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WLAN Link test aid

A device that will help you align and peak your wireless lan antenna's.

Written by: G4RFR ( FRARS ) Tuesday, 2 April 2002

Click for full size imageWhen setting up your Wireless lan point to point link, it's often a pain to have to rely on slow responding bit error rate indicators often found in software etc.

Today, the 1st of April 2002, myself - G7EYT, Carl - G6NLC, Neil - M1NCD and Steve - M1FBB completed a link test over a 2km obstructed path with good results.

Initially, the link was tested with wireless lan equipment, and no signal was received so an alternative method of antenna alignment was sought. A 2.45Ghz ISM band camera was obtained and attached to a Lucent 14Db yagi, This assembly is attached to a pole that can be extended to around 25Ft in height.

The initial test had Carl and Neil at a point we thought should be able to get a resonable link with no problems. Here, Carl and Neil had the camera and antenna along with 12V battery for power. Myself and Steve had a satellite receiver, small LCD television and an S-band downconvertor and antenna. The idea was to establish a link with video which will give an idea of the path along with associated losses etc.

This first test was a good result even though the camera only has a power output of maybe < 50mW. At the receive end, the antenna used is a box of 4 double quad antenna's giving a good 15Db of gain.

The second test was from Carl's house to Steve's house and again after elevating the TX antenna some 10Ft above roof level, a picture was obtained at Steve's house. Thanks must go to John, G0API who provided us with a large aluminium pole to get the TX up another 20ft!!.

The main advantage of using video to prove the link is that video is very simple to look at and easily determine signal quality. As an 11Mb Wireless lan signal will be around 22Mhz wide, this ties in nicely with the bandwidth used for video.

This proves that even an obstructed path of around 2Km is possible with very low powers.

The next phase of this link is to mount antenna's outside at each end, and connect WLAN equipment and establish a link.

The pictures below are screen grabs from the video we recorded of todays link tests. The white thing you can see in most of the pictures is the top of the Lucent yagi antenna. The other picture is of a lesser spotted Neil.


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