The point I was trying to make was that there is nothing magic about 2.4 GHz. RF works pretty well at heating things at many different frequencies. The article I did point to mentioned that 2.4 GHz is far below any resonance for water- the first resonance of water (vapor) is at about 22 GHz. There are industrial RF heating ovens that use 900 MHz. If you want to avoid RF heating of your head, you have to keep virtually any device that generates RF away from it. On the other hand, these devices are very limited in power, so the actual heating that they do is minimal.
I did a bit of research on the damage that RF can do to living tissue, and the only verifiable damaging effect is localized heating, and that is a factor of average power that hits the tissue. (I was working with a high peak power radar at the time, and very concerned.)
There are other reasons for 2.45 GHz beyond communications- the magnetron for it is a comfortable size, not too big to fit in a household device, not too small as to be hard to manufacture.
That frequency *was* in use, just not by many commercial devices- it is at the high end of L-Band, which was used in the 70's for radar (for sure) and satellite communication (I think).
While the carpet is conductive, which would dissipate static electricity, the most important reason for this shielding is to make the place as RF tight as possible, which the carpet also helps to do. That place is one huge "SKIFF" (Secure information processing facility). Ok, I'm not exactly sure how to spell the acronym, I just remember it spoken. Hard for RF to get out, but also hard for it to get in.
They were doing satellite eavesdropping, so they want to eliminate as much interference to their dishes as possible. Location gave them isolation from external sources, they just have to make sure that their own computers and whatnot don't kill the RF quiet that they worked so hard to create.
They will avoid 2.4 GHz, not because of the resonant frequency of water (Which it is NOT, check this link). When the frequency was chosen for microwave ovens, they chose 2.45 GHz because they knew that it would interfere with other forms of communication, and they wanted to keep the interferers all in one (relatively unused at the time) place. Enough RF at virtually any frequency will heat things.
There are other frequencies used for heating things, they are in what is called ISM (Industrial, Scientific, Medical) bands. These bands are a bit more "anything goes" than other frequencies. The FCC rules are in this hefty tome. I'll leave it up to you to find the applicable parts. That's why Bluetooth and 802.11 work in the 2.4 GHz region. They have more free reign for what you can do, but you also have to accept interference without complaint.
If your resturant/store/whatever happens to be built with enough electo-magnetic sheilding that cellular devices can't effectively communicate within your establishment, I think you'd be in the clear.
Absolutely, shielding would be *very* expensive, and quite high maintainence. You would either need an "air-lock" style door, or a serpentine with RF-absorbent materials (the materials are very expensive, and it takes a lot of square footage). I saw a serpentine at a secure facility I visited once. They didn't want the airlock doors since the shielding used to seal those doesn't last too many cycles. For a truly RF tight facility, you also have to shield your power going in and out, and any sort of communication lines, because they can sometimes act as passive radiators. Just putting aluminum screens over the windows isn't enough. As you go up in frequency, the quality of the shielding has to go up- meaning smaller holes for the rf to go in and out. It would probably be cheaper just to hire a door-man that would frisk anyone that enters.
My calling them buzzwords apply to the context in which they are used, and in this case, it applies to a website that is doing little more than quoting words that investors want to see, without providing any substance. To quote Merriam-Webster:
Buzzword: an important-sounding usually technical word or phrase often of little meaning used chiefly to impress laymen.
Using the term "synthetic aperture" and "Maser" without providing any real explanation seems more of an attempt to obfuscate and redirect the reader away from trying to understand their technology than provide information. This fully fits into the definiton of buzzword.
I know what a MASER is and what Synthetic Aperture is. You are mistaken about synthetic aperture, though. It is *NOT* a type of radar. It is a method of effectively creating a very large antenna by using a small antenna and motion of the antenna or target. It is generally used for radar. But the term only applies to a method of increasing gain and resolution. (I designed, built and operated experimental synthetic aperture radars for 6 years, so I have a bit of experience in this area.) It is not just an alternate way of using any standard radar, it is vastly different. It has its own advantages (when focused properly, high resolution independent of range, limited solely by noise) and limitations (like they can't provide an image in real time, and moving targets screw them up big time). I have no idea about what these guys are really doing, but it is more likely that they are using a phased array type of system, if they are actually using multiple antennas to provide gain.
Has anyone come up with a personal anti-cell phone device?
In the US, use or sale of these would be illegal. The FCC specifically bars devices that intentionally cause interference. Owning, manufacturing, marketing, offering for sale or operating a cell phone jammer is punishable by an $11,000 fine and up to a year in prison for each offense.
The laws relating to this vary as you move around the world. There are companies in England, Japan, Taiwan, and Israel that manufacture jammers. This Link should tell you more. According to this article, Hubgiant of Taipei, Taiwan sells a personal Cellular telephone jammer. There are others around, but I'm sure that there are plenty of scams for them out there- if you get a "illegal" jammer in the US, and it doesn't work, who are you going to complain to?
It's posted below, but I have to re-iterate, Empire was the most addictive game I can remember. I ran the single player version on a VAX 11/780 at work, and dialed in on an 1200 baud modem with a dumb terminal to play it at home. It was very playable at 1200 baud. Included on many of the DECUS tapes. Simple text display/ interface, and it would seem like forever when the computer would take its turn, especially getting near to the end of the game, when there was a lot of enemy left. I was able to find a version I could run on a PC (8088), but it was never the same.
Give me a nice simple interface, that's playable without having to remember too many keystrokes... that's where I can get sucked in really easy.
Wolfenstien 3D and Doom were much the same for me, I got addicted quickly, but I was able to kick the habit eventually. The 2nd game I've ever played in a genre is never quite the same- I lose some of the wonder at the great artifical world that's been created for me.
I thought they already did, what was all that news about a while back?
They removed the "SA" or selective availability coding on the C/A code. The SA code was the intentional in-accuracy in the GPS clocks that made the C/A position solutions less accurate. Without SA, GPS is much more accurate than it was, but still nowhere near the level of P (Precise) code (which is inherently 10 times more accurate, since it has 10 times more bandwidth) There are a bunch of different ways to make GPS more accurate, like looking at the phase of the incoming signal, or using differential, or just averaging, though differential or averaging don't work as well when the reciever is moving at satellite speeds.
The really accurate GPS requires the use of both GPS signals- commercial handheld recievers use just the C/A (Coarse acquisition) code, which was there just to give an approximate fix to feed to the P(Y) code engine, which is where the true military accuracy comes from. I suspect that these satellites use the encrypted P code (the Y code) that is reserved for government use. This must be a non-run of the mill receiver, since commercial recievers have altitude and velocity restrictions (50,000 ft and 999 mph, I think, but I'm not really sure at all). Since they have gone to all that effort, I'm sure they took the extra care to get a full military grade, dual channel, P code receiver.
Your normal handheld receiver uses the C/A code, which only uses 1 MHz of bandwidth, which limits the possible accuracy of the position solution. the P(Y) code is 10 MHz wide, and broadcast on two different frequencies. I don't think that the technology used in these satellites will have much effect on commercial receivers, until the DOD removes the encryption on GPS, which they are *very* adamant about not doing.
I looked over the scant information found on their website, and what I don't understand is how they are going against Maxwell's equations. I don't really get the whole just sending a magnetic field down a wire- since we don't have a source of magnetic monopoles, all magnetic fields are generated by the motion of an electric charge. No current flow- no magnetic field, and therefore, no data.
They use a bunch of buzzwords, like "maser" and "synthetic aperture", but no real information. I won't trust it until I see it.
Frequent breaks are really important- staring at something that is a fixed distance away for a long time is something your eyes aren't really suited for. Take a break, find a window and look at a distant object- give your eyes a chance to focus at a variety of distances. I find these breaks also help in my problem solving and general stress level.
The company I used to work for, Andrew Corporation, produced an active transponder that was aimed at improving cellular telephone reception in buildings- it was a panel you placed in a window and had flat antennas on each side. We had an experimental version in our office (our group didn't make these things). You can't just place two antennas with an amplifier between them because amplifiers only go one way, and if you have a return path really close, it is highly likely that they will oscillate.
I have seen passive re-radiators- essentially just a pair of antennas with a cable in between- which might help, but you need to get some pretty high quality cable between the antennas, because the cable losses at the PCS frequencies (up near 2 GHz are pretty high). (I'm guessing this is a PCS or some other non-traditional-cellular (800-900 MHz) cellular phone, since building construction is much less friendly to letting the PCS frequencies through).
For a passive re-radiator to work well, you need to place an antenna outside (not behinid a window- many windows have metallic coatings that will kill RF), preferably in full view of your local cellular phone tower. Run the absolutely shortest cable you can to your inside antenna. Both antennas must be tuned to the frequency of interest. Unfortunately, since celluar phones are frequency agile or spread spectrum, you want antennas that have a somewhat wide band around the frequency band- don't forget that transmit and recieve from the tower may be on separate frequency bands.
-OR- work hard and get a window office. This is probably the most effective solution to your problem.
With all sorts of cheap electronic gadgets available, there isn't the same incentive to play around with electronics as there has been in the past. Who needs to build a shortwave radio to find people to talk to, when the Internet has made long distance chatting trivialy easy?
Work the other interests into it. If the child reads about Tesla... build a Tesla Coil. (I guess that would need some pretty good adult supervision, too).
What you can do is find things that interest the child and see how you can work electronics into it. If they are already into computers and basic programming, microcontrollers are a good start (and a personal favorite of mine) They can teach about the basics of computers without becoming overwhelming- the Microchip PIC series, especially the 16F84 is a good choice, relatively cheap, can be programmed with *really* cheap hardware, and the development tools from Microchip are free. You as the instructor must become proficient in them first, to not add to the frustration of your student. Blinking LEDs can be an introduction to the wide world of electronics- because once they know they can do it, they will be primed to learn more. There are a number of other microcontrollers that have even simpler programming interfaces than Microchip's- such as a Basic Stamp from Parallax.
To really keep their interest, you need to have payoff early- they need to see that they can do neat stuff before the theory gets pounded into them. Thankfully, with digital electronics, you don't have to worry as much about currents and Ohm's law to get results. The math will come, but it doesn't have to be the first part. They will be much more interested in learning why something works, after seeing it work, but you have to do both- a lot of the kits that you can find just show how to build it- without giving any insight into why it works. The why may be up to you. It will require work and commitment on both the teacher's part and the student's part.
I lived in Maryland when they made us start dialing area codes for the local calls in the DC suburbs- it used to be that I just had to dial a 7 digit number from the DC suburbs of Maryland (301) and get to Virginia (703) and DC (202). They started running out of prefixes, since they couldn't duplicate the prefixes within the suburban DC area. So we had to start dialing area codes to get to Virginia and DC. There was a huge uproar over that. You would have figured that life as we know it was going to cease to exist. It didn't, the phones kept ringing. Then they went to an overlay (multiple area codes covering the same area) and there was another uproar. It happened, and people got used to it. I moved to central Texas (512), and now I only have to dial 7 digits for a local call. It was a weird transition, but I survived (I can dial the area code first, but it doesn't make a difference). In the numbering plan for the area, we will be going to an overlay soon. And again, we will hear all sorts of uproar.
Big effin deal. People will complain, then they will get used to it. It is a matter of growth and progress. People should be proud of the fact that they need more phone numbers- more people in the area, a larger tax base, people are getting better connected- it really is a good thing! It just shows how wired and high tech your area is.
Physical security is very important- you've got to make sure that the thieves don't walk off with your security system.
Preferably you should have some sort of off-site security storage of those important images. If you've already got a full time link, think about FTP-ing the images to some where else. If someone does break in, you need to keep a copy of that picture on a machine that they can't steal. Unfortunately the images you're going to get with most simple cameras are going to be pretty poor- unless the miscreant puts their face *right in front* of the camera, it will be difficult to positively identify them. Cameras all over the place will probably be more effective as a deterrent. Who says that each one has to be hooked up?
You could also tie this into a pager- but again, you need something that is protected from the thief.
Also, don't forget to increase your vigilance over the coming months, since the thieves know which home they plundered, they also know who's probably going to be getting nice new (replacement) equipment in the near future.
If you think about this device, and what its mission is, it isn't very far off from a cruise missle, except that it doesn't blow itself up when it completes its mission. It comes back to fight another day. Cruise missles suffer from the same vulnerabilites, they've got multiple navigation sources (GPS, inertial, landmarks), and sat. communications, where they can be re-targeted if needed.
The first such mission envisioned is the suppression of enemy air defenses.
I think that this means the ground based, anti-aircraft installations (guns, missles, radar) The airframe is a pretty stealthy design, which is right for going against that sort of target. That type of mission is the most dangerous for a human pilot. I'm sure Congress likes it, since if one of them goes down in combat, they don't have to tell their constituents that they are sending their children to death in some far off country.
I would think air-air combat is a much harder problem, but it would be very good to take the human out of the loop- The plane could then do continuous hi-G turns, both positive and negative, stuff that would knock out a human in seconds.
While the article doesn't come out and say it, I'm guessing there will be serious total bandwidth limitations- since there are no tracking antennas, and since this is referred to as part of a satellite TV service, it must be from (and probably to) a satellite in geosync orbit. All traffic is probably going to just one satellite. Once a lot of people sign up for this- popularity will kill it- since I'm sure that they can sign people up to long term contracts faster than they can put more transponders up.
Plus there is the fact that anything beamed to you is probably also being beamed to everyone in a multiple state area around you. I sure hope they have some *strong* encryption built in. They ought to be doing something better than DES, no?
I hate to say it, but the microsoft backed Teledesic system is a much better system (many satellites in low earth orbit- kinda like a cellular system) the satellites are closer and cover smaller areas, so the amount of bandwidth/satellite is much smaller.
Can't get to the website due to errors over there, but if this kit is based on the BA1404 chip like the Ramsey FM10 (which, for this price I think it has to be) you may have serious problems receiving what this thing puts out on many FM receivers. The BA1404 uses a tank circuit (an inductor and a capacitor) as the part that sets the frequency, and this can drift really badly. Many FM recievers today are PLL based (if it has a digital display, it probably is) and can't tune in an analog sense. If the signal drifts off of the FCC "channel" (they go in 200KHz increments, starting at 87.9 up to 107.9), many receivers won't, and if they do at all you get a really noisy signal. An FM discriminator can pull in a signal a few KHz, but they are generally designed to work within the frequency specification that FM broadcasters are mandated to follow by the FCC, which is *much* smaller than the frequency precision an L-C tank will give you.
There are FM transmitters out there that don't suffer from this problem- they use a crystal controlled PLL circuit to set the frequency, Ramsey sells one. But it is much more complex, and more expensive (I think Ramsey's is about $150)
Is Slashdot really a news source? Merriam-Webster defines news as this: "1 a : a report of recent events b : previously unknown information". I don't think so. There are pointers to news sites and discussion about them, but the news isn't reported here. The editors are not reporting things as fact. Yes, there are features, but they aren't news, usually it is just opinion or some sort of review. Otherwise what we find here are editorials, which again, according to Merriam webster: : "a newspaper or magazine article that gives the opinions of the editors or publishers; also : an expression of opinion that resembles such an article" The operative word there is opinion.
I use slashdot more as a news clipping service- where I can find out about things without having to scan all the news sites myself.
And how are the "real" news sources held accountable anyway? They can be pointed out as "wrong" by their peer journals, or they can be sued in court for libel. Anyone is free to point out something as wrong right here, and nothing prevents prevents anyone here- including the comment posters- from being sued. There is no guarantee that any media is free from bias, and it is pretty fact that the editors of slashdot have biases. Very often those biases match with the readers, so they aren't noted as biases.
Guys give us a break. Tell us if you are running out of topics. We'll do the homework for you. But don't please let every other posting be something of only US interest.
Unfortunately, the US Presidential election is of more than just US interest. What will be determined is who will lead the United States. How much influence the United States has is debatable, but what can't be denied is that the US has international influence. Look some of the mainstays of our vocation/avocation. Intel: based in the USA. Cisco: Based in the USA. Sun: Based in the USA What these companies do extends far beyond the borders of the US. Yes there are some other players, but if you took these away, the high tech world would look very, very, different.
You can stick your head in the sand and act like the US presidential election doesn't matter. Your choice. But the world is a lot like the internet- connected in many different places in many different ways. This election will influence your life. Maybe not as much if you're not in the US, but it will.
He asserts that there are only three (spatial)dimensions. I've been reading _The_Elegant_Universe_ by Brian Greene, which is largely a book on superstring theory, which points to 10 (or 11) dimensions, with the saptial dimensions other than x,y,z (the normal ones we use every day) being very, very small (on the order of the Planck length. While there appears to be no real proof of string theory, it has been shown to be very good at predicting things that can be observed, and provides a unifiying framework for all forces (weak, strong, EM and gravity). But I digress- he asserts that Life could not exist if it were 2 or 4. Why? What connection is there between life and dimensions. Maybe life as we know it, but all our experiences are constrained to our three dimensional (apparent) world. Yes, its true that our 3 dimensional objects don't fit quite right in a 2 or 4 dimensional world, but it doesn't mean they can't.
As to the constants- true, the universe *as we know it* wouldn't exist if they were different, but whos to say that another wouldn't? The values of these constants may not be so precarious- if you place the ball at the very top of a hill, it's in equilibrium, but not stable- some force could easily roll it one way or another, and once it does start to move, it will keep rolling until it (coupled with friction) finds a more stable point- why can't these constants vary like that?
Maybe the big bang is a cyclic process, sometimes it forms a universe that isn't stable, so it just collapses and reforms with a new set of contants. We know about this one because, simply, we're here.
So, when (and where) can I pick up my almost free night vision goggles?
They're already here (kinda). Binoculars (with large lenses) collect more light than the unaided human eye and can serve to amplify the light- you just need to find binoculars that have large lenses and low magnification. This works especially well in low light (dusk, not dark) situations.
from that list there are only 3 (Audiovox PCX1100XL, Nokia 5180, Sanyo SCP-4000) that use analog only
They only listed the analog in their chart, but at the Sanyo SCP-4000 is dual mode (AMPS Analog/PCS digital) for sure- there are two of them in my family.
oh and with the CDMA phones, it only transmits at peak power when you scream into the thing as loud as you can
Nope. The volume you speak at affects the output power not at all. Remember, these are just bits you're transmitting. If you look at it with a spectrum analyzer, the power is always just about equal, though it may go down when you are transmitting "silence" due to the style of codec that the phone employs (the codec acts as a kind of compression scheme for voice). This is more of a battery power saver thing than anything else.
Slashdot Mirror
The point I was trying to make was that there is nothing magic about 2.4 GHz. RF works pretty well at heating things at many different frequencies. The article I did point to mentioned that 2.4 GHz is far below any resonance for water- the first resonance of water (vapor) is at about 22 GHz. There are industrial RF heating ovens that use 900 MHz. If you want to avoid RF heating of your head, you have to keep virtually any device that generates RF away from it. On the other hand, these devices are very limited in power, so the actual heating that they do is minimal.
I did a bit of research on the damage that RF can do to living tissue, and the only verifiable damaging effect is localized heating, and that is a factor of average power that hits the tissue. (I was working with a high peak power radar at the time, and very concerned.)
There are other reasons for 2.45 GHz beyond communications- the magnetron for it is a comfortable size, not too big to fit in a household device, not too small as to be hard to manufacture.
That frequency *was* in use, just not by many commercial devices- it is at the high end of L-Band, which was used in the 70's for radar (for sure) and satellite communication (I think).
They were doing satellite eavesdropping, so they want to eliminate as much interference to their dishes as possible. Location gave them isolation from external sources, they just have to make sure that their own computers and whatnot don't kill the RF quiet that they worked so hard to create.
They will avoid 2.4 GHz, not because of the resonant frequency of water (Which it is NOT, check this link). When the frequency was chosen for microwave ovens, they chose 2.45 GHz because they knew that it would interfere with other forms of communication, and they wanted to keep the interferers all in one (relatively unused at the time) place. Enough RF at virtually any frequency will heat things.
There are other frequencies used for heating things, they are in what is called ISM (Industrial, Scientific, Medical) bands. These bands are a bit more "anything goes" than other frequencies. The FCC rules are in this hefty tome. I'll leave it up to you to find the applicable parts. That's why Bluetooth and 802.11 work in the 2.4 GHz region. They have more free reign for what you can do, but you also have to accept interference without complaint.
If your resturant/store/whatever happens to be built with enough electo-magnetic sheilding that cellular devices can't effectively communicate within your establishment, I think you'd be in the clear.
Absolutely, shielding would be *very* expensive, and quite high maintainence. You would either need an "air-lock" style door, or a serpentine with RF-absorbent materials (the materials are very expensive, and it takes a lot of square footage). I saw a serpentine at a secure facility I visited once. They didn't want the airlock doors since the shielding used to seal those doesn't last too many cycles. For a truly RF tight facility, you also have to shield your power going in and out, and any sort of communication lines, because they can sometimes act as passive radiators. Just putting aluminum screens over the windows isn't enough. As you go up in frequency, the quality of the shielding has to go up- meaning smaller holes for the rf to go in and out. It would probably be cheaper just to hire a door-man that would frisk anyone that enters.
My calling them buzzwords apply to the context in which they are used, and in this case, it applies to a website that is doing little more than quoting words that investors want to see, without providing any substance. To quote Merriam-Webster:
Buzzword: an important-sounding usually technical word or phrase often of little meaning used chiefly to impress laymen.
Using the term "synthetic aperture" and "Maser" without providing any real explanation seems more of an attempt to obfuscate and redirect the reader away from trying to understand their technology than provide information. This fully fits into the definiton of buzzword.
I know what a MASER is and what Synthetic Aperture is. You are mistaken about synthetic aperture, though. It is *NOT* a type of radar. It is a method of effectively creating a very large antenna by using a small antenna and motion of the antenna or target. It is generally used for radar. But the term only applies to a method of increasing gain and resolution. (I designed, built and operated experimental synthetic aperture radars for 6 years, so I have a bit of experience in this area.) It is not just an alternate way of using any standard radar, it is vastly different. It has its own advantages (when focused properly, high resolution independent of range, limited solely by noise) and limitations (like they can't provide an image in real time, and moving targets screw them up big time). I have no idea about what these guys are really doing, but it is more likely that they are using a phased array type of system, if they are actually using multiple antennas to provide gain.
Has anyone come up with a personal anti-cell phone device?
In the US, use or sale of these would be illegal. The FCC specifically bars devices that intentionally cause interference. Owning, manufacturing, marketing, offering for sale or operating a cell phone jammer is punishable by an $11,000 fine and up to a year in prison for each offense.
The laws relating to this vary as you move around the world. There are companies in England, Japan, Taiwan, and Israel that manufacture jammers. This Link should tell you more. According to this article, Hubgiant of Taipei, Taiwan sells a personal Cellular telephone jammer. There are others around, but I'm sure that there are plenty of scams for them out there- if you get a "illegal" jammer in the US, and it doesn't work, who are you going to complain to?
It's posted below, but I have to re-iterate, Empire was the most addictive game I can remember. I ran the single player version on a VAX 11/780 at work, and dialed in on an 1200 baud modem with a dumb terminal to play it at home. It was very playable at 1200 baud. Included on many of the DECUS tapes. Simple text display/ interface, and it would seem like forever when the computer would take its turn, especially getting near to the end of the game, when there was a lot of enemy left. I was able to find a version I could run on a PC (8088), but it was never the same.
Give me a nice simple interface, that's playable without having to remember too many keystrokes... that's where I can get sucked in really easy.
Wolfenstien 3D and Doom were much the same for me, I got addicted quickly, but I was able to kick the habit eventually. The 2nd game I've ever played in a genre is never quite the same- I lose some of the wonder at the great artifical world that's been created for me.
I thought they already did, what was all that news about a while back?
They removed the "SA" or selective availability coding on the C/A code. The SA code was the intentional in-accuracy in the GPS clocks that made the C/A position solutions less accurate. Without SA, GPS is much more accurate than it was, but still nowhere near the level of P (Precise) code (which is inherently 10 times more accurate, since it has 10 times more bandwidth) There are a bunch of different ways to make GPS more accurate, like looking at the phase of the incoming signal, or using differential, or just averaging, though differential or averaging don't work as well when the reciever is moving at satellite speeds.
The really accurate GPS requires the use of both GPS signals- commercial handheld recievers use just the C/A (Coarse acquisition) code, which was there just to give an approximate fix to feed to the P(Y) code engine, which is where the true military accuracy comes from. I suspect that these satellites use the encrypted P code (the Y code) that is reserved for government use. This must be a non-run of the mill receiver, since commercial recievers have altitude and velocity restrictions (50,000 ft and 999 mph, I think, but I'm not really sure at all). Since they have gone to all that effort, I'm sure they took the extra care to get a full military grade, dual channel, P code receiver.
Your normal handheld receiver uses the C/A code, which only uses 1 MHz of bandwidth, which limits the possible accuracy of the position solution. the P(Y) code is 10 MHz wide, and broadcast on two different frequencies. I don't think that the technology used in these satellites will have much effect on commercial receivers, until the DOD removes the encryption on GPS, which they are *very* adamant about not doing.
I looked over the scant information found on their website, and what I don't understand is how they are going against Maxwell's equations. I don't really get the whole just sending a magnetic field down a wire- since we don't have a source of magnetic monopoles, all magnetic fields are generated by the motion of an electric charge. No current flow- no magnetic field, and therefore, no data.
They use a bunch of buzzwords, like "maser" and "synthetic aperture", but no real information. I won't trust it until I see it.
Frequent breaks are really important- staring at something that is a fixed distance away for a long time is something your eyes aren't really suited for. Take a break, find a window and look at a distant object- give your eyes a chance to focus at a variety of distances. I find these breaks also help in my problem solving and general stress level.
The company I used to work for, Andrew Corporation, produced an active transponder that was aimed at improving cellular telephone reception in buildings- it was a panel you placed in a window and had flat antennas on each side. We had an experimental version in our office (our group didn't make these things). You can't just place two antennas with an amplifier between them because amplifiers only go one way, and if you have a return path really close, it is highly likely that they will oscillate.
I have seen passive re-radiators- essentially just a pair of antennas with a cable in between- which might help, but you need to get some pretty high quality cable between the antennas, because the cable losses at the PCS frequencies (up near 2 GHz are pretty high). (I'm guessing this is a PCS or some other non-traditional-cellular (800-900 MHz) cellular phone, since building construction is much less friendly to letting the PCS frequencies through).
For a passive re-radiator to work well, you need to place an antenna outside (not behinid a window- many windows have metallic coatings that will kill RF), preferably in full view of your local cellular phone tower. Run the absolutely shortest cable you can to your inside antenna. Both antennas must be tuned to the frequency of interest. Unfortunately, since celluar phones are frequency agile or spread spectrum, you want antennas that have a somewhat wide band around the frequency band- don't forget that transmit and recieve from the tower may be on separate frequency bands.
-OR- work hard and get a window office. This is probably the most effective solution to your problem.
With all sorts of cheap electronic gadgets available, there isn't the same incentive to play around with electronics as there has been in the past. Who needs to build a shortwave radio to find people to talk to, when the Internet has made long distance chatting trivialy easy?
Work the other interests into it. If the child reads about Tesla... build a Tesla Coil. (I guess that would need some pretty good adult supervision, too).
What you can do is find things that interest the child and see how you can work electronics into it. If they are already into computers and basic programming, microcontrollers are a good start (and a personal favorite of mine) They can teach about the basics of computers without becoming overwhelming- the Microchip PIC series, especially the 16F84 is a good choice, relatively cheap, can be programmed with *really* cheap hardware, and the development tools from Microchip are free. You as the instructor must become proficient in them first, to not add to the frustration of your student. Blinking LEDs can be an introduction to the wide world of electronics- because once they know they can do it, they will be primed to learn more. There are a number of other microcontrollers that have even simpler programming interfaces than Microchip's- such as a Basic Stamp from Parallax.
To really keep their interest, you need to have payoff early- they need to see that they can do neat stuff before the theory gets pounded into them. Thankfully, with digital electronics, you don't have to worry as much about currents and Ohm's law to get results. The math will come, but it doesn't have to be the first part. They will be much more interested in learning why something works, after seeing it work, but you have to do both- a lot of the kits that you can find just show how to build it- without giving any insight into why it works. The why may be up to you. It will require work and commitment on both the teacher's part and the student's part.
I lived in Maryland when they made us start dialing area codes for the local calls in the DC suburbs- it used to be that I just had to dial a 7 digit number from the DC suburbs of Maryland (301) and get to Virginia (703) and DC (202). They started running out of prefixes, since they couldn't duplicate the prefixes within the suburban DC area. So we had to start dialing area codes to get to Virginia and DC. There was a huge uproar over that. You would have figured that life as we know it was going to cease to exist. It didn't, the phones kept ringing. Then they went to an overlay (multiple area codes covering the same area) and there was another uproar. It happened, and people got used to it. I moved to central Texas (512), and now I only have to dial 7 digits for a local call. It was a weird transition, but I survived (I can dial the area code first, but it doesn't make a difference). In the numbering plan for the area, we will be going to an overlay soon. And again, we will hear all sorts of uproar.
Big effin deal. People will complain, then they will get used to it. It is a matter of growth and progress. People should be proud of the fact that they need more phone numbers- more people in the area, a larger tax base, people are getting better connected- it really is a good thing! It just shows how wired and high tech your area is.
If you take the time to look at their website:
Cogent has many distinct market advantages to enhance your real estate investment... from
this page.
This is being marketed as something to install in the apartment building you own, not really as a personal connection to the internet.
On the other hand, considering building managment, do you really want the building super to also be your sysadmin?
Physical security is very important- you've got to make sure that the thieves don't walk off with your security system.
Preferably you should have some sort of off-site security storage of those important images. If you've already got a full time link, think about FTP-ing the images to some where else. If someone does break in, you need to keep a copy of that picture on a machine that they can't steal. Unfortunately the images you're going to get with most simple cameras are going to be pretty poor- unless the miscreant puts their face *right in front* of the camera, it will be difficult to positively identify them. Cameras all over the place will probably be more effective as a deterrent. Who says that each one has to be hooked up?
You could also tie this into a pager- but again, you need something that is protected from the thief.
Also, don't forget to increase your vigilance over the coming months, since the thieves know which home they plundered, they also know who's probably going to be getting nice new (replacement) equipment in the near future.
If you think about this device, and what its mission is, it isn't very far off from a cruise missle, except that it doesn't blow itself up when it completes its mission. It comes back to fight another day. Cruise missles suffer from the same vulnerabilites, they've got multiple navigation sources (GPS, inertial, landmarks), and sat. communications, where they can be re-targeted if needed.
The first such mission envisioned is the suppression of enemy air defenses.
I think that this means the ground based, anti-aircraft installations (guns, missles, radar) The airframe is a pretty stealthy design, which is right for going against that sort of target. That type of mission is the most dangerous for a human pilot. I'm sure Congress likes it, since if one of them goes down in combat, they don't have to tell their constituents that they are sending their children to death in some far off country.
I would think air-air combat is a much harder problem, but it would be very good to take the human out of the loop- The plane could then do continuous hi-G turns, both positive and negative, stuff that would knock out a human in seconds.
While the article doesn't come out and say it, I'm guessing there will be serious total bandwidth limitations- since there are no tracking antennas, and since this is referred to as part of a satellite TV service, it must be from (and probably to) a satellite in geosync orbit. All traffic is probably going to just one satellite. Once a lot of people sign up for this- popularity will kill it- since I'm sure that they can sign people up to long term contracts faster than they can put more transponders up.
Plus there is the fact that anything beamed to you is probably also being beamed to everyone in a multiple state area around you. I sure hope they have some *strong* encryption built in. They ought to be doing something better than DES, no?
I hate to say it, but the microsoft backed Teledesic system is a much better system (many satellites in low earth orbit- kinda like a cellular system) the satellites are closer and cover smaller areas, so the amount of bandwidth/satellite is much smaller.
Can't get to the website due to errors over there, but if this kit is based on the BA1404 chip like the Ramsey FM10 (which, for this price I think it has to be) you may have serious problems receiving what this thing puts out on many FM receivers. The BA1404 uses a tank circuit (an inductor and a capacitor) as the part that sets the frequency, and this can drift really badly. Many FM recievers today are PLL based (if it has a digital display, it probably is) and can't tune in an analog sense. If the signal drifts off of the FCC "channel" (they go in 200KHz increments, starting at 87.9 up to 107.9), many receivers won't, and if they do at all you get a really noisy signal. An FM discriminator can pull in a signal a few KHz, but they are generally designed to work within the frequency specification that FM broadcasters are mandated to follow by the FCC, which is *much* smaller than the frequency precision an L-C tank will give you.
There are FM transmitters out there that don't suffer from this problem- they use a crystal controlled PLL circuit to set the frequency, Ramsey sells one. But it is much more complex, and more expensive (I think Ramsey's is about $150)
Is Slashdot really a news source? Merriam-Webster defines news as this: "1 a : a report of recent events b : previously unknown information". I don't think so. There are pointers to news sites and discussion about them, but the news isn't reported here. The editors are not reporting things as fact. Yes, there are features, but they aren't news, usually it is just opinion or some sort of review. Otherwise what we find here are editorials, which again, according to Merriam webster: : "a newspaper or magazine article that gives the opinions of the editors or publishers; also : an expression of opinion that resembles such an article" The operative word there is opinion.
I use slashdot more as a news clipping service- where I can find out about things without having to scan all the news sites myself.
And how are the "real" news sources held accountable anyway? They can be pointed out as "wrong" by their peer journals, or they can be sued in court for libel. Anyone is free to point out something as wrong right here, and nothing prevents prevents anyone here- including the comment posters- from being sued. There is no guarantee that any media is free from bias, and it is pretty fact that the editors of slashdot have biases. Very often those biases match with the readers, so they aren't noted as biases.
The symbol is one for an angstrom -- which is 10^-10 meters. I think if that distance was significant, there wouldn't be much market for these things.
We've only got a few months left in the year 2000- I want my personal Jetpack we were all supposed to have by now!
Guys give us a break. Tell us if you are running out of topics. We'll do the homework for you. But don't please let every other posting be something of only US interest.
Unfortunately, the US Presidential election is of more than just US interest. What will be determined is who will lead the United States. How much influence the United States has is debatable, but what can't be denied is that the US has international influence. Look some of the mainstays of our vocation/avocation. Intel: based in the USA. Cisco: Based in the USA. Sun: Based in the USA What these companies do extends far beyond the borders of the US. Yes there are some other players, but if you took these away, the high tech world would look very, very, different.
You can stick your head in the sand and act like the US presidential election doesn't matter. Your choice. But the world is a lot like the internet- connected in many different places in many different ways. This election will influence your life. Maybe not as much if you're not in the US, but it will.
He asserts that there are only three (spatial)dimensions. I've been reading _The_Elegant_Universe_ by Brian Greene, which is largely a book on superstring theory, which points to 10 (or 11) dimensions, with the saptial dimensions other than x,y,z (the normal ones we use every day) being very, very small (on the order of the Planck length. While there appears to be no real proof of string theory, it has been shown to be very good at predicting things that can be observed, and provides a unifiying framework for all forces (weak, strong, EM and gravity). But I digress- he asserts that Life could not exist if it were 2 or 4. Why? What connection is there between life and dimensions. Maybe life as we know it, but all our experiences are constrained to our three dimensional (apparent) world. Yes, its true that our 3 dimensional objects don't fit quite right in a 2 or 4 dimensional world, but it doesn't mean they can't.
As to the constants- true, the universe *as we know it* wouldn't exist if they were different, but whos to say that another wouldn't? The values of these constants may not be so precarious- if you place the ball at the very top of a hill, it's in equilibrium, but not stable- some force could easily roll it one way or another, and once it does start to move, it will keep rolling until it (coupled with friction) finds a more stable point- why can't these constants vary like that?
Maybe the big bang is a cyclic process, sometimes it forms a universe that isn't stable, so it just collapses and reforms with a new set of contants. We know about this one because, simply, we're here.
So, when (and where) can I pick up my almost free night vision goggles?
They're already here (kinda). Binoculars (with large lenses) collect more light than the unaided human eye and can serve to amplify the light- you just need to find binoculars that have large lenses and low magnification. This works especially well in low light (dusk, not dark) situations.
from that list there are only 3 (Audiovox PCX1100XL, Nokia 5180, Sanyo SCP-4000) that use analog only
They only listed the analog in their chart, but at the Sanyo SCP-4000 is dual mode (AMPS Analog/PCS digital) for sure- there are two of them in my family.
oh and with the CDMA phones, it only transmits at peak power when you scream into the thing as loud as you can
Nope. The volume you speak at affects the output power not at all. Remember, these are just bits you're transmitting. If you look at it with a spectrum analyzer, the power is always just about equal, though it may go down when you are transmitting "silence" due to the style of codec that the phone employs (the codec acts as a kind of compression scheme for voice). This is more of a battery power saver thing than anything else.