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WiFi Antennas Reid Palmeira EE496 WiFi Specification IEEE 802.11b Uses 2.4 GHz frequency band Up to 11 Mbps Has fallback data rates to 5.5, 2 and 1 Mbps Uses only Direct Sequence Spread Spectrum Approx. 200 ft. clear line of sight range 14 total channels, 11 channels (in US) Designs

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WiFi Antennas

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Wifi antennas l.jpg

WiFi Antennas

Reid Palmeira

EE496


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WiFi Specification

  • IEEE 802.11b

    • Uses 2.4 GHz frequency band

    • Up to 11 Mbps

    • Has fallback data rates to 5.5, 2 and 1 Mbps

    • Uses only Direct Sequence Spread Spectrum

    • Approx. 200 ft. clear line of sight range

    • 14 total channels, 11 channels (in US)


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Designs

  • Pringles can

    • Effective directional antenna

  • Cantenna

    • More effective

  • Parabolic dish

    • Much more effective

    • Significantly improved SNR

    • Limits the useful range of WiFi


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Legality Disclaimer

  • Illegal by FCC regulations

    • You can only attach an FCC approval antenna to a WiFi card or base station

    • Only commercial antennas are approved

    • Enforcement provisions are minimal


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Design Considerations

  • Effectiveness

    • SNR improvement

    • Signal range improvement

  • Size

    • Portability

    • Storage

  • Cost and Build Time

    • Realistic use

    • Accessibility

  • Legality

    • If the FCC comes knocking, be French: run away!


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Pringles


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Design

  • N-Connector and pigtail from the reflector (the can) to the AP or to the WiFi card

  • Mount the injector to the side of the reflector

  • Parts must be checked to make sure matching errors don’t occur – for example standard coax cable from something like a TV will absorb the entire signal very quickly.

  • The longer the reflector (the can) the more directional and less omni-directional the antenna becomes


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Benefits of can type booster antenna

  • Improved SNR and performance

  • Increase in effective range of WiFi

  • Cost is much less than commercial antenna with similar performance

  • Build and testing times are small


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Parabolic Antenna


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Design of Parabolic

  • Shaped wire mesh bent over a parabolic frame to form a miniature grid antenna

  • Mesh material should be such that

  • Attached to the AP

  • Focal length varies proportionally with the size of the mesh dish - scalability


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Benefits of parabolic design

  • Increased security, since signal degrades behind the parabola

  • Minimal parts and build time

  • Significant reduction of interference

  • Less parts and no N-connectors, pigtails or cables means no matching problems or transmission line worries

  • No modification of any WiFi cards or modification to parts of the AP


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Testing with Network Stumbler

Green is signal

Red is noise


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