How To Make a cheap Wireless LAN 6dbi Colinear Antenna
This is an short description on how to make a cheap omni antenna for 802.11 wireless LAN cards.
Most people playing with this new technology are from computer backgrounds and not radio
electronics backgrounds and thus a little confused when it comes to dealing with RF technology
especially microwave technology which has been difficult even for UHF based technicians.
This antenna is a simple co-linear antenna with a gain of about 6dbi. It is easy to construct
and provided you keep the measurements close to what is stated you will find it works fine
with very little effort.
You will need ...
1 piece of enameld copper wire about 30cm long
and some sort of coaxial base to build it on.
I have used a panel mount (male) SMA connector, but it will work just fine with any SMA, N-type,
BNC or TNC connector. A panel mount female N-type would be ideal.
Start with your piece of enameld wire. The first measurement should be 60mm. At this point you
will need to make a coil of 1 turn with a diameter of 10mm. The coil spacing should be nil, so
it basically looks like a netball hoop on the wire.
The next section should be 90mm long and another single turn placed on the wire. Finally the
remaining length should be 83mm. This is configuration is 1/4 - 3/4 - 3/4 configuration.
The top length is slightly shorter because of capacitance effect.
Once you have made the wire section, solder it to a connector and away you go. This antenna is
ground plane independant, but it will not hurt to add one and you can expect a slight improvement.
You may also choose to make the antenna look a little more professional by placing it in some
PVC or plastic tubing for protection as the first bird that comes alone will adjust your radiation
pattern for you.