levels received are dependent on two intertwined quantities; the voltage and the impedance of the receiver. Since impedances can vary from system to system this makes power the norm. The difference in powers able to be received is 10^((113-50)/10) ~= 2e6 of dynamic range. This is a huge difference. It is not unusual for receivers to have this dynamic range. Although, 27 dB is a huge hit to suffer.
Wow....you really are a troll. After reading some of your previous posts, you do nothing but instigate. Good bye troll.
I agree with you. My comment was more directed at the idea that antenna design is easy. In general, it is not because of the aforementioned issues from my post. But these are things that would have to be worked out on the system design and not necessarily exclusive to what Apple screwed up.
So what. I have designed patch antennas for 1.8 GHz on FR4. Yes the design equations are plug and chug, but on FR-4, the half wavelength of 2 GHz is still about 3 inches. Do really think that there is a spare 3 inches on the back of the iPhone? BTW, 2 GHz is the highest frequency of GSM phones. Typical frequencies are around 900 MHz, which then would be about twice as big as the dimensions stated. Ideally, Apple would like to use something like a patch antenna, since they can just fab it with the PWB. Because the size is prohibitive for the iPhone's requirements, you need to get clever; probably more so than you would find in the ARRL. Again, they can look in other publications in IEEE, but those will not always be plug and chug. If anything, you will see that they simulated some geometry that has some desirable characteristics. It will then be on you do the modeling and simulation yourself.
Additionally, you hand made your antenna presumably. Apple need to make millions of these antennas. Did you model your antenna for any sort of yield analysis to meet the requirements? I'm again guessing no. Do you think that Apple wants some laborer to tune their antennas for them? Of course not. Variability in antenna elements can have drastic effects on VSWR and Q. It would be the antenna engineers job to take this into account also from the manufacturing tolerances and their effects on the antenna's performance.
Now there is a chance you are trolling, and I realize this, but things around the 1GHz range and above are not easy to design because circuit approximations are generally no longer valid. If you do read the ARRL books, I think that they make a good point of trying to impart this on their readers. Also note how few projects there are that are above VHF in these books even though amateur bands go to 1.3 GHz.
Wow, how little you know. I can trivialize anything too. "How hard is it to make a CPU? It just takes a bit of math and digital guide."
Did anyone at Apple consider the polarization of the waves from the tower? How about the bandwidth? What about the antenna pattern? Did they account for near-field interference, which I am sure they will have in such a tiny package, or a hand on the phone for example. How about the antenna gain?
BTW, the math to design antennas is not trivial. Look for Maxwell's equations on wikipedia. These are coupled partial differential equations that cannot be computed in closed form. Usually a SW tool that will do finite element method or method of moment computations to just design this thing. Even then, the simulation will not always reflect the reality of what you modeled. You're not just going to apply some simple math and an RF guide. You want someone who knows what to look for when doing this.
I actually know the author and I know how he came across the Bridgeport and test equipment. First, I will say that he did his PhD work at Michigan State, not at MIT. He does work for MIT Lincoln Labs, hence the MIT moniker everywhere. He acquired his test equipment usually from things like the Dayton Hamvention. I even picked up an oscilloscope myself there for about $50 when I went with him one year. As for the Bridgeport, he know of a machine shop that was getting rid of two Bridgeports. I think he offered them a small sum of money as long as he came to haul them away. Him and and another friend of mine then became owners of their very own milling machines.
However, I will admit that this is certainly beyond the capabilities of most people due to the lack test equipment that is needed to even test the parts found at the swap meat.
You're right. I know the author of the slides. This was part of his PhD disertation. He graduated about 2-3 years ago. He just recently posted the "how to" on his blogspot page this week.
Good points. I am not an IC designer, so I am not sure of the exact implementation or best practices at the die level. My background is in electromagnetics and RF design, but I guess I know enough from those fields to think that similar design practices would still be good.
Correct, I was referring to power consumption. At the die level, you can make a buffer a simple transistor/FET, so the time delay added would be pretty small. The noise that I was referring to in getting from A to B is mostly an EMI sort of issues. In a trace that runs from chip to chip, depending on how long it is, is susceptible to picking up EM radiation from other sources to the point where the EMI would corrupt the received signal to possible give the wrong value (p(0|1) or p(1|0) condition). There are other various mechanisms that cause this error as well such as cross talk, ground bounce, mismatched line impedance. To reduce some of these effects, increasing the line voltage will increase the noise margin at the receiver. As an unwanted side effect, causing this line to have a larger voltage swing (and usually current swing) will now make this a radiator and contribute to the noise environment.
I hope I understood what you were asking.
Electrons will drift( look up 'electron mobility' on Wikipedia), but the GP is right in that it is the wave motion of the potentials that are primarily the means in which the information will travel. At the same time, he is just being a bit nit picky. I think what person in the article is trying to say that usually to go from one chip to another, you usually need to provide a buffer (ie amplifier) on the output interface. This will give you better noise margins on the receiver chip. This would be your classical communication theory dilemma; if I sent a one, what is probability that a one was received? Adding a buffer effectively increases the SNR so that the probability of receiving the voltage level that is sent is pretty near 1 (values of 0.99999 are minimally acceptable). Adding buffers will increase the power of the chip.
You have just mirrored my own experience with housing. I moved to Chicagoland in 2005 after I graduated. At the time, a 2 bdrm condo in the suburbs was going for $200k easily and going up at about 5% per year. I thought to myself also that wages are only going up at about 3% at best, so how were people affording this? Because of this, I figured I would just wait this out until some sanity returns. In the mean time while I rented an apartment, some of my co-workers bought into the hype and bought well into the bubble. I don't think prices in Chicago dropped as much as some places, but there are still plenty of foreclosures and short sells around here. To this day I still have not bought since I knew that there is a very good chance that I would be moving after my wife finishes her PhD, but when I am able I will not need to try and sell a condo that I would have been underwater on and instead will have a nice juicy down payment on a single family home.
But then no one likes a braggart, so I try not to rub in the face of my co-workers but on the inside I am laughing.
May be you are reading more into my comment, or I wasn't explicit enough. In any case, here is my chance to better explain what I was trying to say.
If every Israeli (my premise that I still have not verified) is required to serve in the military, and they choose randomly from this pool of people, then realistically they would have a good sample population to test from that would eliminate potential selection bias such as socio-economic factors, education, etc.
As an example of a potential bias, I live in the Chicago area, and I occasionally ride on the subway (once every two months or so). Inside each subway car there are ads, some of which state that some university is doing a study on X. They then are putting out a call for people with X to participate in a study. If I did not ride the subway, then there is a good chance that I would have never seen the sign. Is it then possible that this study could be skewed by the fact that only people who have ridden public transportation and have seen the sign? Is there a hidden correlation between people who ride public transportation and those that have X, because maybe there are people that have X and do not ride public transportation? These factors are placing a sort of filter on the participants, and thus the experiment may not have a true representative sample of the population.
If memory serves me right, military service is mandatory for Israelis. You could probably then assume that they had a good representative sample of the population.
As someone from the US who has visited England (London, Liverpool, Swinden, Cambridge) a couple times in the last few years, I would concur with you. I think I may have gotten a little whiplash while over there when seeing all of the local women. But you may be on to something when you say you develop a taste for the local style. I think part of the attraction for me is that it was different. Plus, in general, I would think that people in the UK and Europe as a whole tend to dress nicer than in the US which certainly makes people watching more enjoyable.
I found that you can use the page up/down keys to tilt the camera to your liking. As a whole, I think they could have done a better job with the camera as well though.
Good point. The original point of my idea was that if someone or some entity, like the NRA for example, was to donate money to a candidate then their opponents would also get the same amount of money to support whatever their agenda is which may be in favor of more gun control. There would be nothing to stop the NRA from running their own ads to support one candidate while trading some other political favors from that candidate. However, if there is more choice from other parties (such as the green party or libertarian party) I would think this would be a very risky proposition from the NRA's perspective if they only had a 1 in 4 chance of having their candidate win.
The ultimate goal of my proposition would be to get more parties involved to represent more views. My current ideology is fiscally conservative, but socially liberal. Neither republicans nor democrats have that ideology, but they are the only ones who ever win. Hopefully another outcome of this would be for the politicians that we do have would be more honest, since they would not have as much personal financial incentive to work these back room deals, a la Illinois's ex-governor Blagojevich and the whole filling Obama's senate seat fiasco.
Thanks for humoring me with my idea. There would still need some more detail ironed out before it could be feasible, but this a 'rough draft' of an idea.
Suppose I donated one dollar in the last election. Then fifty cents would have gone to Barrak Obama, and fifty cents would have gone to John McCain assuming only 2 candidates. I know there were more but I am just making the math simple. If anything, this could also help break the 2 party system we currently have by giving more voice power to parties such as the libertarian and green parties.
Then let me throw one at you to see how you would get around it:
One idea that I have heard is to not necessarily limit the amount of money that any person/corporation could give. However whatever money is donated is added to a public pool for every candidate to receive an equal portion of this pool for re-election purposes.
I would think also necessary here is to make it illegal for any candidate to use any money other than those funds given to them from this fund. This would require the candidate to keep good financial record of the election activities*, and that if it is found that they have questionable accounting practices, then either fine them and/or send them to jail depending on the severity of their bad accounting. Only those candidates that were able to spend less than the money allotted them would be eligible for election.
This may seem harsh, but look at the lot of criminals that are already there. I think the key to any congressional reform is to remove any temptation of easy money from external sources, such as campaign contributions to any specific candidate. I think that if you get rid of this, then I would hope that congress would be more concerned about the people and their rulings. This would be their motivation for re-election. If they can make the majority of their districts happy, this would be their political capital for their re-election.
* If anything, this should be a prerequisite, since the curent congress can't seem to follow a budget. Consider it on the job training for when they are elected to do one of the jobs called out for them in the constitution.
Interesting response. Not trying to troll here. My wife is a scientist, so she has partially warped my mind to think like this. You realize that you yourself have made a generalization that on the surface seems quite plausible. Do you have any direct proof in support of your hypothesis, which I will assume is "Essentially man is a social animal and has an inbuilt desire to fit in with the society that surrounds him/her" Have you found any quotable research showing that your hypothesis has already been proven?
My point here is that until you actually do the research, you can generalize all you want, but that doesn't make it right. Everyone has some sort of anecdotal evidence which could seem to invalidate some research, but does that evidence fall outside of 3 standard deviations for example? Does your anecdotal evidence even have any relation to the original experiment
I am reminded of a recent Daily Show where John Oliver interviewed two different scientists about which primates humans most resemble. (I would link to this, but I am at work and can't get to comedy central). One scientist was arguing that humans were more closely related to Orangutans whereas the other scientist was going with the generally accepted Chimpanzee relationship. John Oliver was trying to get the 'Chimp' scientist to put down the other scientist's research with a 'yo momma' joke. John Oliver Gave the lead in "Yo research is so whack...". The 'Chimp' scientist said, "that it fails to verify the hypothesis".
This is a long way of saying that science is done to find things that seem possibly painfully obvious, and to validate it through experimentation.