Instructables
Picture of WiFi cantenna without pigtail
adaptor.jpg
cans.jpg
wire.jpg
n-type-female.jpg
n-type-male-to-RPM-SMA-a.jpg
n-type-male-to-RPM-SMA-b.jpg
inside.jpg
connection.jpg
There are many websites detailing the construction of cantennas, all of them referring to a pigtail. A pigtail connects the antenna to the WiFi adaptor. However, any length of cable induces signal loss through impedance of the electromagnetic wave.

This cantenna design does away with the pigtail by using an n-type to reverse polarity male SMA adaptor. This adaptor connects your cantenna directly to a WiFi adaptor without need for a pigtail.

The microwave signal is processed in the adaptor so you can then use a long USB cable to connect from the WiFi adaptor to your computer without signal loss.

The cantenna is directional so you will need something like a tripod to direct and hold the cantenna in place. Expect about a 3dB improvement of the signal, which is roughly a doubling in power, and hopefully many more access points being revealed.

I won't go into detail about the construction of a cantenna but point you towards http://www.saunalahti.fi/elepal/antenna2.html for detailed measurements.

However, do look at the slide show to see the subtle difference that obviates the need for a pigtail.

Parts List:

High power WiFi USB adaptor with SMA connection for antenna ( I use an ALFA AWUS036H)
Can - over 76mm in diameter (Long and thin is better than short and fat)
N-type female chassis connector
N-type male to RPM SMA adaptor
Some thick unsheathed copper wire (about 1 to 1.5mm diameter mains wire is best)
Solder
Four small nuts and bolts to attach N-type female to can

Tools:

Drill and bits (cone bit to make hole for n-type chassis connector)
Soldering iron
Screwdriver
Wire cutters

You can see other self-reliant things I make and do at http://www.ecopunk.org.uk

cenaadel5 months ago

greaaaaaaaat job !!!! please can you help me to make a cantenna for cdma evedo

1.9 ghz ?????? !!!!!!!

alilike167 months ago

Great job

whoispetty4 years ago
Instead of using a second adapter, could you just purchase a N-type female to RP SMA male?

Or would that not work correctly?

I'm interested in making one of these for my belkin range extender.

Here's a link to an adapter I'm talking about.
http://cgi.ebay.com/N-female-RP-SMA-male-Jack-Straight-Connector-Adapter-/160513197349?pt=LH_DefaultDomain_0&hash=item255f550525#ht_2645wt_907
TheGoodLife (author)  whoispetty4 years ago
Yes, that is perfectly okay. In fact, I used one with the following build...

http://www.ecopunk.org.uk/2010/06/double-bi-quad-wifi-antenna.html

It works much better than a cantenna.
I assume that this setup would be for a single computer?  Also, would the "N-type male to RPM SMA adaptor" work in place of any antenna?  Would a different adapter be necessary on some devices?
TheGoodLife (author)  Wilderbeast524 years ago
I have never thought of splitting the signal from a wifi aerial. However, once one computer has connected to a network then you network other computers into the system with a hub switch.

The best wifi adaptors all seem to have screw in aerials (as per the second photo in the slideshow) so an RPM SMA adaptor is probably a must.

The N-type male screws into the N-type female, into which you solder a piece of wire that acts as the new aerial inside the can.

The link in the main description will give more detail.

If you have anything specific in mind, and the name of your adaptor, then I can help you build a solution.