Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 


Forgot your password?
Close
typodupeerror
×
The Internet

Remote Feed: 72-Mile 802.11b Link 231

Posted by timothy from the that-should-reach-the-back-40 dept.
An anonymous reader writes "A 72-mile link was installed last month from San Diego to San Clemente Island, using standard 802.11b WLAN gear and high-gain, 2-foot parabolic antennas. More in this Computerworld article."
This discussion has been archived. No new comments can be posted.

Remote Feed: 72-Mile 802.11b Link More

Remote Feed: 72-Mile 802.11b Link

Comments Filter:

  • Can you say (Score:5, Funny)

    by Anonymous Coward on Wednesday November 13, 2002 @02:20PM (#4661401)
    War surfing!!!

    • Re:Can you say (Score:2, Funny)

      by SEWilco ( 27983 )
      War surfing for handhelds.
      War sailing for the big stuff (don't block the signal with your sail...).
      Make sure you take along your warchalking buoys.

  • bahh (Score:3, Funny)

    by Anonymous Coward on Wednesday November 13, 2002 @02:20PM (#4661402)
    Lovely. Now there is a path 72 miles long for people to exploit. Insecure networks, always fun...

  • 2 foot antenna? (Score:2, Funny)

    by Anonymous Coward
    Does this mean I have to wear a 2 foot antenna on my shoulder when I which to connect my laptop to the internet? This all sounds so incredible.
    • You really want a 2 foot microwave antenna broadcasting right next to your head?

      • ... Too late.
  • So now you can surf the internet from almost anywhere on their network!! *yay*

  • physics (Score:5, Interesting)

    by Anonymous Coward on Wednesday November 13, 2002 @02:22PM (#4661424)
    so how did they overcome the earth horizon limitations?

    • Re:physics (Score:3, Interesting)

      by LordHunter317 ( 90225 )
      Earth horizon limitation would be more like 300 miles. I know people who've hit that problem talking at 24GHz.

      Beat that!

      • Re:physics (Score:3, Interesting)

        by Anonymous Coward
        Earth horizon limitation would be more like 300 miles.

        I thought at sea level it was more like 20 miles.

    • Re:physics (Score:5, Funny)

      by IvyMike ( 178408 ) on Wednesday November 13, 2002 @02:27PM (#4661496)

      so how did they overcome the earth horizon limitations?

      Poles.

    • I would assume that its because of the signal bouncing off of the atmosphere. A guy by the name of Guglielo Marconi was skipping signals off the atmosphere from England to Newfoundland in 1901.
      • I think signal bounce is a function of frequency. I think 802.11b is too high to bounce.

        • Re:physics (Score:5, Informative)

          by rspress ( 623984 ) on Wednesday November 13, 2002 @03:15PM (#4661973) Homepage
          Yes at 802.11b frequencies the radio waves do not bounce, the will pretty much head out into space. At these frequencies it is pretty much line of sight, you may get a little bending in the wave but not much. You will need height at the transmit/receive site to overcome the horizion. Southern California does have one seasonal effect on radio waves however. In the summer when a high pressure area sits in the pacific ocean radio links between the west coast and hawaii are possible. This is called Troposhperic Ducting and people in So-Cal may hear radio stations both AM and FM coming in from Maui. The stronger the duct, the higher the frequency that can be passed between two points. I had a 2 meter repeater (Amatuer Radio) that was meant to be low-level, local area only. When ducting was happen my range went from about 20miles to well over 400miles. It would cover the entire Sacramento/ San Joaqiun valley stoping only when you went out of the duct. People 400 miles away sounded as if the were next door.
        • You might see some ducting if you are lucky

    • Re:physics (Score:5, Informative)

      by afidel ( 530433 ) on Wednesday November 13, 2002 @02:36PM (#4661576)
      They put it on a high tower, for 72 miles the earth bulge is ~90 feet so with fresnel zone allowance you would need an ~210 foot high tower. As to the other complaint about insecurity, at these distances the antenna's required will make an extremely straight beam, in fact the beam width is probably only in the mid single digits which is part of what makes shots this long hard, they are extremely hard to line up. Basically you would need to be on a tower inbetween the two sites and somehow intercept the information without knocking out the signal, not a trivial task. Besides they are sending seismograph data, not Top Secret documents.

      • Re:physics (Score:5, Funny)

        by jhines0042 ( 184217 ) on Wednesday November 13, 2002 @02:47PM (#4661688) Journal
        seismograph data ... and you are telling me that these dishes will _stay_ lined up?
        • seismograph data ... and you are telling me that these dishes will _stay_ lined up?
          I'll give you the benefit of the doubt, and assume you were being sarcastic, but I think that's the point of all this, is to measure seismic activity. Of course, true to /. mentality, I didn't bother reading the article to see.
      • Ok.... but the secret is .... don't get in the middle. The biggest falicy is the belief that once you put up an antenna all the signal stops at that antenna. So since it doesn't you put a larger antenna some distance behind the recieving antenna. Down side is that in a full duplex transmission link you only get 1/2 the signal. But the up side is that you are totally undetectable in that you never cut signal quality one iota.

        Second technique is to put an antenna up either sufficiantly higher or lower than the center of the beam and at this point although you get a lower signal you do still get a signal. Then it's just a matter of filters.

        Think analog not digital..... via radio even digital signal travels in waves. (3 phase partial response.)

    • Re:physics (Score:5, Informative)

      by iofire ( 521067 ) on Wednesday November 13, 2002 @04:46PM (#4662915)
      I am a student working on the HPWREN project responsible for this link, and you can find out much more information about this link and the wireless network in general at our website:
      http://hpwren.ucsd.edu [ucsd.edu]
      Also note the November 1st news item that deals specifically this with link, and includes photographs of the setup here:
      http://hpwren.ucsd.edu/news/021101.html [ucsd.edu]

    • Re:physics (Score:3, Interesting)

      by Allnighterking ( 74212 )
      OK in a sense they don't have to. First, 72 miles isn't that great a curve to deal with and second once you get into this frequecy range there are a number of Technics available for "bouncing" signal off of the Troposphere for really long shots. (100's even 1000's of miles) However for this one this technic isn't required.

      Try this.. Draw a circle on a piece of paper. Then Draw two lines out from the center of the circle at right angles extend those two lines through the circle and beyond. You will notice that sooner or later it will be possible to draw a line from the top of those two original lines that will no longer intersect the circle itself. This is the same reason you see two things One very tall MicroWave (2.4 gig is in the MicroWave band) with dishes that look like the are pointed down. (The picture you drew will show you the angles. ) Of course there are limits, like how high you can get the antenna (Mountains help) and note that the longer the shot the larger the antenna should be (concentration of more signal) but you should be able to recieve cleanly down to -90dbm0 no problem (or even lower).

      Factors that will affect the signal are. Atmospheric conditions (two antennna's swaying in the wind is the simplest example) Sun Spots buildings or trees in the line of site, and frequency. 2.4ghz can shoot further than say 7ghz can just as low frequency radio goes through the earth rather than around it. In general the rule of thumb is any time the thickness of a material exceeds the length of a single cycle the radio wave is blocked. (yes this is true of all wave transmissions and yes some materials can be made that are transparent, but I did say "in general").

      Doing a 72 mile shot over water isn't really that remarkable. At 7ghz I've seen 50+ shots over water. (Despite the statement at the end of the article shots over water are IMPROVED not inhibited by the water in the microwave range. )
      If anything the neat part or even unique part is that they did it at such a low cost.

  • The first use... (Score:5, Funny)

    by yunfat ( 200898 ) <<moc.cam> <ta> <narat>> on Wednesday November 13, 2002 @02:23PM (#4661434)
    Watson: Did you get it?

    Bell: Yes, send more porn.

  • Very Useful (Score:3)

    by jaavaaguru ( 261551 ) on Wednesday November 13, 2002 @02:23PM (#4661438) Homepage
    That would be good for my parents' house which is more than 5 miles from the nearest excahnge, but is in an ideal location for that antenna - at the top of a hill. I hope this becomes available to the masses at a reasonable price soon.

    • Re:Very Useful (Score:2, Informative)

      by mocktor ( 536122 )
      5 miles from the nearest excahnge

      you shouldn't need 2' parabolic dishes for this - it ought to be possible with a well-aimed pair of yagi [adsp.net] style antenna. (cringely article [pbs.org])
    • Doubtful, however I would love to be proven wrong.

      I think the availability will be limited to those who paid attention in the class "Fields, Matter, and Waves II" and "Microwave and Highspeed circuits" (both of which I attended, neither of which I remember a damn thing about. Maxwell who?)

      So its a good thing you are getting into antenna design as a hobby! You are getting into antenna design, aren't you?

      P.S.- good luck with those smith charts.

  • With Error Correction? (Score:5, Funny)

    by coupland ( 160334 ) <dchase@hotmailCHEETAH.com minus cat> on Wednesday November 13, 2002 @02:26PM (#4661471) Journal
    "The test was declared a resounding success when the message '@#FGGgWEe#GR... +++ATZ +++ATH0 NO CARRIER' was successfully received by the San Celemente station. Congratulations to all involved!"
  • how would you warchalk this link? I mean, besides the technical difficulties of writing on water. Do you put a really REALLY large ear on the ground near the antenna? In all seriousness, this is quite an impressive feat, especially using a highly crowded spectrum. I am curious though how it handles atmospheric interference. Over 72 miles the beam width on this thing must be miniscule and I would think any atmospheric disturbance would send the link crashing. Then again, I've never passed 802.11b traffic more than 2 or 3 miles.

  • What, no pics? (Score:5, Funny)

    by JUSTONEMORELATTE ( 584508 ) on Wednesday November 13, 2002 @02:28PM (#4661501) Homepage
    Great read, but somehow I picture something like this [wwc.edu] mounted on a 40' mast.
    --
    • I love it!~

      The feed-can really *IS* a tin can. :)

      P.S. He should drill a hole at the bottom of the can so water can get out and maybe put a plastic mesh screen over the entrance to keep leaves and bugs out. But then again, that would probably double the cost of the antennae.

  • What happens if... (Score:5, Funny)

    by Cap'n Canuck ( 622106 ) on Wednesday November 13, 2002 @02:29PM (#4661506)
    The link to San Clemente Island -- used to carry data from a seismograph, data logger and Global Positioning System receiver....

    During an earthquake, will that data registered by the seismograph still make it to the mainland?

    More importantly; if it's a REALLY big one, will the GPS record San Clemente's new position?
  • Some points:

    Problems with telecommunications in CALIFORNIA!

    Long distance on water...

    All this troubles because the 1 watt limit...

    • The 1 watt limit only applies to point to multipoint. For point to point, you can do 4 watts. BIG difference.

      Theoretically you could get 802.11b over 80 miles with ideal conditions.
  • Can you say Linksys Wan products sold by your local ISP for shareing a 128 bit isdn connection will be a huge hit for those mid sized mom and pop gas chains running linux POS systems.

  • Aluminum Vs. Silicon (Score:4, Informative)

    by n9fzx ( 128488 ) on Wednesday November 13, 2002 @02:30PM (#4661529) Homepage Journal
    More proof that a cheap $2 aluminum dish will beat a $200 silicon power amplifier any day -- and it uses the spectrum more efficiently!

    Seriously, however, broadcast medium networks like 802.11b are best used for distribution, not long distance point-to-point links (fiber is ultimately cheaper on a bit-for-bit basis), but this demonstrates that you can build a really cheap 802.11b distribtuion network to solve the Last Mile Problem. Another nail in the coffin of Ma Bell...

    • Re:Aluminum Vs. Silicon (Score:4, Informative)

      by afidel ( 530433 ) on Wednesday November 13, 2002 @02:45PM (#4661662)
      Dishes with this kind of signal amplification are not cheap, notice the $3,000 price quote. Assume $1,000 for the 2 proxim AP's this leaves over $2,000 for the dishes. Even with free AP's I decided the 25 mile link to my ISP's hq would not be worth it because of the cost of dishes. Fibre may be cheap to rent in some instances but the cost of running a 72 mile aquatic link would have been astronomical compared to the cost of this link. Also this has almost nothing to do with last mile problems specifically because this is a point to point link with a $3,000 price tag. No home user is going to shell out a $3,000 setup fee. Point to multipoint links are feasible with different kinds of antennas and they do partially solve the last mile problem, but Ma Bell has been darn good at beating back competition over the years.
      • $2000 for dishes and the towers they're mounted on.

        That's dead cheap for a large tower, especially if you have to pay a company to build it for you.
      • Time to haul out my trusty Collins Space Systems Slide Rule Calculator (circa 1974):

        A perfectly fed 2ft. diamater dish at 2.4 GHz has a gain of 24db, but even a Pringles can feed will give you a dish with 21db of gain. More importanly, the spatial extent of the signal will be minimized, allowing for cellular reuse.

        Personally, at 2.4 GHz I'd go with a loop Yagi-Uda array instead, as they're still cheap, and much more wind resistant, something you care about when pointing matters. Make enough of them and they'll be as cheap or cheaper than the Yagis used for UHF TV reception.

        Bottom line: There's nothing inherently expensive about gain antennas, and they're the cheapest way to improve the link equation.

  • And one guy on a 2.4GHz phone... (Score:3, Funny)

    by Insightfill ( 554828 ) on Wednesday November 13, 2002 @02:31PM (#4661534) Homepage
    can bring it down! Imagine, if you will, that there's a Quickie Mart in the middle of this stretch. Every time the microwave oven heats a "Pocket", the link is down.

  • How long... (Score:5, Funny)

    by Gruneun ( 261463 ) on Wednesday November 13, 2002 @02:32PM (#4661543)
    before a Corona commercial shows the guy on the beach adjusting the dish and using it as a shade umbrella?

  • 1 Watt Max? (Score:2, Informative)

    by Student_Tech ( 66719 )
    I have always been under the impression that for part 15 devices that the power is given in mv/m.
    According to http://www.radioinnovation.com/Howto/how_pass.htm the maxiumum power for a part 15 device in the 2.4ghz range is allowed an average power density of 50 mV/m at a range of 3 meters, and is a transmitter power of -3.4 dBm when used with a perfect 1/2 wave dipole. -3.4dBm is, http://www.qsl.net/vk6zse/wattsdbm.htm, between 500-800 microwatts.

    Now I realize that they are using parabolic antennas, but are they still meeting that average power density, I suspect that ERP is likely greater than 1 watt when using directional antennas.
    • The 1 watt is the max power of the Radio, not the antenna output.

      Their is some other limit for the combined 1watt radio plus antenna gain. Off hand I dont know what it is but most people in the wireless forums of www.dslreports.com know. Their have been many arguements in those forums about what is and what is Not breaking the law. Seems like its open to interpretation and the right amount of payoly to the FCC can make it favorable for one industry (wireless internet providers) or another (Satellite radio that is complaining about interference)
    • I have always been under the impression that for part 15 devices that the power is given in mv/m.

      mV/m is not power. It is electric field strength. The power is proportional to the square of the field, so (mV/m)^2 is (proportional to) power.

      Of course, since this is an EM wave, mV/m is actually an RMS value, and (mV/m)^2 is actually the average power. And of course it's not power that matters, but the power density, otherwise known as irradiance. That would be measured in mV^2/m^3. And of course there's also power spectral density, measured in watt-seconds.

      Yes, this sure does get confusing fast...

  • In further news (Score:5, Funny)

    by Brigadier ( 12956 ) on Wednesday November 13, 2002 @02:35PM (#4661559)


    Then the LA afternoon smog rolled in cause 98% packet loss. Reports of low flying sea gulls being singed as they passed through the deadly rays have also been reported.

    • Don't laugh... (Score:5, Funny)

      by thatguywhoiam ( 524290 ) on Wednesday November 13, 2002 @03:02PM (#4661835)
      Then the LA afternoon smog rolled in cause 98% packet loss. Reports of low flying sea gulls being singed as they passed through the deadly rays have also been reported.

      .. this used to happen to me.

      Not smog, specifically. A place I used to work at had a microwave connection on the roof, feeding from one of the taller skyscrapers downtown. On days when it snowed, or rained really hard, the net connection would flake out like crazy.

      'Snow Days' took on a whole new meaning.

      Tangent: a bigger problem was the various punks and squeegee kids 'playing' in the microwave field. They would jump back and forth in front of the dish for the little zap it gave you. We tried to warn them....

      ZAP 'Owww! My sperm!' ZAP 'Funny, it didn't hurt the second time... '

  • DX (Score:3, Informative)

    by Goody ( 23843 ) on Wednesday November 13, 2002 @02:37PM (#4661587) Journal
    Amateur radio operators have been doing stuff like this for years on frequencies above and below 2 Ghz. Here's a listing of distance records [arrl.org].
    • Bandwidth, most of these I think are likely either CW or voice(SSB, Narrow FM, Wide FM) a few khz at the low end(and a few hundred khz for the wide FM I think), compared to a 1Mb data signal which is (according to http://www.80211-planet.com/tutorials/print.php/97 2261) can be 30 Mhz wide ( now I suspect that is for the full 11 Mbs signal and would likely be less for 1Mbs).
      These people are also likely running more than 1 watt at 2.4 ghz.
      I think this is part of the reason that CW at a certain power will go farther than a voice signal at the same power, less bandwidth to amplify and the more finely tuned the filters can be to just receive the signal and not the noise around it.
    • All of those distances are for bounced signals, this is line of site. I work with a competitor to Proxim and asked some engineers and marketing people and this is the longest 802.11b link anyone had heard of (by quite a bit actually).
  • They must have used a huge pringles can.
  • ... Werner-Braun ... plans and develops wireless circuits that routinely span miles, including ... a 72-mile-hop installed last month from San Diego to San Clemente Island.

    And in other news, Wernher von Braun established a 200 mile hop from Baltic Coast to London [nasa.gov] using a high bandwidth high latency connection [wikipedia.org].

  • Before you ask, the horizon is still a problem. (Score:5, Informative)

    by Art Popp ( 29075 ) on Wednesday November 13, 2002 @02:40PM (#4661611)
    Which is probably why they shot over water. No trees, shorter towers. It's great to see this stuff getting tested, especially by educators who tend to publish their results. Hams have been enjoying this sort of fun for a long time now, and the basic problems are still in front of you. You have to have line of site (plus some extra height for the Fresnel effect), and you still have to buy and point dishes and since 1 watt WAPs aren't sitting on the shelf, you still have to get a pair of expensive little amplifiers. These things can at least be purchased now, and if you want to set up such a link, attend your local Amateur Radio shindig and you'll find piles of retired microwave enthusiasts, eager for the chance to lend a hand....

    • Re:Before you ask, the horizon is still a problem. (Score:4, Informative)

      by GigsVT ( 208848 ) on Wednesday November 13, 2002 @02:58PM (#4661791) Journal
      and if you want to set up such a link, attend your local Amateur Radio shindig and you'll find piles of retired microwave enthusiasts, eager for the chance to lend a hand....

      Heh, to an unlicensed operator, who is probably violating all kinds of ERP FCC limits? Not a chance.

      If anything, the only thing hooking up with hams will do is convince you to get licensed, because they likely won't talk to you much until you do, especially if they think you are going to violate FCC rules and possibly cause QRM.
      • Heh, to an unlicensed operator, who is probably violating all kinds of ERP FCC limits?

        It's really two questions.

        To an unlicensed operator?

        Yes, of course they will help unlicensed people. They were all unlicensed until they became hams, and most of them know it. I've had help on piles of radio projects from those nice folk, and returned the favors when they wanted to interface 'puters to their "rigs."

        ...who is probably violating all kinds of ERP FCC limits?

        Who said anything about violating ERP (Effective Radiated Power) limits for FCC rules. The fellow in the article specifically mentioned abiding by those rules.

        As for QRM (abbr. for interference), how much QRM is generated from a 1 watt tight-beam microwave hop.

        This issue is quite different from that of CB radio enthusiasts that transmit at 300 times (yes, times) the FCC limits for that band, stomp all over the adjacent ham band with horrible amounts of interference, and then ask the hams for help when they've blown the finals on their tube amps. Yes, that category of CBer is often treated poorly at ham gatherings. And appropriately so.

        Amateur radio isn't called called Amateur because they're beginners. It's Amateur because it's "not for profit." These fellows invest inordinate amounts of time and money participating in a community of radio enthusiasts, and if you are trying to stay within the rules and and achieve long distance radio communication there will be no end to the help/advice/parts available from them.
    • Trust me, shooting over the water isn't the easiest thing in the world. If the water is relatively calm, the signal maybe bounce and give problems.

      This situation would be OK because I doubt the ocean is going to become calm enough to cause problems but the seismic activity would throw a huge wrench in the operation. It would be wise to have a motorized mount that automatically calculates the best shot to the other tower recalibrating when signal is lost.
    • I noticed about a year ago these guys just got done testing a 100 km link in israel, but it wasn't mentioned in any computer magazine. http://www.iarc.org/~ronen/wlan.html [iarc.org] - this was in 1999.

      Become a ham - its really quite fun :). Plus this university seismic research project is really what amateur radio should be about.
  • Alien visitors picking up the signal have warchalked the area just outside of San Diego. Aerial observers have taken a photo of this this [cs.tcd.ie].

  • Isn't this in violation of FCC Part 15.247? (Score:5, Interesting)

    by GMontag ( 42283 ) <gmontag AT guymontag DOT com> on Wednesday November 13, 2002 @02:48PM (#4661696) Homepage Journal
    (b) The maximum peak output power of the transmitter shall not exceed 1 Watt. If transmitting antennas of directional gain greater than 6 dBi are used, the power shall be reduced by the amount in dB that the directional gain of the antenna exceeds 6 dBi. [bluemodal.com]

    I am just guessing at what they mean in the article [computerworld.com] by "high-gain". They say they are using a 1 watt bi-directional amp. My personal definition of high gain is a lot higher than 6dBi.

    Am I misinterpreting this?
    • probably. I am only guessing but when they say "runs with the maximum 1-watt power output allowed by the Federal Communications Commission for 2.4-GHz equipment" I assume they don't mean 1W power out of the bridge, but rather 1W effective. So assuming 24Dbi antenna's (the highest gain parabolics I have seen for 2.4Ghz) the should be ok with 100mW bridge units which is probably what they are using. I did not see them mention amp's anywhere in the article.

    • Re:Isn't this in violation of FCC Part 15.247? (Score:5, Informative)

      by DustMagnet ( 453493 ) on Wednesday November 13, 2002 @03:12PM (#4661947) Journal
      You are allowed more than 6dB gain. You just need to read a little more of the rules you quoted.

      (i) Systems operating in the 2400-2483.5 MHz band that are used exclusively for fixed, point-to-point operations may employ transmitting antennas with directional gain greater than 6 dBi provided the maximum peak output power of the intentional radiator is reduced by 1 dB for every 3 dB that the directional gain of the antenna exceeds 6 dBi.

      Fab-corp sells a 24 dBi parabolic. If my math is right, that allows you 18 dBi of gain.

      • Had seen a chart elsewhere (was really wanting to link to that) that showed the max somewhere around the 18 dBi you mention. Sorry fro tagging up the wrong language from the reg.

        Back to the real point, 1 Watt bi-directional amp + "high-gain" directional does not take much to get into violation territory. Since they left out the gain of the antenna all we can do is guess, but 2' parabolics should get you into max gain without the amp.

        Unless... [just dawning on me] the amps are only for receiving, i.e., NOT bi-directional! Now THAT would work without violation, just like some of the fancer wardriving rigs. It increases all the noise but the signal is still there to pick the digital bits out of.
        • Is there anyway to use seperate transmitting and recving antennas? You could use a big honking dish for the recving and a much smaller one for transmitting?
          • Theoretically, yes, but not sure how practical it would be, since the tranciever has only one external antenna input. I suppose you could use a splitter and diode setup of some sort (really guessing here) to have 2 antennas with one only transmitting and the other only receiving.

            Does not look like what they did, they are using 40" mesh antennas, there is a link direct to the project site in another thread.
          • Depends on the equipment. Some cards have a connector for a second "receive only" antenna, and can (in most cases) be configured to use them for the purpose you're after. These cards aren't cheap though, so expect to pay a bit more for them.

            Cards that support this sort of thing are usually noted as being capable of "Diversity", which is used mainly for noise cancellation in reflective environments, but could be used for a send/receive antenna scheme. You would want to separate your antennas by a big margin though, to avoid any sort of interference. Separation by something that reduces 2.4 Ghz signals would be best.
          • If you are restricted to a given ERP, you would not be able to increase the field strength at the receiver by using a smaller antenna and more power; all you would do is cover more area with your signal (and create more potential for interference). Plus, you have the expense of TWO antennas... it makes much more sense to use a bigger dish and reduce transmit power to remain legal, because you can squeeze a lot more out of the spectrum that way. (Sometimes the rules actually do make some sense.)
      • and since the Oronico card used in this setup is 15dBi intentional radiation per their spec sheet they have 3dBi to play with. The other thing you have to be carefull is bringing the sideband power down so that you are not tramping on adjacent spectrum (eg outside the 2.4Ghz ISM band, they really don't care how much you trounce on other 11b channels as it is an unliscensed application). I know Cisco's bridge has a 20dBi intentional output for the 350 series and they have a certified bundle using a 21dBi dish antenna for a combined power of 41dBi vs 39dBi for this setup. This is the longest shot we've heard of but in theory you could do even longer ones with our setup =)
  • 1 watt + 2ft dish at 2.4ghz would put a useable signal into a satellite in geosync orbit. 72 miles seems modest as far as range goes... the gain with a good 2ft dish at 2.4ghz is pretty extreme. If it is line-of-sight at 72 miles the signal should be way way above the noise.
  • A few people have questioned the towers necessary for this as well as have mentioned amplifiers. In San Diego, the hill at Pt. Loma has a large antenna tower on it. Perfect. San Clemente Island is no slouch on the altitude either. Another thing to take into consideration is that San Clemente Island is a military installation. The entire island is owned by the US Government. I wonder just how much they are respecting the 1 watt limit on 802.11b considering that the signal beam would be so small that interference would be nill.

  • Mmm.. (Score:2)

    by grub ( 11606 )

    I want a house along the signal path so I can enjoy roast $BIRD as they fall onto my picnic table.
  • Wow. Only 70 comments and the site's kacked and died. Is this a new record?

  • link to HPWREN web site (Score:3, Informative)

    by NspktrGdgt ( 625627 ) on Wednesday November 13, 2002 @02:59PM (#4661798) Homepage
    here's a link to more information via HPWREN's web page: hpwren San Clemente [ucsd.edu]
  • Let's say I live in a rural area, where getting broadband is not cheap.
    Also say I live in a hilly area(think Ky), but want to share my connection with my farming buddies using wireless.
    What kind of range would I expect with fairly normal equipment?
    What are the options?

  • People are going to be able to surf while surfing. Now someone just needs to invent a waterproof laptop.

    ~S

  • In other news... (Score:5, Funny)

    by r_j_prahad ( 309298 ) <r_j_prahad AT hotmail DOT com> on Wednesday November 13, 2002 @03:13PM (#4661959)
    San Diego sporting goods stores are reporting record sales of 12 ga. shotguns to San Clemente SDSC personnel who were alleged to have made cryptic statements about "frame drops", "bandwidth", and "all these f*cking seagulls".
  • in areas that experience significant rainfall and rainy season storms?

  • What about the 802.11a stuff they are doing? (Score:3, Informative)

    by LWATCDR ( 28044 ) on Wednesday November 13, 2002 @05:13PM (#4663207) Homepage Journal
    the 802.11b link was interesting but I want to know more about there 10mile+ 45mb 802.11a links.

Slashdot Top Deals

"What man has done, man can aspire to do." -- Jerry Pournelle, about space flight

Close