SOURCEFORGE » RALF » 2014 Reception of weather images

h1.  Choice and design

Among all the antennas studied, double cross antenna has been selected to be built and used in receiving weather images, as previously mentioned, which are transmitted from POES NOAA satellite. 

The most important reasons for selection were the following characteristics:

•	Right Hand Circular Polarization (RHCP)

•	Omnidirectional radiation pattern without many side lobes 

•	Does not need a rotor

•	High efficiency in terms of low angles w.r.t. the horizontal plane

•	High gain

•	High level of robustness because this antenna works well even when the measurements of its design or frequency vary a little bit

•	 Medium level in terms of complexity of construction and price. 

Moreover, the antenna will be fixed in the roof to facilitate the line of sight with the satellite. The received signal from the satellite is about twenty times higher in the zenith than in the skyline, therefore; it is necessary to have higher levels of gain in the lower angles corresponding to the position of the satellite around the skyline.

 To accomplish this, the antenna is built according with the following schematic: