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Wireless Networking Hardware

Portable Wi-Fi Antenna for Centrino Laptops? 47

Posted by Cliff from the better-range-from-the-hot-spot dept.
Quinthar asks: "For years I've been reading of amazing extensions to wifi-range, but they always seem to include external hardware rather than what's built into regular laptops. As wifi makes it almost everywhere, is there anything I can use to eek out extra coverage in the coffeeshops? I've read of USB antennae -- are these snakeoil? If not USB, how else can I plug a real antenna into a simple Centrino chipset without the hassle of an external card? My dream would be a tiny parabolic dish with a tripod that folds up neatly. Does such a thing exist? Can I hold a Pringles can up to the right spot and expect results? Basically, what are my options, and which do you recommend?"
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Portable Wi-Fi Antenna for Centrino Laptops? More

Portable Wi-Fi Antenna for Centrino Laptops?

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  • Pringles can? (Score:3, Informative)

    by diamondmagic ( 877411 ) on Thursday October 06, 2005 @06:53PM (#13735221) Homepage
    Can I hold a Pringles can up to the right spot and expect results? Basically, what are my options, and which do you recommend?

    Yes, actually. I built one, and it works quite well. I have only bothered getting signals from a mile or so, but it should work up to two or even three.

    • The only problem with the Pringles can antenna is that USA law enforcement agencies in at least 2 jurisdictions (Tampa, FL and Los Angeles, CA) consider it to be illegal (not just a violation of FCC regulations).

      I will leave it to the reader to search through Slashdot from about April, 2005 onward for the relevant articles. But you have been warned!

       
      • Nonsense! Antennas, as long as they don't send signals, are perfectly okay with the FCC (70% sure). The only power the FCC has is controlling what goes over the air. And just because enforcment thinks it is illegal does NOT mean the courts will agree. (There was no source cited in those articles, so it is impossible to tell if they are even true)
    • Namely, he still has to pull the antenna wire out of his laptop somehow, and insert it into the can.

      I don't understand how the OP thinks he's going to pull this off without some serious hardware hacking.

  • Tiny dish won't work (Score:5, Informative)

    by inio ( 26835 ) on Thursday October 06, 2005 @06:59PM (#13735265) Homepage
    reflectors don't work unless their diameter is at least on the order of the wavelength you're trying to reflect. for 802.11b/g that's about 12cm - way bigger than most people would like to carry around.

    A better alternative is the modern waveguide cantenna design [turnpoint.net] - far more compact than the original Yagi pringles can designs.
    • Another vote for the waveguide cantenna, here. I've been building and using em' for almost a year now, and they are great little devices. No idea about using them on a built in device, but that is actually a pretty bad idea; Most connectors on cards already are pretty breakable, and reattaching/unattaching an antenna will break a wireless card after a while of use. You'd have to get a separate pigtail for a nicer connection, which means dangly thingies. I'd just suggest getting a nice wireless card (suc

  • dish antenna (Score:2, Interesting)

    by LinuxGeekMobile ( 700015 )
    Here's a small dish antenna [slashdot.org] that works wonders, and you can make it yourself. You won't be able to replace the internal antenna in your notebook though. Usb antenna? Pure B.S.
  • Otherwise, how would you connect the antenna to the radio. Plus, no one ever mentions that both sides have to be able to hear each other. No good if your notebook just hears the base but not the other way around.
    • "Plus, no one ever mentions that both sides have to be able to hear each other."

      Nobody ever mentions that antenna performance is identical when transmitting and receiving - if you have 6 decibels of gain in a 60 degree frontal arc on transmission, you'll have the same 6 dB of gain when receiving.
      • But signal loss in the direction of propagation isn't is it? Also are the strengths of the two transmitters the same? I would think the laptop might use a less powerful transmitter. Not sure what other factors there might be. I'm not sure of all the issues involved, nor do I fully understand the concepts brought up here.
        • The poster above you is correct. Transmitter strengths, transmit or receive, etc don't matter one bit. 6dB of gain from an increased antenna is 6dB of gain period. It helps both transmit and receive.
    • Antennas work both ways. Gain is gain.

  • TANSTAAFL (Score:4, Informative)

    by dozer ( 30790 ) on Thursday October 06, 2005 @07:30PM (#13735484)
    Antennas generally achieve more gain by giving up coverage. Most stock 802.11 antennas are designed to radiate more or less spherically. Otherwise, you'd have to keep your laptop in a specific orientation to get a signal. Imagine the tech support... "Turn your laptop 20 degrees to the right. Anything now? Hmm. Try propping a book under the left side."

    Cantennas get great range because they are highly directional. If I twist my Pringles can more than about ten degrees, the signal drops off to nil. And since 802.11 is a two-way protocol, there needs to be an eqivalent antenna on the far end. Your Yagi won't do you no good if the Omni at the far end can't even reach halfway back to you.

    If all you want to do is listen, or send a signal from your house to your barn, cantennas are a good choice. But for a coffee shop?? Probably not. Just buy a laptop with a large antenna. Newer Thinkpads and Powerbooks generally have large built-in antennas.

    Despite all this... Does anybody know of a reasonably priced USB wifi device that will accept a pigtail and a homemade antenna? I'd like to attach a large omni to my PCI-less and PCMCIA-less in-car computer.

    • Re:TANSTAAFL (Score:3, Informative)

      by inio ( 26835 )
      And since 802.11 is a two-way protocol, there needs to be an eqivalent antenna on the far end. Your Yagi won't do you no good if the Omni at the far end can't even reach halfway back to you.


      Directional antenna radiate directionally, providing the needed gain for the return trip (and this is where you get into trouble with teh FCC).
      • there needs to be an eqivalent antenna on the far end.
        This is true as stated, however, a directional receiver ignores "noise" from other directions giving better reception of intended signals. An example of this is the parabolic microphones used on the sidelines in football stadiums. The player on the field is not amplified, but the fan noise is in effect ignored by the directional mic.
    • Sorry but that's rubbish. The only thing that would make a difference is the transmitting power: the base station would have to pump out a signal several times higher than the laptop for your scenario to be true. It has nothing to do with the antenna. If a signal can go one way between two antennas, it can go the other way just as well.
    • "And since 802.11 is a two-way protocol, there needs to be an equivalent antenna on the far end. Your Yagi won't do you no good if the Omni at the far end can't even reach halfway back to you."
      A Yagi and or canetnna are highly direction both transmitting and receiving. It will extend the range in both directions.

      Now if you could get separate transmit and receive antennas for wifi you could do some very long range legally. You could use a huge dish for the receivers at both ends and a moderate sized transmit
      • No problem, just use a Linksys with firmware that allows you to chose which antenna does what. Attach external antennas as appropriate ... problem solved. (Unless I am missing some important point.)
  • I think the "USB antennas" you're talking about are really USB wireless adapters mounted at the focal point of a parabolic reflector.

    "I'm feeling lucky" for "USB parabolic antenna" gave me this. [orcon.net.nz]
    • My room mate has an older USB WiFi card. They look like thumb drives but they are for Wi-Fi. He hookes it up to his desktop with an extention cord and hangs it near the window to try and pick up wi-fi if ever needed.

      I personaly use a Linksys Wireless-G card for my laptop. It works fine for me when I'm in wi-fi rang but I have problems picking it up in funny places or when I have a week signal.

  • Why not use an external card? (Score:4, Insightful)

    by munpfazy ( 694689 ) * on Thursday October 06, 2005 @08:26PM (#13735804)
    If you're going to be carrying around an antenna anyway, is there a compelling reason not to get a cheap wireless pcmcia card and use that instead of the internal wireless hardware?

    At the very least, that might be a nice way to start. If you're going to modify hardware, better to start with a $15 network card rather than your laptop. Then, if you discover that the external antenna doesn't help you much (because it's a pain to carry around, or because the places you hang out are still too far away from access points), you won't have to worry about returning the laptop to its internal antenna. And, if by some chance you screw up and break something, you'll be stuck with a broken network card rather than a wrecked laptop.

    As far as finding some way to improve your reception without modifying the hardware, you're probably out of luck. Outside of building some sort of active repeater (which would be expensive, potentially illegal, and a much bigger pain to carry around than any alternative), it's hard to think of a way improve the antenna in the laptop itself.

    If you want to get silly, you could carry around a large (meter size) parabolic dish and hold your laptop at the focus of it. Not very practical, but it could be fun, and is sure to lead to interesting conversations. If you can find an appropriately shaped umbrella and a few rolls of metal tape, you might be able to make a more portable version. It's possible you could even build some sort of passive reflector out of wire, if you know how the internal antenna is oriented or you're willing to jump into a lot of trial and error.

    • a lot of PCMCIA wifi adaptors will have a small round plastic plug hiding a standard-ish socket for plugging in an external antennae. this is particularly common on the older buffalo cards - you can get nice, neat external antennae for them that are small enough to fit in your laptop bag and roughly double the range.
      this is going to be way neater than cracking open your laptop and soldering something onto the antennae built into the lid of your laptop.
      see http://l8shop.net/Products/Buffalo_AirStation_2_4 [l8shop.net]
    • As far as finding some way to improve your reception without modifying the hardware, you're probably out of luck. Outside of building some sort of active repeater (which would be expensive, potentially illegal, and a much bigger pain to carry around than any alternative), it's hard to think of a way improve the antenna in the laptop itself.

      That's not true. Linksys [linksys.com] makes the WRE54G [linksys.com] range expander. Simple little device that works pretty well and doesn't cost too much. Just drop it near a power outlet and y

  • Obvious solution (Score:3, Funny)

    by MarkGriz ( 520778 ) on Thursday October 06, 2005 @09:07PM (#13736008)
    Use one of those cellphone antenna boosters, which of course you adhere to your laptop battery.

    Should provide at least the same amount of antenna boost as it does for cellphones.
    • While I was stocking up on green markers for my CD's at my local Hi-Fi shop, they also sold me this cellphone antenna booster, its great! Now I can use the phone in the cellar and I get a much clearer sound and a way better dynamic range. I want back and bought some for my friends phones, so now all my calls are in high quality. Now I just need smaller batteries for my electrostatic head set.
  • I'm faced with the same problem and found a few ways around it.
    I have a public network 3.3km away on a hill with a 500mw amp, I can sometimes see it but too week to connect. so I did some shopping.
    In total I got 2 usb wlan adaptors 3 pcmcia cards and 1 ap,
    I found that some of the old devices out performed the new ones.
    an asus wl-167g(usb g) can't see a network 3houses down, where a netgear ma111(usb b) can see half the street.
    Then I made a usb pringles antenna by inserting the ma111 usb adaptor 1/4 waveleng
  • There is no "USB Wifi antenna" on the market, but just USB wifi adapters.
    By the way, laptops (whether Centrino or not) use a quite big antenna hidden into the diplay/cover case. And this is bigger than any other "normal" external wifi antenna.
    The only good thing to be done is to ask manufacturers to add an external antenna plug, as they used to do for cell phones.
  • Check this site: http://www.hyperlinktech.com/web/1.13_custom_cabl e s.php [hyperlinktech.com]

    You can get a short adapter cable with a connector that fits your internal card (probably U.FL) and runs to a N or RP bulkhead you can install somewhere in your laptop if you can find the space. I think the Kensington lock slot should have enough empty space behind it, you should be able to drill a hole. Now you have a connector for you laptop antenna, at this point check the same site I linked above; they have portable external anten
  • You can't attach an external antenna to your centrino laptop for the same reason laptop manufacturers hardcode the PCI ID of their mini-PCI wifi cards in the BIOS: FCC Certification.
    Any WiFi hardware must be FCC certified, and certification is always performed on the radio (WiFi card) and the antenna as a whole. An (external) antenna that is not explicitly FCC certified for a particular card is verboten.

    Antennae in laptops (just open the LCD bezel to see for yourself) are relatively big -- most of the tim

  • It amuses me to see Centrino adverts saying "Internet Anywhere" or some such. Point of fact, it's not. Between where i'm sitting and my house 3km away, there are 3 hotspots, yes i've counted. It's just not everywhere at all, and if you do find it, only 1 in 20, or so, of them are actually open (whether intentionally or not). Services like Netvigator (who now have a new name, I believe) DO provide internet anywhere. Pity it's not 802.11g, eh?

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