From e1d375698199311ff51ddf60f7ac2c7d1acd42fb Mon Sep 17 00:00:00 2001
From: Brumi-2021 <86470699+Brumi-2021@users.noreply.github.com>
Date: Sun, 11 May 2025 23:11:27 +0200
Subject: [PATCH] Updated NOAA (markdown)

---
 NOAA.md | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/NOAA.md b/NOAA.md
index 745075c..efb085a 100644
--- a/NOAA.md
+++ b/NOAA.md
@@ -12,7 +12,7 @@ NOAA Polar Operational Environmental Satellites (POES) have an orbital period of
 
 
 
-The [APT signal](https://www.sigidwiki.com/wiki/Automatic_Picture_Transmission_%28APT%29#Frequencies) is a 256-level amplitude-modulated 2400 Hz subcarrier, which is then frequency modulated onto the 137 MHz-band RF carrier. The satellite is broadcasting it with an effective radiated power of approximately 5 watts (37 dBm) at 800 kms from the ground earth . These signals are frequency modulated (FM) and carry low-resolution weather imagery. To receive those signals , we may need omnidirectional QFH 137 Mhz antenna band or proper dipole + bandpass amplifier. 
+The [APT signal](https://www.sigidwiki.com/wiki/Automatic_Picture_Transmission_%28APT%29#Frequencies) is a 256-level amplitude-modulated 2400 Hz subcarrier, which is then frequency modulated onto the 137 MHz-band RF carrier. The satellite is broadcasting it with an effective radiated power of approximately 5 watts (37 dBm) at 800 kms from the ground earth . These signals are frequency modulated (FM) and carry low-resolution weather imagery. 
 
 The analogue APT weather map transmission was invented in the 60's 
 ![image](https://github.com/user-attachments/assets/433e3db3-e541-42e4-bd0f-57ed64aed841)
@@ -41,7 +41,9 @@ APT signal format : 120 lines / minute ,  sending two pictures at the same time
 
 # Usage
 
-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 ) . 
+Hackrf has not enough sensitivity to receive directly those NOAA APT maps with the stock rod antenna. To receive those signals , the best would be to use an  omnidirectional QFH 137 Mhz antenna band ,or a proper 137 Mhz  dipole + bandpass amplifier. 
+
+You can tune , inputting directly any of the 3 x above 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 you have,  some predict and tracking web links examples  : 
 
 To check [NOAA 15](https://www.n2yo.com/satellite/?s=25338), real time tracking position or next 10 day prediction passes to your location (based on your IP).
@@ -50,6 +52,9 @@ To check [NOAA 18](https://www.n2yo.com/satellite/?s=28654), real time tracking
 
 To check [NOAA 19](https://www.n2yo.com/satellite/?s=33591), real time tracking position or next 10 day prediction passes to your location (based on your IP).
 
+You need to adjust proper LNA , RF GAIN , VGA till getting proper signal (not weak, not saturating) , and you can adjust the audio volume till recognizing the usual beep , beep sound indicating frame A, frame B every 0.25segs. Once the RF signal adjustment is done, you can press START button for starting to capture the decoded APT weather map , and press STOP when you lose the satellite signal .
+Then the .bmp image file will be created inside SD CARD , \BMP folder. 
+
 Here some example of local test replay  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)