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On more than one occasion I have successfully (and significantly) improved the wifi signal a desktop computer was getting simply by taking a flat sheet of aluminum foil and curving it into a semicircle around the antenna.

Currently, I'm trying to boost signal on a desktop I have placed face down so that the dual antennas from the network card are facing straight up and I have placed foil behind them as described above.

Are there any simple rules to follow when doing this to achieve the best size 'satellite dish' and optimal distance from the antenna?

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    \$\begingroup\$ We'll need more information about your setup. There's the access point, where are the walls and other objects of significant thickness, how is the AP antenna oriented... \$\endgroup\$
    – AndrejaKo
    Feb 6, 2013 at 9:33
  • \$\begingroup\$ @AndrejaKo Alrighty, I'll take some measurements tomorrow and get back to you. Thanks. \$\endgroup\$ Feb 6, 2013 at 9:49

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I appears you are making a simple reflector. In that case, the optimum shape is a parabola with the antenna at the focus and the opening pointing to the other antenna you wish to communicate with.

The wavelength of 2.4 GHz is about 5 inches, so it would be a good idea to keep the reflector at least that far away from the antenna. Even then, you will get some diffraction effects.

Keep in mind that what you are doing may be OK for one-off experimenting but is not legal. The laptop received regulatory approval (FCC if in the US) as built, not with a reflector installed. A good reflector will cause a signficantly higher field strength in a particular direction, which most likely violates the maximum allowed field strength for the band, especially if the WiFi access point is distant and the laptop cranks up the power to the limit to try to get thru.

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  • \$\begingroup\$ Depends on the specific location; FCC puts a maximum on the EIRP and transmit power, but allows you to boost EIRP at the cost of directionality. The laptop was very likely certified with an omnidirectional antenna. \$\endgroup\$
    – akohlsmith
    Feb 6, 2013 at 18:50
  • \$\begingroup\$ @Andrew: Are you sure about that? The FCC usually does not take directionality into account. Usually there is a absolute maximum field strength you are allowed, whether that is all around or in a narrow beam. Is WiFi specifically different, or are you just assuming? \$\endgroup\$ Feb 6, 2013 at 19:03
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    \$\begingroup\$ It's been a few years since I did long-range wifi deployments so I may have forgotten a couple details but yes there is a top-out of 4W EIRP no matter what, and your transmitter power can be no more than 1W (IIRC) for unlicensed ISM; you can get up to 4W by narrowing the directivity of the antenna (i.e. focusing the beam). I'll try to find the spec again. \$\endgroup\$
    – akohlsmith
    Feb 6, 2013 at 19:29

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