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2.4 GHz copper pipe Yagi
Thursday, December 23 2004
The weather today was unseasonably warm, with temperatures rising to nearly sixty degrees Fahrenheit as some sort of tropical depression swept through. It brought with it a drenching rain that persisted throughout much of the day. This afternoon I had a three hour house call in the village of Esopus, and as I was driving there across the blank spot in the topo map, the dense fog and relentless condensation on the windows made driving difficult. I can't entirely blame the condensation on the weather; for some reason I'd also brought all three dogs with me.
This evening I spent several hours building a 2.4 GHz Yagi antenna in hopes of being able to connect to a second neighbor's wireless network without having to send out ethernet pseudopodia from the household LAN. Ideally I'd like to have an arsenal of long-range cannons to point at and log onto any of a number of wireless networks, which (from the vantage point at the top of the Hurley Mountain escarpment) could measure in the dozens.
As I had for my makeshift cell phone Yagi, I used half inch copper plumbing pipe for a boom and segments of brass brazing rod for elements, of which there were twelve (not counting the driven element and the reflector). As usual, I had difficulty figuring out how best to attach the driven element to the boom without contacting metal. None of the web references are any good at providing the level of informational detail one really needs to build a Yagi. For example, what is the difference in effectiveness between a dipole driven element and a looped driven element? With a looped driven element, how far out of the plane of the elements can the loop extend without impacting performance? What are the ramifications for having a boom whose diameter is a substantial fraction of the length of the elements? What impact does the kind of metal used in the elements have?
After it was built, I tested the antenna and it seemed to be reasonably directional, though from the house it wasn't able to reach the network I had been reaching with the help of a wireless bridge on the remote end of a 200 foot length of ethernet.
The Yagi. Note the looped copper "driven element." The engineering of this antenna contains far too many guesses for my comfort. As yet it hasn't proved capable of doing what I want it to do, allowing me to log in to a remote neighbor's wireless network. This photo was taken in the first floor office, which is used mostly by Gretchen. I have the antenna pointed out the window directly at a neighbor's house.
For linking purposes this article's URL is:
http://asecular.com/blog.php?041223 feedback
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