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Homemade antenna redux May 6, 2009

Posted by rururudy in how-to.
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coffee can antennaAm I still making homemade antennas? Can’t think of anything new?  Years ago, I gave a dorkbot talk on a can antenna.  OH MY!  I just looked at Karen’s old photo of me — I have the same facial hair after 7 years — I better shave it off before I finish this post — don’t want to be in a hairy rut!

I did an 802.11g test last week and got 10Mbps across the street with the can, but the goal is to convince KQED to replace their 1990’s  T-1 lines with a wireless link.  It’s got to look a bit better than tin cans, so I went down to Complete Fabrication and scrounged some tube out of their yard.  (MonkeyBrains.net hosts their website, and Ryan is a great guy, so he let me grab some three and a quarter inch aluminum tube.)  Jay Brommel welded the tube pieces onto some angle bar, I drilled some holes, and tonight I added the ‘element’.  Here is the final product:

Wifi CansThe measurements are thanks to the ‘How To Build A Tin Can Waveguide WiFi Antenna‘ instructions.

(The Ruler is thanks to Alameda County — you can get not only a free ruler, but your soil, paint, etc tested for FREE with a home lead-test kit — fun!  You should try it.)


wifi-pigtailThe goal is to plug these things into a wireless router (one with detachable antennas) with ‘pigtails’ that have N connector fittings on one end and wireless router fittings on the other.  N connector’s are easy to find … I picked mine up in Berkeley at Al Lashers, but the pigtails are close to impossible to find outside of the Internet (I get mine on eBay).   Wireless gear has either a RP-SMA (small) or RP-TNC (slightly larger) jack.

Do use the pigtail, I needed to pop-rivet the N connector onto a flat spot on the tube — filing down the soft aluminum gave me a stable spot.wifi-cans-003Using my trusty soldering iron (with inline kill-switch), I soldered a length of scrap copper onto the N connector.  I trimmed the wire so that it was exactly 1.21″ (30.7mm) above the white base area (if you want to know why, check out the Waveguide URL above).

wifi-cans-005I cleaned up that messy solder joint!

Tomorrow, I go over and try these antennas out, wish me luck!

Todo:
Test speed with new cans
Test the omni-directional antenna (also homemade using these instructions)
Set up multiple antennas and try 802.11n — do I need 2 cans? figure out MIMO

FYI: The remote side is set up as a  client bridge, while the connected-to-the-Internet side is set up as an Access Point.  That lets you span the LAN from one building to the next.

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Comments»

1. myReport » Monkeybrains Can Antenna - May 28, 2009

[…] latest project involves building his own wireless can antennas, as described on […]

2. anonymous - January 20, 2010

I have been tinkering around on the web about making a bi-quad antenna , is there a RF (a.k.a.) n connector to rj45 adapter. If so just post the info.. thx

3. Greg - May 12, 2011

Good idea. But I would suggest getting UAWIFI UA3 wifi adapter from http://www.uawifi.com It will work much better and more reliable on long distances. I use one in my car and one in my office. UA3 gives appx. 500 feet range in city.

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