::::: www.newrywan.org ::::: double cantenna testing

After experiementing with a single cantenna made from a 'Bounce' dog food tin with good results it was time to try the double cantenna at a distance of 3km !

I had achieved good enough results with the single cantenna but from 3km it was barelely usable pulling in around 8db.....a 1MB connection. On the node side I used a 7dbi Omni connected to 8m of RG213 to a home made pigtail connected to a Linksys WAP11 (which has been re-flashed to a Dlink 900AP+...... details here)
I used a 'Bounce' dog food can which I bought from Super Value but can apparently be bought in most supermarkets. My dog struggled with this one and lay in the same spot for a few hours after it. He didn't sound too good either.

The same can was used for the double and the top ridge was removed from the can holding the chassis mount connector and the bottom removed from the other with an electric tin opener. I then aligned the two freshly cut ends of each can together and slotted one can into the other, joining the two together. This was quite difficult to do due to the rigidity of the tin and theres not much play in it at all. This required a slight tear to be made in each can to prevent kinking when slotting together.

I've seen similar designs where conductive copper tape was used to join the cans together and maintain conductivity, but as I was eager and didn't have some readily available I decided to do without. The fitting between the cans is so tight anyway and a continuity test with a multimeter confirmed this. Next it was into the car for a 10 minute drive to my chosen test point located between Newry bypass and Bernish viewpoint. The distance to the node is around 3.2km

The laptop was setup on the passenger seat using a Cabletron Roamabout card connected to a lucent style pigtail. This was then connected to 2mtrs of RG213 which in turn was connected to the cantenna pointing out of the sunroof towards the node. The laptop in use is a Fujitsu Lifebook L440.

It took around 20 seconds to establish a connection. The Roamabout client utility was fired up and after a bit of careful aiming achieved a SNR of around 13db > 16db The signal ranged from -83db > -86db.....a stable 2MB connection. I thought the double cantenna would be more directional but a signal was still achievable when pointed 60degrees to the left or right of the node. After turning 20deg the SNR started to decrease. At this I headed up to Bernish viewpoint (3.5km) and achieved a SNR of 10 with a -88db signal. With a collector mounted on the front a few more db's could be gained from this cheap n' nasty antenna....