I found some quite old projects on my harddisk - they still seem worth posting.
22 dBi helix antenna (85cm length)
I wanted to build a really strong and big directional antenna, helix antennas seemed easier to build than yagi’s. Difficult parts are attaching the cable connector to the copper wire and winding the wire with precision (millimeters do matter at 2.4 Ghz!). Try marking all the spots and do use tape. There’s a great tool called “Helix Calc” to get the pipe length, the diameter, the spacings and the desired output (dBi) into balance. Be aware, that the beam get’s even narrower with increasing dBi’s. Also keep in mind that helix antennas are either left or reight handed and so you need the same antenna on the other end (It’s not really the wardriving antenna, you just get problems - try biquads or omnis instead).
Here some pictures of my finished product, altough it never worked as expected (I think I never achieved the 22 dBi, I couldn’t measure the exact output because equipment for 2.4 Ghz is just too expensive - Most likely there’s a problem with the SWR). But it sure was fun constructing it..
xx dBi parabolic dish
This one’s for you if your neighbour’s access point is to far away to listen to him - give yourself a signal boost! I just attached my homebuilt 12 dBi to the arm of a regular tv satellite dish I once bought from ebay and voilà! One difficulty is centering the beam to the “burning point” of the dish - I did this with trial and error using the netstumbler signal strength indicator (I only use netstumbler for that purpose, active scanning is crap otherwise!). I too got some pics for this one (have an eye on the signal boost! - Also note that dBi is logarithmic, so a higher dBi value means an even greater signal increase):
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