parabolic dishes in the rain
Wednesday, June 22 2011
It was rainy today, so it didn't make for ideal conditions for doing further WiFi range experiments using improvised equipment, but when I have a mental itch it's hard to resist scratching it. I'd had reasonable-good luck using an eleven inch piece of flat metal bent into a parabolic reflector, but I was interested in getting even better range, and it seemed I should be able to achieve it with an old DishNet reflector. (I have two of those, or three if you count the unused one still up on the roof, and they come in at least two sizes.) The idea was to place a USB WiFi dongle's tiny internal antenna at the dish's focus point. I've worked with DishNet dishes in the past and found they're best for parabolic sound gathering. At WiFi frequencies, the dB gain is significantly less than is possible from the considerably-larger 24 dB grid dishes I also use, though it seemed they might be good enough for my limited needs today.
Normal 802.11b/g long-range 2.4 GHz, 24 dB antenna on the right, and, on the left, a small DishNet antenna (for what I believe to be a ~11 GHz signal).
Unfortunately, though, it was actually a weaker performer than my simple parabolic sheet of metal. I even bolted the dish to the rail of the solar deck and used an articulated metal gooseneck from a webcam as a precise generic positioner for the USB Dongle (so as to better find the focus point), but it was a waste of time. Mind you, I was doing this in the rain with a nearby laptop sheltered beneath the solar panel, so the experience was somewhat miserable.
After getting an old DWL-810 bridge working, I found that the 24 dB dish permanently mounted to the solar deck's antenna rotator seemed to be considerably more powerful than any of my improvised parabolic antennas. Unfortunately, though, the DWL-810 is limited in terms of what it can do; it can't, for example, run any of the aircrack-ng utilities. To do all the fun new stuff I know how to do with the 24 dB antenna, I need a USB dongle with a replaceable antenna that is compatible with aircrack-ng. (I have an Amped Wireless dongle with a replaceable antenna, but it is incompatible with aircrack-ng, at least for now.)
I also tried putting a compatible USB dongle in the 24 dB dish's focus point, but unfortunately, that point falls within a plastic shroud that was not easy to access (and I didn't want to break anything, particularly with a 20 foot drop waiting patiently beneath me).
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