AO-40 mode-S experiments (in 2001)

I decided to build a helical antenna for my first tests on 13cm. The 19-turn helix with a downconverter MKU-24 by DB6NT gives a good performance in receiving the telemetrie. I was able to work on the S2-transponder at >60000km! Of course, the signals were weak, but most of them are readable.

Here you can see my main problem. I live downstairs. The antennas are all indoor, but on 2,4GHz the results must be close to zero. So I have to test it (and work with it !) in front of my window.

After 2 month with the helical, I got a (low cost) 60cm dish (f/D=0,4) from "UKW-Berichte", and the surplus gave me a cheap tripoid. So some mechanical work has to be done...

After several hours the dish was ready for the first test . The converter (in a weatherproof and isulated box) is directly connected to the feeder (2,5 turns). The antenna can be dismounted with just 4 srews !

Here the view to the "ready for test" dish. After several tests it seems that the dish is about 10db better in s/n than the 19-turn helix! The difference is nearly the same as between S2 and S1 transponder of AO-40. Obviously the systemnoice is very low compared to the helix.

73 de Michael