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

 


Forgot your password?
Close
typodupeerror
×
Technology

Amateur Radio Packet Over 802.11 Cards 189

Posted by timothy from the don't-call-tech-support-for-troubleshooting dept.
Skuld-Chan writes: "I stumbled across this the other day -- basically discusses modifying common 802.11 boards for amateur radio bands (or Part 97 rules). Under Part 97 there is a 100 watt limit and no gain limit (unlike the 6 db gain limit on Part 15). I thought it was interesting :)." Consult your friendly branch of the FCC :) Note that this is just one of several interesting projects from this site.
This discussion has been archived. No new comments can be posted.

Amateur Radio Packet Over 802.11 Cards More

Amateur Radio Packet Over 802.11 Cards

Comments Filter:

  • interference (Score:3, Insightful)

    by CmdrTaco (editor) ( 564483 ) on Thursday March 28, 2002 @09:29PM (#3245827)
    What kind of interference will this cause? If everyone with with 802.11 capabilities starts broadcasting, will it cause any problems? I've heard bluetooth and things like microwaves and 2.4 GHz cordless phones don't get along so well with this technology.
    • I'd hate to think of this. The author mentions reprogramming the off-the-shelf device to use another frequency range (that of Australia -- go figure). It's not the people that know what they're doing that I'm worried about, it's the radio equivalent of script kiddies... Chances are that your microwave oven will produce more interference than a 1 Watt transmitter in the city center, provided that the range is suitably offset, but I know some people that would put a transmitter capable of roasting passing pigeons behind their standard 802.11 device.

      I just loved the bit where the author mentions that you just have to use a different polarity then "everyone else". Go over the adslreports and you'll find that Linksys users are recommended to put their antennae at a 90 degree angle w.r.t. each other. Now just which polarity is not being used in your area?

      It'll only be a matter of time before people start jamming 802.11 just for the heck of it.
      • First off, they author mentioned getting the manufacture to re-program them after showing your license to them. The freqs mentioned are in the 2.4Ghz ham bands so this is legal.

        Second, when you start getting above 30-50Mhz, getting serious power out is NOT easy. If you get into the S band (2.4Ghz), anything over about 1 to 3 watts is a B*TCH to get, expensive to get and expensive to operate.

        Sure when I was in the Navy (ET), we had transmitters that would and did fry a sea gull that flew too close to us, but most people don't have that kind of money.

        BWP - AKA N5VMF
        • Doesn't everyone know how to make a klystron high power amplifier? I could slap one together out of a 6 or 7 inch picture tube and 5 rare earth magnets. Tuning it would be difficult but if you let it use it's natural frequency, there would be no need to tune it at all. 2.4 Ghz at 100w, Just what the world needs.
          • I've always wondered if it would be possible to use the tube/whatever from a microwave oven (not that I'd actually try to send a 1200W 2.4GHz transmission...) for something beyond cooking food. It could be a great way to communicate long distances. So I guess a more specific question would be, "How specifically and accurately can you control the frequency and power output of a microwave oven?"

            Hope this doesn't classify me under the "radio skript k1dd13" designation... Like I said, I wouldn't actually use it, I'm just curious.

            And does anybody really doubt whether Tesla caused the Tunguska explosion? :P

            • Re:interference (Score:3, Informative)

              by AndroidCat ( 229562 )
              Once you get up to those power levels, you could try Moon-bounce relaying. Of course, you need one heck of an antenna! (This isn't Buck Rogers, some Hams do this sort of thing.)

              I suspect the bps would be fairly low, but I haven't checked on the state of the art in a couple decades. Oh yeah, add 1.5 seconds to the packet latency! :^)

              ping moon ...

            • Re:interference (Score:4, Interesting)

              by Perdo ( 151843 ) on Thursday March 28, 2002 @11:42PM (#3246292) Homepage Journal
              A microwave oven has a "white" high power amplifier inside. It tries to transmit as close to 2.4 Ghz as possible, as this is the resonate frequency of water molecules. The actuality is they produce a more "white" RF, like a white lightbulb produces a broad spectrum of light compared to a laser. Any saw filter placed on such a transmitter, would get very hot indeed, and would waste the energy that could be used to heat the food. The filter would get hot instead of the food.

              Since the RF is white, there is no way to design a feedhorn or antenna to properly radiate the power. High VSWR would kill the transmitter in a very short period of time. Food in the microwave acts like a dummy load. It absorbs the RF, so little gets reflected back into the transmitter. VSWR as low as 15% of total power out of a klystron will make it explode in just a few seconds. The electrons "piling up" forces the klystron to act like a capacitor, and the electron gun will arc with the collector, causing the glass vacume chamber surrounded by rare earth magnets to implode with a force compounded by the high voltage being applied to it.

              Suffice to say, a klystron out of tune or improperly capacitance match with it's antenna goes like a grenade.

              Make sure you disable the power supply safety interlocks and bypass the fuses in addition to cutting a hole in the door of the microwave to achieve this effect.
      • " Go over the adslreports and you'll find that Linksys users are recommended to put their antennae at a 90 degree angle w.r.t. each other."

        A general rule-of-thumb on the amateur radio side of things is that a 90-degree polarity difference between transmitter and receiver will result in a 20dB loss in line-of-sight communication. Whether the difference is actually 20dB, I don't know, but there is a loss. Why linksys would recommend this is beyond me (maybe so they can sell better/more expensive versions to overcome the 20dB loss?).
        • Why linksys would recommend this is beyond me

          Sorry, should've mentioned more context on the adslreports site. It's a forum where users (and occasionally, a vendor employee) exchange ideas, ripe and green.

          The brilliant polarization idea came from the users, not Linksys, but I've seen it so often that the myth is all over the place.

          • Re:interference (Score:3, Informative)

            by stevew ( 4845 )

            It's not a myth!

            For line-of-site, beamed, i.e. direct communications in particular. Anyone who has done 2m Transmitter hunts can tell you it's real. For that matter, try doing 2m side-band and you'll find that the average user is horizontally polarized compared to the FM croud which use vertical. Again, an easily observed difference. You put up two antennas and flip a switch, you'll see a difference in signal level.

            Now - a few of things about doing this in the US. The first issue is content rules. No bad words, etc over the ham frequencies. So that let's you off going to that favorite porn site of yours. You can forget a usenet feed. Hams are actually limited as to what the what they can say over the radio, same is going to be true of digital communications.

            Another is no encryption. No need to worry about whether you need 40 bit or 128. Can use either in the ham bands.

            What about monitoring what comes through your digital repeater station. You DO know you're responsible for it don't you?

            It's an interesting experiment idea, and I can think of some neat OTHER applications beyond the internet. Hams are into talking. Maybe this is a relatively cheap Digitial repeater system and you move Voice data over it in a wide area network using dishes?

    • It's HAMMIES doing this. They are allowed. THey know the rules and regulations, and how to stay within them.

    • Re:interference (Score:3, Informative)

      by fatboy ( 6851 )
      What kind of interference will this cause? If everyone with with 802.11 capabilities starts broadcasting, will it cause any problems? I've heard bluetooth and things like microwaves and 2.4 GHz cordless phones don't get along so well with this technology.

      As a "Joe User" with an off the shelf, Part 15 device, you must accept any interference that comes your way. You must also not cause any interference. You are an unlicensed user of the spectrum.

      As a ham on the other hand, you can modify the part 15 Device to your allocated freqs, amplify the power output and modify the antenna system. You will also have priority over the Part 15 Devices that coexist in your spectrum.

      DE KE4PJW [qrz.com]
    • That's just too bad for Bluetooth. Amateur radio is licensed for those bands. Unlicensed users are secondary and have to accept interference. If they didn't like the deal, they didn't have to build devices that used amateur radio bands.
  • My wireless router is at about eye level, about a foot away, on a shelf here in my office. If that sucker was putting out 100 watts I probably wouldn't have it so close to my head anymore...

    • Re:100 Watt wireless router? (Score:2, Funny)

      by Anonymous Coward
      I suggest you keep it on your lap. It will keep your lap warm and cause no harmful effects. I promise!
    • Radio waves don't kill you though - they just pass through you harmlessly.
      • This is ONLY for the troll to try.

        1. Jam the interlock in a microwave.
        2. Program 5 mins on high power.
        3. Insert head into microwave.
        4. Have stoner friend hit the button.
        5. Have said friend stand back as steam pours out of your head.

        What do you think microwave ovens use to cook food? Radio Waves!

        BWP

      • Re:100 Watt wireless router? (Score:4, Informative)

        by Perdo ( 151843 ) on Thursday March 28, 2002 @10:12PM (#3246048) Homepage Journal
        RF poisoning symptom progression:

        Head ache.
        Stomach ache.
        Permanent Sterility.
        Unconsciousness.
        Death.

        In other word, if the RF makes you pass out, welcome to silicone testicles and Testosterone shots for the rest of your life.

        • Re:100 Watt wireless router? (Score:2, Funny)

          by Anonymous Coward
          Erm. It's more complex than that. RF will screw with you via tissue heating; a point source like a high-powered, directional microwave antenna is most likely to do things like boiling your eyes or brain; a radar gun on a similar frequency may send you on the road to sterility *if* you're holding it between your legs with it on all the time. Full body exposure will combine elements of heatstroke with other pecularities, as your body will be heated more 'evenly' than it would be by a source of more damaging ionizing radiation- the sun. People have raised some questions as to whether long-term, uneven tissue heating from an *astoundingly* weak source- a cellphone that likely modulates its power* a hell of a lot better than any amateur station ever could- may eventually raise the risk of cancer. Of course, I do agree it'd be better to have an exceedingly low-power bluetooth module near your brain, and the actual phone chucked in your backpack, but even if you talked on a regular cellphone for hours a day, it's unlikely you could do worse than scar a brain cell or three; enjoying alcohol or cough syrup (ahem) will cause much more shock to your poor neurons.

          I'd take a minor RF burn over a sunburn, any day. (Yes, I had to try pinching the mag-mount while my 70w 144MHz transmitter was keyed up.. You learn not to do that again very quickly; I can say my fingertip has suffered no lasting damage.)

          *It's worth noting that the CDMA phones (Sprint PCS, and all the 3G systems) modulate their power *down* to the minimum level necessary to contact the base station. This is a requirement of the specification, as handsets that fail to do this would accidentally jam adjacent channels; CDMA relies on an extremely rapid frequency-sliding system, with the intent that phones may step on eachother every 2-5 seconds or so; the overall effect averages the noise, and the likelihood of interference is taken into account in determining the necessary buffer sizes and maximum bitrates of the system.

          • Re:100 Watt wireless router? (Score:5, Informative)

            by Perdo ( 151843 ) on Friday March 29, 2002 @12:10AM (#3246385) Homepage Journal
            I was witness to a darwin award winner who unlatched a waveguide and looked into the rectangle end. He said "hey, there's hot air blowing out of here". I looked at him to see what he was talking about, then destroyed two klystrons by slapping the main power breaker. Klystrons need cooling air to prevent them from cracking and implodeing after the driving voltage is removed from them.

            This warm air is also bled into the waveguide itself to drive out any moisture that would impede your signal.

            You see, the guy looked straight into a waveguide pumping out 2000 watts at 4.7 Ghz that required 30,000 watts of 480 volt 3 phase AC to generate.

            And that dude, well, that dude was dead before he finished the word "here"

            AN/TRC-170 V2 [fas.org] Army/Airforce Mobile Troposcatter. Baddest pair of micky mouse ears you will ever see on a battle field. Two 81 db gain 10 foot dishes, 10 feet in the air, and 10 feet apart. 560 foot danger zone in front of the dishes. After a few days transmitting, the ground in front of the dishes would be littered with the corpses of birds, rodents and the scavengers that came for the easy meals.
    • It is for that reason that amateur radio is licensed. RF safety is a big part of the amateur radio license.

  • Long distances... (Score:3, Funny)

    by geogeek6_7 ( 566395 ) on Thursday March 28, 2002 @09:34PM (#3245851) Homepage
    Now instead of being like "Wow! This station is 1,200 miles away!" We can be like "Wow! The interference thats making this packetloss is coming from 1,200 miles away!"
    • That is ONE thing I would not be worried about..:) Unless you manage to get a satallite for this stuff, it is strictly line of sight.. about 15-25 miles depending on how high your antenna is. Plus you better be spending some serious money on hardline to get an antenna up very high.

      BWP - AKA N5VMF
      • Plus you better be spending some serious money on hardline to get an antenna up very high.

        Nah... Just mount the transmitter on the top of the tower. Run power and controls up and transmit away. I did that with my QRP rig.

        PS. I ain't posting my callsign on slashdot too many people know where I am as it is.
      • BWP - AKA N5VMF
        Hey Gary. How are things in Conroe Texas these days?

        (Sorry, just amazed that people will put a direct link to their home address on the web.)

  • Before everyone jumps on the bandwagon... (Score:4, Informative)

    by Jay Maynard ( 54798 ) on Thursday March 28, 2002 @09:34PM (#3245852) Homepage
    ...it's worth a reminder that amateur packet radio is subject to a number of content restrictions that make it extremely poorly suited as a transport medium for general Internet traffic. It's only useful for sending stuff from one ham to another.


    That said, I may do some hacking in this area myself...


    ...de K5ZC

    • FCC and authorities in other countries are also very restrictive about the types of modulation that can be used by amateurs.
      For example, see this link

      http://frwebgate.access.gpo.gov/cgi-bin/get-cfr. cg i?TITLE=47&PART=97&SECTION=309&TYPE=TEXT

      They seem to prohibit any encryption as well.
    • Gee, nice of you to waste your mod points trolling slashdot like that. Visible is easy to eliminate.

      You say: ...it's worth a reminder that amateur packet radio is subject to a number of content restrictions that make it extremely poorly suited as a transport medium for general Internet traffic.

      The author's page, presenting yet another sucessful end run around the last mile problem, promisses:

      If your like me and are seeking a simple way to build a high speed, affordable, RF network, where you mimic the internet and have webpages, conferencing, FTP and so on, I encourage you to look into this technology and use it. If you use this technology and would like to share your experiences, or if you have questions, you may contact me. Also feel free to link to this document and or reprint any portion of it.

      So what am I missing here? How is this limited? Whatever you are talking about is at varience with other hopeful posts here. Of course, you sig, "Disinfect the GNU General Public Virus!", kinda tells us what you are all about.

      • So what am I missing here? How is this limited?

        Amateurs may not transmit a number of things, outlined in section 97.113 [arrl.org] of the FCC rules. Messages for commercial gain, obscene or indecent messages (so much for the pr0n .GIFs), any encrypted message (except ones encrypted only for authentication purposes), or any message on a regular basis that can reasonably be sent over another radio service.


        Further, section 97.115 [arrl.org] places severe restrictions on messages that may be sent by an amateur station when they did not originate at that station.


        That's what I mean by limited.


        Of course, you sig, "Disinfect the GNU General Public Virus!", kinda tells us what you are all about.

        Oh, really? What does it say to you? Probably not what you think it says. Hint: I'm not a M$ toady.

        • Oh, I see. That 115 section is bothersom. I kind of wish someone would enforce 113 decency requirements on comercial broadcasters! Hopefully, the FCC might recognize packet protocall as an intelligent monitor which meets the need for continuous monitoring of equipment. Keeping comercial broadcasters out of amature bands is a good thing, and those bands should be expanded. I'm not going to hold my breath, so I'm afraid you are right about packet radio being limited. The FCC is way behind the times on this one.

    • There are two important restrictions that should be concidered. In North America you may not transmit in code. i.e you can't use crypto. The second restriction is a tough judgement call: you can't use the amature bands for commercial use. This may restrict you from shopping on line over an amature band WAN.

      There are some other restrictions, but these are probably the two big ones that will affect the /. crowd.

      • Actually.. shopping is a little iffy.. For example, you can't use autopatch (using your handheld radio to patch into a phone like via a repeater) to call a business client, but you can use it to order a pizza on your way home.

        • but you can use it [autopatch] to order a pizza on your way home

          That varies region to region. Ordering pizza over the autopatch would be a sure fire way to get blacklisted by the locals in my area.

        • The so called "Pizza ruling" by the FCC states that an amateur radio operator may use Amateur radio to contact a business for business purposes as long as the amateur has no finacial interest in the transaction.

          Ordering a pizza online is OK, since you aren't making money on the deal. Calling a tow truck is OK, for the same reason.

          However, *dispatching* a pizza delivery over amateur radio ict verboten.

          Also, whatever link you are transmitting on must ID itself via a recognized format at least every 10 minutes if not more frequently. In AX.25, your callsign is a part of every packet you send - I don't see how you could ID on an 802.11 system, as you must send your callsign in an accepted format - I don't think sending an ICMP with your callsign in it would be accepted.

          And yes, any SSH, SSL, or encrypted files would be right out, as would porn, or commercial traffic in which you had an interest.

          Also, the issue of "third party" communications arises. If my station is talking to another ham's station, all is well, but if I'm reading /. over this link, I am conducting "third party" conversations (unless Cmdr Taco is a ham, which as far as I can tell, he is not). Third party converstations are limited - certain countries are off limits.

          Also, going to a 100 watt transmitter is really going to increase the range over which people can intercept your conversations.

          The only (ahem) reasons to to this I can see are:
          1. "mine's bigger than yours is"
          2. To completely JAM someone you don't like (normal 802.11 operates under Part 15 rules, hams under Part 97, and (to paraphase the line from Fist Full Of Dollars) "when a radio under part 15 meets a radio under part 97, the radio under part 15 is a dead radio").

          The first reason is rather pathetic, and the second is a complete violation of the spirit of amateur radio.
          • WEP is a problem as is all encryption. As far as IDing goes, My guess is that someone could modify the cards and router to do a CW ID at 20WPM every ten minutes. If you have a lot of cards, though, that would be a major disruption to the date flow.

            The other thing to remember is that while the base may be souped up, ther remote also has to be souped up to be useful. Takes extra work to soup up a PCCard.
    • would connecting to a irc server say be any different then using a phone patch to talk to a friend?

      As long as they kept it clean I don't see what harm could be done.

  • A couple of things apply here... (Score:4, Informative)

    by bovinewasteproduct ( 514128 ) <(moc.liamg) (ta) (iikralcg)> on Thursday March 28, 2002 @09:35PM (#3245856) Homepage
    First off you must be ham radio operator. Since these all operate above 50Mhz, this means you can get by with a Tech license which is no code, just study and pass the written test. Sites to check for ham radio licensing info include E-Ham [eham.net] and the ARRL [arrl.org].

    Second, any system with more that 1 watt output must be under automatic control so that only enough power as required to compleate the communication is used. You just can't pump out 100 watts to go next door. Not that 100 watts at 2.4Ghz is easy to come by...

    The nice thing is that is looks like you don't even have to touch some of the boards to do this. Talk to the manufacture, show them your license and they'll set you up with boards in the ham bands right off the bat! Nice!

    BWP
    • Not that 100 watts at 2.4Ghz is easy to come by...

      You might be surprised... Years ago, I was browsing a surplus store in my town and was absolutely amazed by the amount of radar gear that was just sitting there. I was even more surprised that the stuff was selling.

      The guy got the equipment from both the army and the national airport. No clue which frequency the stuff works on, but it's at least in the right ballpark (and yes, buyers were informed that they should clear the area of people before hooking it up :-)
    • Second, any system with more that 1 watt output must be under automatic control so that only enough power as required to compleate the communication is used.

      Ummm Wrong. You are being way to broad and generalized. it does not have to have any automatic controls. NONE of my radios that are made by companies like ICOM and Kenwood have any kind of automatic controls. even the 1.2Ghz radios that I have wasting away and collecting dust in the basement dont have and do not require it.

      Yes getting a ham license is easy, but it is not for everyone.

      Also please keep in mind that high power operation in the microwave bands isn't for the newbie (no-code tech isa newbie).. 100 watts at 2.4Ghz can kill you quite easily.
  • Wow. I can't believe my 1200 bps KPC-3 TNC will be so obsolete in this order of magnitude.
    Signup and get your ham license!
    KO6RM
    • Want to sell? I'm looking for an decently priced one... Most are more expensive than the 11mbs wireless network cards, go figure.... They still have some uses though! http://balloons.space.edu
      • Got an 8 bit computer in the back of the closet with two serial ports? The modem part is 4 dirt-cheap chips: XR2211, 567, and 2 RS232 chips. The software is dead easy assembler code.

        Back in the old days (1980) the 8 bit machine was the computer. SWTPc 6809 Flex boxes were the favorite, but just about anything was used, including TRS-80s.

    • Oh, puhleeze... heh...

      My poor little ol' MFJ TNCs are gathering dust - I used to run a packet BBS. Ended up with one ol' boy usin' it, with a W4 call - almost never got him to get on the Internet.

      When I moved, I finally took it down, and didn't start it back up.

      Been thinking about firing one up lately to see if there's any APRS activity anymore, but just haven't gotten around to it.

      Now, if we can build out a packet network with some decent speed, that'll be a whole different kettle of fish

      73 de KE4UWL
  • ...I could spread these throughout the house, garage and yard, and give my neighbors a thrill with my oddball taste in music. It would be cool if there were "tuneable" powered speakers for the off the beaten track wavelengths. Or are there?

  • I'd recommend against it! (Score:2, Funny)

    by Anonymous Coward
    There was a local guy and his wife here who got busted and sent to prison for modifying people's radios, scanners, etc. Don't be a criminal, it's not worth it. Always obey and support the law!

    • Amateurs are encouraged to modify equipment (within the rules of course), whereas the people who were busted modified equipment that required some sort of type acceptance.

      There is a long history of amateurs modifying commercial gear for their own purposes.

    • Re:I'd recommend against it! (Score:5, Informative)

      by OverCode@work ( 196386 ) <overcode@@@gmail...com> on Thursday March 28, 2002 @11:13PM (#3246219) Homepage
      One of the privileges of an amateur radio license is modifying radio equipment with the intent of operating it on amateur frequency ranges. This is why amateur radio requires a license -- if you don't know what you're doing, you can cause serious problems. The FCC places a lot of trust in ham operators by essentially giving them a blank check for experimentation.

      So yes, hams are allowed to hack wireless cards to work on their frequencies. They're expected to know what frequencies they may use, how much power they're putting out, how to resolve any resulting interference, and so forth.

      BTW, it is not very difficult to get a ham license. Contact your local radio club, or have a look at http://www.arrl.org. Just takes a bit of reading, $10, and a 35-question multiple choice exam.

      -John, KG4RUO
      • You took the words out of my mouth, but there is one additional concern - RF exposure.

        Don't crank up on a high gain antenna pointed through your neighbor's bedroom. Be prepared to show compliance with RF exposure rules anytime you put up any antenna.

        73 de KE4UWL
      • I thought you had to know Morse code to get a ham license. That seems like a rather nontrivial thing to learn. Am I mistaken here, or what?
        • You are sort of mistaken.

          Nowadays, there are three types of ham license available: technician, general, and extra. I don't currently have any amateur (ham) license, but I am studying for the general license.

          The technician license doesn't require you to copy or send morse code. The other two require you to be able to copy Morse code at 5 words per minute. Theoretically you should be prepared to send at 5 WPM, too, but apparently they assume (reasonably) that if you can copy at 5 WPM, you can send at 5 WPM.

          Check out the Amateur radio relay league's website for more details. (arrl.org)

          MM
          --
    • Part of getting your ham license is so you're allowed to modify equipment. In fact, one of the popular mods was on the Yeasu FT-530, it was a 2m/440 handheld, if you popped off a couple resistors you got 800-900mhz.. Yes, you could listen to analog cell phones, and while that part was illegal, doing the mod itself was fine.

      • Hmmm ... the Yaesu VX-5r is able to get the cordless 900Mhz phones ... and the handsets for the 48Mhz phones (the bases are blocked on the radio for some odd reason ...)

        Also ... for that radio, you can modify the transmit frequencies via software ... of course TRANSMITTING on the "extra" freqs are illegal ... but the mod is fine ... :)

        KC0MOX ...

  • 1.5 KW (Score:2, Funny)

    by giantsfan89 ( 536448 )
    Could you imagine a 1.5 KW 11 Mbps setup? Talk about the worldwide interference.

    de KO6RM

    • Re:1.5 KW (Score:1, Offtopic)

      by Mononoke ( 88668 )
      de KO6RM
      Hey Jeremy, how are things in apartment 218 these days?

      (I know I sure as heck wouldn't put my home address in a slashdot posting.)

    • I don't know about that. I only live 65 miles from the "local" UPN station and I can barely pick it up, I think it's about 5KW.

      BTW, Your license will expire Apr 21, 2002. I hope you renewed. ;-)
      • You can go across the Atlantic on 1 watt of power under the right conditions. Power helps, but a good antenna helps MUCH more.

        Broadcast 1500 watts on a wireless card, and you'll probably fry any receiving card in the same building. :)

        -John, KG4RUO
        • Broadcasting 1500 watts from a wireless card would be pretty interesting. Not only would it melt through the case of your laptop but the laptop would start to smell funny as it melted too. However if you used a highly directional antenna, that second or two before meltdown you could sterilize a several people standing in a line. I'd suggest aiming at those people already standing in line for Star Wars:AOTC. In the words of Artie, the strongest man in the world "soon you will be as cheese, boy -- melty, melty, melty."
        • Not to mention that the P4 would almost be rivaled with the amount of heat dissapation requird for 1500 watts of transmission power. I'm surprised Intel had not thought of this before. New super hot laptops, melts in your lap, not in the case...

    • It's still line-of-sight, so you won't be visible outside the area except for the smoke signals caused by fried birds and trees and airplanes. But you're really just talking about a microwave oven that's a bit less concerned about limiting its cooking area.

  • Would https be a violation? (Score:3, Interesting)

    by iamroot ( 319400 ) on Thursday March 28, 2002 @09:50PM (#3245948)
    The FCC laws state that you may not use ciphers to obscure the meaning of your transmissions. What if someone was using https, ssh, or another encrypted protocol over this? Would that be a violation? Its not really clear what that part of the amateur radio laws mean. If that would be a violation, then I'd have to wonder about the practicality of this. Aside from an alternative to TNCs, there might be problems with actually setting up a network, aside from the fact that anyone on it would need licenses.
    • I would guess that 90% of the traffic on a ham-only 802.11 network would be illegal due to content. Even some of the replies to this thread would be illegal (re: Steven Wrights 7 words you can't say on the air). A group in Tulsa, Ok is looking at setting up a Metro Area Network using modded 802.11 equipment, but my question is: why bother? You can't run high power without being a controlling op, you can't hook it to the internet because the first lid that used SSH, HTTPS, or surfed to w w w.hotmomma.c o m would bring the FCC down on the whole network.
      Face it, ham radio is meant to be experimental and bleeding edge, and 802.11b is pretty much appliance operator level stuff.
      'Course, if AMSAT could put up a bird more than once every 15 years that worked, we could push for the next one to have an 802.11 interface on it.... THAT would be worthwhile, and give me a reason to use all the 2.4G antennas and amps I bought for AO-40...

      John Gorkos
      AB0OO
    • This is good. Amateur radio is regulated as a non-commercial space. If amateur radio operators manage to create a non-commercial, high-speed packet switching network, then maybe we can reclaim some space and create a network that's much closer to the original spirit of the Internet.

  • Licence revoked: (Score:4, Insightful)

    by Perdo ( 151843 ) on Thursday March 28, 2002 @09:55PM (#3245971) Homepage Journal
    Transmit 100 watts across a city, at 2.4 Ghz, and see how long before your amateur radio license is revoked. Part of their rules are to never use more power to conduct your transmission than is necessary. Since 100mw with a high gain antenna is enough power to transmit to the limits of practical line of sight, using more than 100mw is using more power than is necessary. Also, to transmit, you must listen to the channel you are about to transmit on to insure no one else is using that frequency at that moment. Since 2.4 Ghz devices have become so ubiquitous, it is impossible to transmit without stepping on someone, somewhere.

    This story reminds me of the one about the website that teaches people to make an x-ray machine. Nice to know, but definitely not for the irresponsible masses.
    • Actually, devices running under part 97 (ham) are allowed to cause interference to the part 15 (unlicensed) devices, and the part 15 devices have to live with the interference.
      Part 15 devices have no protection from other licenced devices (Read the fine print in the manual that came with your part 15 device).
      The using more power than necessary bit, you are correct about, although for satellite/moon bounce more than 100mw would be useful.
    • As an aside, note that devices operating in the ham portions of 2.4 GHz are allowed on a secondary basis, meaning they may not interfere, and must accept any interference.

      This was a concern the first time I built a 2.4 GHz wireless network (2mbps, using Overlan gear), so I looked it up specifically.

      73 de KE4UWL
    • Since 100mw with a high gain antenna is enough power to transmit to the limits of practical line of sight, using more than 100mw is using more power than is necessary.

      Um, what if you want Omnidirectional coverage? 100mw won't get you much if you want to have a large coverage area.

      DE KE4PJW

      • Re:Licence revoked: (Score:5, Insightful)

        by Perdo ( 151843 ) on Friday March 29, 2002 @02:35AM (#3246620) Homepage Journal
        The automatic gain control on the low noise amplifier in the receive section of the card would shut down the receive path for any card inside the structure where the 100 watt omni is located. Think of when you yell into a mike and it cuts out to protect itself. So, you could provide strong signal to everyone, unless they were too close to you.

        And as the article mentioned, this applies to Packet Radio, which by it's nature has a single source and a single destination. Omni directional antennas are used primarily for point to multipoint communication not point to point as is typically used for packet radio.

        Also, remember the inverse square law when designing your network. Putting more power into your transmitter does less to improve communications performance at a distance than a properly designed antenna. High gain omni directional antennas are more efficient at propagating your signal than increasing your power to 100w.

        For instance, a 15 dBi High Performance Omni sold here [hyperlinktech.com] for $209.95 increases the effective radiated power by a factor of 100,000. A factor of 10 for every 3 db of gain. So, your standard 100mw transmitter would transmit less power than the 100w transmitter initially, but would fall off less with distance, surpassing the performance of a 100w transmitter on a standard antenna after the first few feet.

        The other route is to use a 2.4 Ghz Klystron like this [nec.co.jp] that costs in the neighborhood of $30,000 which of course can be coupled with an high gain antenna, which will not survive long at its maximum rated load.

        This is not a competition of Penis sizes or "My athlon is faster than your Intel boxen" this is a game of finesse where the sharpest mind and the most efficient system dominates through signal quality, not signal quantity.

        You get Mary on her 2.4 phone and the Muni Hospital complaining about you ruining ther gossip chat and emergency beeper service and you won't just loose you expensive 'leet 2.4 Ghz gear, you will do prison time for willfully jamming vital communications services, tantamount to a terrorist act, post 911.

        Want to be 'leet? Implement a flat panel phased array with electronic beam steering to pinpoint your distant end receiver at gain levels limited only by the precision of the real time clock you use to gate the injection of the 0-180 and 180-360 phases of your waveform.

        That would cover as many stations as you wanted, within the limits of line of sight. You could go back to college to learn the RF theory necessary to build such a device for the price of a big dumb klystron and go on to dominate the mobile gigabit bandwidth telecommunications arena. Perhaps your choice is clear.

        'cept you have to compete with me, and I'm 11 years ahead of you :)
        • Please go troll somewhere else.

          Your posts are full of technical errors and bullshit. Do you have an amateur radio license? Have you ever operated on packet radio?

          100 mW into a 15 dBi antenna produces an ERP of 3.16 W. This is an increase of approx. 32 times the ERP of an isotropic antenna.

          • nope

            yep, nope and nope.

            my bad, you are right, 3 db is 10 times in sound not rf..?

            Just trying to scare you away from using, as a distinguished gentilman called it, "an RF-SUV" when an "RF-miata" would do the trick.

            Like that 1.2 Kw 2.4 Ghz Klystron link? Those were not even available 6 months ago. Not like they could be used for troposcatter for increased range, not at 2.4 ghz anyway. But imagine the phenominal data rate that could be achieved at any line of sight distance. I keep imagineing circular polarized 30 mile gigabit pipes. Free after rebate, since you did not have to spend the 30 million dollars for a 30 mile fiber installation.

            How does that sig go?

            "Information wants to be free but fiber wants to cost a million dollars a mile"

            Thanks for doing the math for me, I was wondering how I was going to figure out what the 15 db omni was going to be worth to me on my community wireless node.

            Did you do that on a slide rule? they are great for logrithmic functions, faster than computers if you know what your doing.

            Yep, full of bs, but certainly a fan of community wireless. Hate to see that get stomped on by an RF-SUV.

            Done a few trolls yourself eh? :

            "You just whip out your $60,000 spectrum analyzer. What's the problem?"

            "Sniffing glue will kill brain cells, but you already know that."

            "This is slashdot, don't confuse us with the facts!"

            And even quoted me:

            "Any ISP that bets their business on the use of unlicensed spectrum deserves to lose"

            Granted, at least one of the men you trolled is a wanker, but that does not make us pals, since you're a brit in america, and belong to a technology political action committee. Seems to me there is some kind of law about foreign money being donated to political parties. But then you probly made it all here to begin with.

            Mad yet? Stew a bit before posting a response. I've no more time for you and want it to be worth my while when you do respond.

  • W-ERZ (Score:5, Funny)

    by Renraku ( 518261 ) on Thursday March 28, 2002 @09:58PM (#3245980) Homepage
    Thank you for listening to W-ERZ. We're taking requests.."Hi..what would you like today?" "I'd like a copy of Windows XP." "You use that garbage? Alright, coming right up. Thanks for calling! You're listening to W-ERZ, all warez, all the time."
    • What sort of music do you guys play? I heard the Windows 95 soundtrack has a lot of "pop" to it.
      • interesting, i heard that album isn't going to be supported longer. i really hope your listeners have upgraed to the latest and greatest artistic [microsoft.com] talents being shown. the eariler albums were pretty scratchy, but the group recommends listening to the most recent tracks to get a more enjoyable eXPerience.

  • moon bounce (Score:3, Informative)

    by trex44 ( 111226 ) on Thursday March 28, 2002 @10:43PM (#3246144)
    Back in the early 80s, HAM enthusiasts used to do moon bouncing using VHF (144Mhz band) 100w radios feeding highly directional helical antennas pointed directly at the moon. The idea is to use the moon as a passive satellite to bounce the signal back to earth. Back then, 300bps packet radio communication was attainable using this technique. I wonder what kind of interference levels can be expected if some HAM operator did this on 2.4Ghz today? Would the bounced signal be strong enough to cause real interference across a large portion of the globe?

    -.. . DU1DQ

    • Re:moon bounce (Score:1, Informative)

      by rcw-home ( 122017 )
      I wonder what kind of interference levels can be expected if some HAM operator did this on 2.4Ghz today? Would the bounced signal be strong enough to cause real interference across a large portion of the globe?

      Let's do the math - a .030 watt access point will deliver about -70dBm signal to a wireless card 20 meters away using dipole antennas. The noise floor is usually about -100dBm. The moon is a return trip of approximately 400 million meters, or 20000000 times further away. Signal strength is the inverse square of the distance, or 400000000000000 times weaker. Let's assume we're using a 40db dish (one the FCC would have no trouble noticing in your backyard) and you're transmitting at the full 1500 watts output. The signal is 50000 times stronger and your dish amplifies it another 10000fold. The resulting signal is now only 800000 times (or about 59db) weaker to a non-directional antenna (or a directional antenna not pointing at the sky), resulting in a signal level of -129dBm. Which is significantly weaker than a typical noise floor of about -100dBm. As you can see, amateur radio EME (earth-moon-earth) requires a non-trivial antenna array pointed at the moon to even receive such signals.

  • As someone who has surfed the web during class with lynx, an HP48 and a couple of TNC's, this sounds like a cool prospect. Amateur packet is super-slow; the only hope for it is to move up the frequency where there's the bandwidth to support faster transmissions. But there are a couple of legal problems with Internet over packet radio. From the ARRL (http://www.arrl.org/FandES/field/regulations/news /part97/) in Part 97 of the FCC rules, Section 97.113a,

    (3) Communications in which the station licensee or control operator has a pecuniary interest, including communications on behalf of an employer.

    4) Music using a phone emission except as specifically provided elsewhere in this Section; communications intended to facilitate a criminal act; messages in codes or ciphers intended to obscure the meaning thereof, except as otherwise provided herein; obscene or indecent words or language; or false or deceptive messages, signals or identification;

    (5) Communications, on a regular basis, which could reasonably be furnished alternatively through other radio services.

    Now, IANAL, but I read that as saying: No nicknames, no ads and banners, no mp3's, and no software piracy. Not to mention that encryption is illegal over the air, so your passwords are available for the world to see.

    73's, KI0PX

    • "Now, IANAL, but I read that as saying: No nicknames, no ads and banners, no mp3's, and no software piracy. Not to mention that encryption is illegal over the air, so your passwords are available for the world to see."

      Nicknames are fine, just make sure you ID periodically. A simple ping of the nearest gateway with your callsign embedded will do.

      No ads and banners? Well no, not if it's coming from your server, but banners while browsing are no problem.

      Mp3's are just data, No problem.

      No Software Piracy, Well of course, no illegal acts.

      And encryption for the purpose of control is allowed, just don't use it for everything.

      73's, N7IPB
  • Part 97 is 100 Milliwatts

  • HAM Radio: The Ultimate Geek Hobby (Score:2, Insightful)

    by Anonymous Coward
    Amature Radio is NOT dead. It's alive and well.

    If you really wanna have some fun, check out www.irlp.net, where you can use Linux boxen to provide internet linking capabilities to remote repeaters. Very very kool stuff.

    73's.
    KD6OIZ
  • be carefull with this, or you might just turn your card into a part 15.3 device.(incidental radiator)
  • Although it is true that the 2400-2450 MHz part of the ISM band overlaps with the 13cm ham radio band, it is not really a good idea to operate high power wavelan devices in this frequency spectrum.

    The problem here is that this part of the 13cm band is used by ham radio satellites. This can seriously make problems to the hams using the satellites.

    One ham shouldn't do harm to another ham. If you are a ham radio operator interested in wireless LAN please don't forget that other hams have other interests, and there are users of the satellites.

    It would be interesting to see if there is a way to modify a wireless lan card to operate on an even lower frequency (below 2400 MHz), so it could be placed into another part of the 13 cm ham radio band.

    vy 73 DG3KJU, KG6ICX
  • You can do 1200bps/9600bps amateur packet with your Handspring Visor and a TNC using the Shine Micro SM2496 $99 TNC module [shinemicro.com]. You can see my station running at www.findham.net [findham.net]

    Brian Lane
    (Yes, I'm lead programmer for Shine Micro, but that doesn't mean that it isn't a cool project).

Slashdot Top Deals

Perfection is acheived only on the point of collapse. - C. N. Parkinson

Close