To align a simple offset antenna (such as Channel Master 1.8m with 22.6* offset angle), you need to make sure it is correctly assembled and LNB's phase center is colocated with the antenna's focal point. In addition, you should make sure LNB is pointed correctly to the proper point on the surface of the dish. It is easy to check, just point your antenna towards your due-south satellite (let s say, your central satellite has 30* elevation above the horizon), get the maximum signal and then measure the leaning of the face of the dish. If the measured angle is 30-22.6=7.4* then the antenna is assembled correctly and pointed properly.
In the case of dual-reflector antenna system (Fibo design), things are getting more difficult. Firstly, the main mirror should be properly pointed towards the satellite. Secondly, the first focal point of the subreflector should be colocated with the main mirror's focal point and should be properly oriented toward the main mirror. Thirdly, the phase center of the LNB should be colocated with the second focal point of the SUB and correctly pointed to the proper point on the surface of the SUB. Sounds like a mathematical task with too many unknowns! Well, the reality might be not so complicated, as manufacturers of the antennas already did their work.... installed LNB correctly on offset antenna. They also fixed the feedhorn and the SUB to the bottom arm of the Fibo antenna.
So, now is the question: How to transform CM 1.8m antenna to dual-reflector system?
Very simple
- you already have antenna pointed towards central satellite;
- remove original feedarms and LNB-holder;
- install new feedarms and Fibo SUB&feedhorn;
- adjust position of the SUB&feedhorn till you get maximum signal.
