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← Revision 1 as of 2002-06-15 09:38:50
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← Revision 2 as of 2002-06-15 10:30:59 →
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| =CantennaMusings= | = CantennaMusings = |
CantennaMusings
Thinking aloud about antenna design and construction. All of this information comes from sites on the Internet and shouldn't be trusted.
A ultra cheap antenna designed based on [http://www.turnpoint.net/wireless/cantennahowto.html Nalleys Beef Stew Cans] got me to thinking about ways to do something similar. In particular that site has a calculator to help you determine the right can diameter for Wifi antennas. This design is a waveguide antenna. You can find some [http://www.saunalahti.fi/~elepal/antenna2.html waveguide antenna theory here].
Of interest is the calculator on the Nalleys cantenna page. Input your can diameter and it displays the frequency ranges captured (filtered?) and spacing for the connector feeds and such. Plugging the formulas into a spreadsheet showed that useful can diameters are 2 7/8" to 3 2/3" (or 73mm to 93mm). A table of sample sizes shows:
Diam - MM |
73 |
76 |
79 |
83 |
86 |
88 |
92 |
93 |
Fractional Inches |
2 7/8 |
3 |
3 1/8 |
3 1/4 |
3 3/8 |
3 1/2 |
3 5/8 |
3 2/3 |
Decimal Inches |
2.875 |
3 |
3.125 |
3.25 |
3.375 |
3.475 |
3.625 |
3.66 |
T11 cut off |
2406.00 |
2305.75 |
2213.52 |
2128.39 |
2049.56 |
1990.58 |
1908.21 |
1889.96 |
T01 cut off |
3142.56 |
3011.62 |
2891.15 |
2779.95 |
2676.99 |
2599.96 |
2492.37 |
2468.54 |
Guide WaveLen |
30.46 |
14.96 |
11.58 |
9.94 |
8.95 |
8.40 |
7.79 |
7.67 |
1/4 Guide |
7.62 |
3.74 |
2.89 |
2.49 |
2.24 |
2.10 |
1.95 |
1.92 |
3/4 Guide |
22.85 |
11.22 |
8.68 |
7.46 |
6.71 |
6.30 |
5.84 |
5.75 |