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+# Introduction
+That  Rx NOAA App, allows us to receive any of the 3 current operating NOAA weather satellites that are transmitting analogue [APT](https://en.wikipedia.org/wiki/Automatic_picture_transmission) maps in the 137 MHz band . 
+
+The [APT signal](https://www.sigidwiki.com/wiki/Automatic_Picture_Transmission_%28APT%29#Frequencies) is modulated in a AM subarrier of 2400 Hz , and then all this audio map information is broadcasted in FM in the 137 MHz band .
+
+The analogue APT weather map transmission was invented in the 60's 
+![image](https://github.com/user-attachments/assets/433e3db3-e541-42e4-bd0f-57ed64aed841)
+
+It has a resolución of  4 Kms/pixel.
+ Mínimum , 2 passes / day 
+ Continuos signal in the visual satellite range time. . (max 15 min aprox)
+
+![image](https://github.com/user-attachments/assets/97116ed9-1b42-4773-96b1-9520216b60fc)
+
+![image](https://github.com/user-attachments/assets/bc7d2365-924f-49b3-a69c-73f8ab248697)
+
+APT signal format : 120 lines / minute ,  sending two pictures at the same time (visible / infrared ) 
+
+![image](https://github.com/user-attachments/assets/c17d63f1-d898-4672-aedf-fe0bb4d1a45a)
+
+
+With our NOAA App, we need to tune any of the 3 x current  NOAA Satellite frequencies , and check at what exact time , the satellite will be visible in his orbital pass. (there are many programms and web links to check the pass to your local place ) . 
+
+Here some example of the decoded maps from that Mayhem NOAA Application , that we can record in .bmp image format  
+
+![image](https://github.com/user-attachments/assets/2eedb52f-791e-4525-9510-f7217bd51ebc)
+
+