This is how I made a usb cantenna with a coffee can. Simple and effective enough to gain 1 or 2 bars. Sorry bout the cr@ppy pics.

Step 1: Materials & Tools

Items needed:

11.5oz coffee can
Usb Wifi Adapter w/ or w/o usb cradle
Metal hanger

Tools needed:

Razor knife to cut can with. I'm not blessed with a dremel. :(
Sharpie
Ruler
Needle nose pliers and/or wire cutters
Duct tape because it has a light and a dark side

Step 2: First, Some Math.

My 11.5oz coffee can is: Laura Lynn Hazelnut creme (naturally & artificially flavored)
hell yea hazelnut bro

Inside Length 5 5/16 in.
Outside Length 5 7/16 in. (not used)
Inside Diameter 3 15/16 in.
Outside Diameter 4 in. (not used)

And we know:

1 inch = 25.4 mm
and
1/16 in = 0.0625 (decimal)

So, to use the calculator I found here: http://www.saunalahti.fi/elepal/antenna2calc.php
I needed to do some simple English -> Metric conversion.

Inside Length 5.3125 in x 25.4 = 134.9375 mm ~ 135.00 mm
Inside Diameter 3.9375 in x 25.4 = 100.0125 mm ~ 100.00 mm

The calculator gave me these figures for my project.

Target distance from bottom = 46 mm ~1.811 in ~1 13/16 in
Target depth of insertion = 31 mm ~1.220 in ~1 1/4 in
Target length of can = 138 mm my can is 135 mm. Difference negligible

Hey, I know it was for a real antenna with a Type N connector, but that just simply wasn't available to me. The principle is still the same nonetheless.

My Belkin Wireless 802.11b USB adapter/dongle: 3/8 x 1 5/8 in

Step 3: Marking and Cutting

So, I mark from the bottom of the can 1 13/16ths. This is my middle mark of the hole I need to make. Using the dimensions of my usb adapter, I just kinda eyeballed the general shape and outlined it. It doesn't have to be perfect, but just big enough so the adapter can go in. I measured from the bottom of the outside of the can since I figured I had a little fudge factor anyways.

Don't make the mistake I did and try to cut through the 'seam' of the can.

Don't ask me why I left the label on the can, either. You can see at the end that I just rolled the hole open on the right side to the necessary size. I flattened the rolled points by laying the the can on the workspace and tapping the inside of the can.

Step 4: Quick Test

Here, I just stuck the adapter in the hole and held it in place manually while I panned it around. Results with NetStumbler indicated a nominal increase, so I continued on. The second picture is when I pulled the adapter halfway out and turned it around to what I consider the backside. This part is just trial and error and also where the fudge factor comes in. Just takes fiddling with to get it just right.

Step 5: Putting It All Together

I cut the top off a metal coat hanger and straightened it. Bent 1 end in a Z shape and then added a 90 degree step perpendicular to the 'Z'. Basically you're making 2 Z's connected to each other and the latter 'Z' is there to help anchor the hanger to the can. You can make whatever mount you want. I just chose this because it was all I had.

Attach the hanger and adapter with copious amounts of duct tape. Hey, it binds the universe together you know.

Step 6: Final Product

The completed cantenna. I originally attached the hanger on the bottom hoping to make a temporary stand/tripod thingy but opted to just hang it from the curtain rod. That's why the adapter is on top instead of the bottom. The whole unit is upside down, but does not affect it in any way. It will still take some fine tuning, but I've achieved 10-15 db gain increase at least. It took my connection from Poor to Good and nearly quadrupled my download speed.

Comments please and let's all be supportive.

"now sit back and enjoy your Hazelnut Coffee while you get incredible speeds"