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Microwave T1 Service
opal_seven writes "Initially I was skeptical of the claims in the press release. But after witnessing the setup in operation, I'm still trying to pick my jaw up off the floor. Read it and (if your not living in Tucson) weep.
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I bet they aren't 100 Mw. I'm sure they're very hot, but 100,000,000 watts is a gawdawful lot of power. Even if they are 100Mw, the primary effect would be internal burns. I've (thank goodness) never been exposed to anything like that. I'm sure it hits like a physical blow, and the muscles would probably convulse in response to the sudden stimulus of, oh, most of the nerves in the body. If they moved quickly away or the radar was only on for a very short time, I'm sure there were few long term effects. I was trying to get at the inverse square law here. The power exposure decreases with the square of the distance, so if you get belted and run a few feet away, you won't get belted anymore.
;)
The other folks here were also quite right in pointing out that a microwave oven is designed to be a high Q, and at a frequency that couples well with water molecules. Your body has host of different compounds, tissues, and organs, all with various whole body resonance lengths. Not all of the power from any source will directly interact with your body.
I was just trying to point out that the setup suggested here was probably around 10 watts, and almost certainly less than 200 watts; if the power is down around that level, then you would feel hardly any effects from the radiation even a foot away from the antenna. At a foot or more, you get far less radiation from that antenna than you get from the sun.
A few more numbers for you to use as a yarstick when someone hands you a metal rod and says "Here, hold this:"
Your typical microwave oven radiates between 500 and 1500 watts (in its cavity). As I said, the sun gives you about 1000 watts (that's whole spectrum -- I'm not really sure how much of it is in the 1.5+ Gig up to infrared range; all of which may fairly be called "microwave").
I've seen a guy burn his finger in a waveguide. He wasn't killed. He didn't grow two heads. The main effect of this stuff is heat (I suppose there could be some chance ionization effects, but not much).
Anyways, I certainly don't lay claim to more than a ham's knowledge of radio. Get an EE or a physicist to come in and give the actual lecture.
My main point is that it helps to throw some "sanity boundaries" up. If the exposure numbers are orders of magnitude lower than you get standing in sunlight, then this system will almost certainly not be dropping people, birds, and fuzzy little bunnies in their tracks.
Whenever someone starts talking about hazards, I try to take my limited knowledge and see if I can come within a factor of ten of the claimed danger. If something I know to be (almost) harmless (like standing in sunlight) is at least a factor of ten more dangerous than the worst possible case for the stated "danger," then I think one can safely conclude that the threat is overstated.
I don't think I'd recommend making a habit of standing a foot in front of, say, fighter plane threat radars, just the same. I promise you they can kill you, and while I don't know how long it would take, I'd like to experiment with non-human subjects to find out...
Parting thought: Think how much power the sun must be putting out given the inverse square law and that the energy at the Earth's surface is 1,000 watts per square meter at a distance of 93,000,000 miles!
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Victor Danilchenko
I might, however, be skeptical of the "highly secure" claim unless they're layering on some sort of encryption, which is doubtful.
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My mom's going to kick you in the face!
This is it, guys. It sounds like your huge opportunity to dominate the ISP business is about to start slipping away.
;)
The RBOC's would rather enjoy their monopolies than expand into this strange "new" market. I guess they would rather sell extra phone lines at the local ISP's than do it themselves...
Geeky modern art T-shirts
Well, I'm hope you're happy. Thanks to this story, I am feeling . . . Avarice--for the supreme gadget Lust-----for new toys Envy-----for all the bastards in Tuscon Wrath----for abovementioned bastards Sloth----I'm too lazy to move. Vanity---I deserve wireless T1. Gluttony-I need more bandwith! More! Thanks to you, I'm going to hell.
What in the heck are you talking about??? I've worked wireless point to point comm gear and satellite comm gear for years. There is *NO* reason why a point to point wireless link can't get you the *exact same* latency as a wire-bound link. RF doesn't go noticeably slower through air than through that copper wire.
The only place you get really big latencies is when you take a satellite hop. *Especially* if you take a satellite hop through one or more geostationary satellites (the ones that are 36,000 km up) If you go through one of those, you get 1/4 sec delay for each satellite you go through. (Try TCP/IP from Egypt to the west coast, going through four different satellites, you get 5-10 second round trip times. Have you done this? I didn't think so. I have.) On the other hand, I've done multiple 30 mile line-of-sight connections in series (90 miles total), with 10ms latency.
In the instance of a terrestrial microwave point-to-point connection, you will get roughly equivalent latencies as with a wire-link. Then you get down to factors such as how well connected is your provider, how multihomed is their datacenter, and such.
Go read a basic science textbook before you go spouting off outrageous claims about something you know *nothing* about, and have no experience with.
If you are going to slag wireless links, do it for some other reason than the false claim that they are slow. Mention things like rain fade, or keeping antennas or dishes aligned. But don't say it's slow, cause it is simply not true.
Directionality is all a matter of antenna size divided by wavelength; beamwidth in radians is roughly equal to D/lambda (1.3 D/lambda for a circular plane radiator). With the proper antenna design you can be as directional... or not... as you want. As long as you can get enough power from the transmitter to the receiver to satisfy your signal/noise ratio requirements, you're all set.
I'd expect the towers for these babies to look like PCS towers: many tall, skinny rectangles (very narrow vertical beamwidth, much wider horizontal beamwidth) arrayed around a pole. The subscriber dishes only have to point at a server tower. If a server tower starts getting overloaded, it's not that difficult to further subdivide the horizon by using more and wider (smaller horizontal beamwidth) antennas; this lets you distinguish between subscribers separated by smaller and smaller angles. Eventually you have so many connections it pays to put in fiber and use the RF spectrum for land mobile.
Time is Nature's way of keeping everything from happening at once... the bitch.
Let's see. It's wireless, it's aimed at businesses... Yes, spread-spectrum point-to-point tech is relatively secure, but radio is radio.
Personally, I wouldn't feel comfortable using such a service without at least one level of encryption of the actual data-stream being involved. YMMV
--The more you know, the less you know.
This sounds pretty nice, and I hope it or something like it makes it out to the SF Bay area before my ludicrously expensive DSL contract is up for renewal.
I have a few obvious questions on what kind of service that $129 gets you:
$129/month seems like a good deal, but I really want to see The Fine Print first.
Schwab
Editor, A1-AAA AmeriCaptions
Okay, I realise that I'm being terribly picky but I've seen this so many times its just beginning to really wind me up.
Your != You are
The word is you're. Notice it contains an apostrophe and an e on the end. Not difficult really, but it seems to cause so many people on here a problem. Just because we are geeks/nerds doesn't mean we shouldn't be able to write correct English, does it?
That's for the delay in the air. The delay in the equipment for buffering data, creating and checking the Trellis or Viterbi error-correction codes, and whatnot are what eat the time in short-range RF communications. This can all be cut with dedicated hardware; it's not intrinsic to the medium.
Fiber is actually slower; the velocity factor of glass is something like 0.6. On the other hand, a 300 THz carrier has a lot more bandwidth potential than a 2.4 GHz one. Fiber is eventually going to displace RF for point-to-point users, but RF can help build the market for fiber. RF will then recycle the spectrum and go on to serve the mobile market.
If that's what you think, go ahead and invest your retirement portfolio accordingly; take these microwave internet stocks and sell them short. Next year, tell us how many years longer you're going to have to work before you can retire.Time is Nature's way of keeping everything from happening at once... the bitch.
I hear rumors about a startup company in Utah that'll drop ethernet into your home for about $20, lets you run servers on your system for about $40. 10 megs both ways is pretty hard to beat.
This is just like television, only you can see much further.
Damn, just thought of a few more:
Schwab
Editor, A1-AAA AmeriCaptions
Ricochet is based on cellular telephone technology. The area is geographically divided into cells and each cell has one or more omni-directional antenna towers. The Ricochet modems also have omni-directional antennas. Ricochet operates at lower frequencies where non-directional transmission is feasible, which limits its bandwidth. However, you can use Ricochet anywhere in its coverage area.
The "new" technology in question is simply point-to-point, line of sight microwave transmission. In each cell there is a tower with multiple antennas covering the various azimuthal sectors. Each client has a fixed antenna set up on their roof pointed at the tower. Similar setups have been used for communication links in the military since the 1960s. This isn't a portable, use anywhere system like Ricochet. The equipment on the client's end is just like DirectPC, the difference is that it is pointed right at your ISP's tower, which serves a lot fewer customers than a satellite so uplink & downlink traffic is feasible.
You do mean 100mw, I hope. While some very ignorant people (and that isn't a crime, folks; people just need the facts -- that's what the 'net is about -- the only cure for ignorance is confession) are shouting here about the "dangers" of microwaves (as if they were magically different from sunlight), being within a few dozen feet of a transmitter outputting 100 Megawatts would, indeed, be very deadly. Mw would be Megawatts, mw would be milliwatts.
Folks, let's put this in a little perspective. You receive about 1000 watts per square meter of RF energy from sunlight. Standing in direct sunlight complaining about the RF energy from a microwave antenna on a rooftop is like calling your neighbor during a hurricane to complain that his cat is breathing on your tree! (I wish I could take credit for that comparison, but I read that in an article about low freq RF from power-lines).
The amount of energy you receive from a point source of microwave energy is in inverse proportion to the square of the distance. I'd be very surprised if these systems are putting out more than 10 watts, and I assure you it would be illegal for them to put out more than 200 watts without special FCC dispensation. Let's be impossibly pessemistic. If, at one inch away from the antenna, you receive 100% of the radiated power, or 200 watts, then at 2 inchs you receive 1/4 of that, or 50 watts. At four inches you would receive 12.5 watts. At about a foot away we are getting into cat breath territory.
evilpenguin, aka, Michael Schwarz, aka N0ZES