How-To: Build a WiFi biquad dish antenna
How-To: Build a WiFi biquad dish antenna
by Eliot Phillips, posted Nov 15th 2005 at 2:45PM
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Wireless enthusiasts have been repurposing satellite dishes for a couple years now. This summer the longest link ever was established over 125 miles using old 12 foot and 10 foot satellite dishes. A dish that big is usually overkill for most people and modern mini-dishes work just as well. The dish helps focus the radio waves onto a directional antenna feed. We're building a biquad antenna feed because it offers very good performance and is pretty forgiving when it comes to assembly errors. Follow along as we assemble the feed, attach it to a DirecTV dish and test out its performance.
Why? With just a handful of cheap parts, a salvaged DirecTV dish and a little soldering, we were able to detect access points from over 8 miles away. Using consumer WiFi gear we picked up over 18 APs in an area with only 1 house per square mile.
Building the antenna
Biquad antennas can be built from common materials, which is nice because you don't have to scrounge around for the perfectly-sized soup can. We did have to buy some specialized parts before getting started though.
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The most important part here is the small silver panel mount N-connector in the center of the picture; the entire antenna will be built on this. We purchased it from S.M. Electronics, part# 1113-000-N331-011. The "N-connector" is standard across the majority of commercial antennas and you can connect them to your wireless devices using "pigtails." The longer pigtail in the picture is a RP-TNC to N-Male pigtail that we'll use to connect our antenna to a Linksys WRT54G access point. The short pigtail is a RP-MMCX to N-Male pigtail so we can connect to our Senao 2511CD PLUS EXT2 WiFi card which is pictured. We also purchased 10 feet of WBC 400 coax cable so we wouldn't have to sit with the dish in our lap. We got our surplus DirecTV dish from Freecycle. We'll cover the reason for the mini butane torch later.
Trevor Marshall built one of the first biquad WiFi antennas found on the internet. We followed the slightly more thorough instructions found at martybugs.net. Here are the raw materials we started with:
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The wire is standard solid-core 3-conductor wire used for most house wiring. We didn't have any copper printed circuit board material laying around so we used this thin sheet of copper and supported it using the 1/4-inch thick black plastic pictured.
