lxe/goes16-rtlsdr.md

## goes16-rtlsdr.md

      
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              goes16-rtlsdr.md
            
          
    Receive GOES-16 and GOES-17 Images with a Raspberry Pi and RTL-SDR dongle

Also see the original Pieter Noordhuis's guide
Hardware

You need:

Raspberry Pi Model B (or B+) with a MicroSD Card $35-40
An RTL-SDR dongle:

RTL-SDR.COM V3 ~$25 or
NooElec NESDR SmarTee ~$25 or
NooElec NESDR SmarTee XTR ~$40


LNA and SAW filter for around 1.69GHz

NooElec SAWBird+ GOES ~$35


A 1.6 - 1.9 GHz parabolic grid antenna

ZDAGP1900-20-15----1850-1990MHz 20dBi ~$100 or
More dBi Options
Or use a Modified 2.4 GHz WiFi grid antenna ~$60


Adapter (depending on the antenna terminal):

N-Male to SMA Male $5-10


Cable(s)

SMA Male to Male $5-10


Total: ~$185
Assembly:
[Antenna] --- [Adapter] --- [(input) SAWBird+ (output)] --- RTL-SDR (with Bias Tee)] --- [Raspberry Pi]


Software

Prep your Raspberry Pi and install necessary drivers and software.
0. Get your Raspberry Pi ready


Download Raspbian Lite Image and Etcher
Use Etcher to write the image to the SD card.
Mount the SD card as a volume on your machine.
Follow this procedure to configure WiFi and SSH.
Plug the card into your Raspberry Pi and turn it on.
Find the IP address of the Raspberry Pi using your gateway/router administrative interface.

Now you can SSH into your Raspberry PI as pi with a default password raspberry.
1. Get everything up to date

From now on all commands should be run on the Raspberry Pi.
sudo apt update
sudo apt dist-upgrade

# reboot the device
sudo reboot
2. Install dependencies

# get the packages necessary to build and run goestools
sudo apt install git build-essential cmake libusb-1.0 libopencv-dev libproj-dev
3. Install librtlsdr

Grab the latest librtlsdr source, compile it, and install the shared libraries/includes.
# download, compile, and install librtlsdr
git clone https://github.com/steve-m/librtlsdr.git
cd librtlsdr
mkdir build
cd build
cmake -DCMAKE_INSTALL_PREFIX:PATH=/usr -DINSTALL_UDEV_RULES=ON ..
sudo make -j2 install

# load udev rules and blacklist the DVB driver shipped with the OS
sudo cp ../rtl-sdr.rules /etc/udev/rules.d/
sudo ldconfig
echo 'blacklist dvb_usb_rtl28xxu' | sudo tee --append /etc/modprobe.d/blacklist-dvb_usb_rtl28xxu.conf

# reboot the device
sudo reboot
4. Test your the RTL-SDR dongle

rtl_test 
You should see something like this:
Found 1 device(s):
  0:  Realtek, RTL2838UHIDIR, SN: 00000001
...

If it hangs, just press crtl-c to exit. It doesn't have to finish.
If there are errors, or if the device is not recognized:

Reinstall the driver from Step 3
Ensure the dongle is secured in the USB port
Remove all USB hubs and plug in into the Pi directly
Make sure you power your Raspberry Pi with at least a 2.5A power supply
Check the device using lsusb command. You should see ID 0bda:2838 Realtek Semiconductor Corp. RTL2838 or something of the like listed there. If not, try the previous steps.
Run dmesg and check for errors such as error -71 related to the USB device. This may mean that your RTL-SDR receiver might be broken. This happened to me, so I ordered another one, which ran fine.

5. Install goestools

git clone https://github.com/pietern/goestools.git
cd goestools
git submodule init
git submodule update --recursive
mkdir build
cd build
cmake -DCMAKE_INSTALL_PREFIX:PATH=/usr ..

# this will take a while on a raspberry pi
sudo make -j2 install 
6. Create goesrecv.conf config

cat <<EOF > ~/goesrecv.conf
[demodulator]
mode = "hrit"
source = "rtlsdr"

[rtlsdr]
frequency = 1694100000
sample_rate = 2400000
gain = 5
bias_tee = false

[costas]
max_deviation = 200e3

[decoder.packet_publisher]
bind = "tcp://0.0.0.0:5004"
send_buffer = 1048576

[monitor]
statsd_address = "udp4://localhost:8125"
EOF
If you're using a NooElec SmarTee dongle with an always-on bias tee, or if you're powering your SAWBird through the micro USB port, set bias_tee = false under [rtlsdr].
If you're using RTL-SDR.com dongle, set bias_tee = true to power the SAWBird board.
7. Roughly point your antenna at the satellite

Find where the GOES-16 or GOES-17 satellites are in the sky at your location using agsattrack.com.
Note the azimuth and elevation.
Use an actual real compass to point your dish at the azimuth. I've been using the iPhone phone compass, which has a 20-30 degree error, rendering it practically useless.
You can also use https://www.dishpointer.com/ which will draw a line on the aerial map where to point your dish -- I found that to be more helpful than the compass.
Adjust your dish angle according to the elevation. Use your smartphone level app, or just eyeball it.
IMPORTANT: Polarization Skew

You should also adjust the skew of your dish roughly according to what https://www.dishpointer.com/ says under "LNB Skew". For GOES-17 I had to point the antenna's left long edge (if facing the same direction as the dish) up at 45 degree angle.
8. Run goesrecv and perform fine antenna adjustments

goesrecv -v -i 1 -c ~/goesrecv.conf
This will show output every second that looks something like this:
...
2018-09-15T21:52:03Z [monitor] gain:  8.44, freq: -2121.4, omega: 2.589, vit(avg):  2400, rs(sum):  0, packets: 0, drops:  55

The vit(avg) stat shows the average viterbi error rate over 1 second interval (if running with -i 1).
If there's no signal, the vit value should be over 2000. When signal is stronger it should decrease.
This should help you point the antenna correctly. Slightly rotate the dish right or left and note whether the vit errors are increasing or decreasing.
Once you're at the local error minimum, perform the same process to find the minimum error rate while slightly adjusting the vertical angle.
When the vit errors are at their lowest, you've pointed the antenna. Double check the antenna position again with a compass to make sure you're pointed at the intended satellite.
If you can't pinpoint the signal even after precicely adjusting the antenna, flip the dish 90 degrees and try again.
9. Restart goesrecv and play around with the config parameters.

If your vit errors are under 400, and you're observing no packet drops, you're all set!
If the average errors are at around 1500-1800, try the following:


Terminate and restart goesrecv. This should allow it to readjust the gain and frequency offset to get a better read on the signal.


Cool the Raspberry Pi and the RTL-SDR dongle. I've noticed that temperature might significantly affect reception quality.


Play around with goesrecv.conf parameters. Try adjusting the gain and sample_rate. For the NooElec XTR or other E4000 tuners, you might need to set your gain to 10 or below.


Once you decreased the error rates, but your vit is still over 400, try making very slight adjustments to the antenna again.
10. Process packets into images

While goesrecv is running, in a separate session, run:
goesproc -c /usr/share/goestools/goesproc-goesr.conf -m packet  --subscribe tcp://127.0.0.1:5004
Once goesproc receives enough packets, it will start writing images and text to the locations described in /usr/share/goestools/goesproc-goesr.conf.
Writing: ./goes16/m2/ch13/2018-09-15/GOES16_M2_CH13_20180915T231750Z.jpg
Writing: ./goes16/m2/ch13_enhanced/2018-09-15/GOES16_M2_CH13_enhanced_20180915T231750Z.jpg
Writing: ./goes16/m2/ch02/2018-09-15/GOES16_M2_CH02_20180915T231750Z.jpg
Writing: ./goes16/m2/fc/2018-09-15/GOES16_M2_FC_20180915T231750Z.jpg
Writing: ./goes16/m1/ch07/2018-09-15/GOES16_M1_CH07_20180915T231820Z.jpg
...


11. TODO: Automatically restart goesrecv, store images on S3, send metrics to statsd and Grafana, and make videos!

Stay tuned!