Adjusting the SatNOGS Client

2019-05-26T02:14:36Z

Cweiss: /* automatic adjustment via kalibrate-rtl */ I needed to install M4 and Automake in order to successfully run the bootstrap command on the current image.

(This page is a port of [https://community.libre.space/t/how-to-do-some-client-adjustments/1604/1 DL4PD's excellent post] to the SatNOGS forum.)

==Prerequisites / dependencies==

This page assumes:

*you've read all the [[Get Started|Getting Started]] page, as well as the pages linked under "Build" and "Operate" on the [[Main Page]]
*you've already made your [[Operation|first observations]] and have some waterfalls in the [[Network]]
*you've installed [http://gqrx.dk/download install gqrx] on your local computer.

==SatNOGS station adjustments==

Now you've come to a point where you want to know how well your station is performing. The first step is to determine your frequency offset.

===automatic adjustment via kalibrate-rtl===

As a more comfortable way to get the ppm of your SDR the tool ''kal'' from https://github.com/viraptor/kalibrate-rtl can be used.
At the moment you probably have to get and build it by yourself.

When using the pre-built image for the Raspberry Pi, you have
to install the following dependencies:
$ sudo apt-get install libtool pkg-config libfftw3-dev librtlsdr-dev automake m4

Then you can build and install it with
$ ./bootstrap
$ CXXFLAGS='-W -Wall -O3' ./configure
$ make
$ sudo make install

For usage, see available parameters:
$ kal -h
kalibrate v0.4.1-rtl, Copyright (c) 2010, Joshua Lackey
modified for use with rtl-sdr devices, Copyright (c) 2012, Steve Markgraf
Usage:
GSM Base Station Scan:
kal <-s band indicator> [options]

Clock Offset Calculation:
kal <-f frequency | -c channel> [options]

Where options are:
-s band to scan (GSM850, GSM-R, GSM900, EGSM, DCS, PCS)
-f frequency of nearby GSM base station
-c channel of nearby GSM base station
-b band indicator (GSM850, GSM-R, GSM900, EGSM, DCS, PCS)
-g gain in dB
-d rtl-sdr device index
-e initial frequency error in ppm
-E manual frequency offset in hz
-v verbose
-D enable debug messages
-h help

choose an appropriate band for scanning:
$ kal -s GSM900
Found 1 device(s):
0: Generic RTL2832U OEM

Using device 0: Generic RTL2832U OEM
Found Elonics E4000 tuner
Exact sample rate is: 270833.002142 Hz
kal: Scanning for GSM-900 base stations.
GSM-900:
chan: 33 (941.6MHz - 155Hz) power: 4877018.31
chan: 41 (943.2MHz - 208Hz) power: 2265226.87
chan: 43 (943.6MHz - 133Hz) power: 1287992.91
chan: 55 (946.0MHz - 179Hz) power: 1041611.46
chan: 57 (946.4MHz - 252Hz) power: 1405188.40
chan: 66 (948.2MHz - 13Hz) power: 5027059.56
chan: 79 (950.8MHz - 111Hz) power: 1088677.82
chan: 84 (951.8MHz - 231Hz) power: 945912.38
chan: 86 (952.2MHz - 212Hz) power: 2314696.93
chan: 116 (958.2MHz - 180Hz) power: 862935.90

choose a strong channel:
$ kal -c 33
Found 1 device(s):
0: Generic RTL2832U OEM

Using device 0: Generic RTL2832U OEM
Found Elonics E4000 tuner
Exact sample rate is: 270833.002142 Hz
kal: Calculating clock frequency offset.
Using GSM-900 channel 33 (941.6MHz)
Tuned to 941.600000MHz (reported tuner error: 0Hz)
average [min, max] (range, stddev)
- 206Hz [-293, -89] (204, 56.913998)
overruns: 0
not found: 0
average absolute error: 0.219 ppm

Now enter the measured ppm in satnogs-setup and you're done. The value should be entered without decimals, for example -1.

===manual adjustment===

To start, please connect to your Raspberry Pi's local web interface. By default the URL is something like "http://192.168.0.5:5000"; you'll need to figure out what it is for your client. In the upper right corner there is a big green button where you can set your ground station in standalone mode.

Here's how it looks in network mode:

[[File:SatNOGS_local_network_mode.png|center|600px]]

And here's how it looks when it's switched to standalone mode:

[[File:SatNOGS_local_standalone_mode.png|center|600px]]

Instead of using the standalone mode you can also stop and later start the satnogs-client service via systemd directly via the console:
<pre>
sudo systemctl stop satnogs-client
sudo systemctl start satnogs-client
</pre>

{{Message|
* Do not forget to set this back to network mode when done with your adjustments!
* While your station is in standalone mode, no observations from the SatNOGS network will be executed!}}

After setting to standalone mode, please SSH to your SatNOGS Pi with your well-known user account; by default, this is the user "pi". After successful authorization you will see a prompt like this:

<pre>
Linux satnogs190-dev 4.9.59-v7+ #1047 SMP Sun Oct 29 12:19:23 GMT 2017 armv7l

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Fri Jan 12 07:34:11 2018 from 192.168.10.35
pd@satnogs190-dev:~ $
</pre>

Now go ahead and start the "RTL SDR spectrum server":

$ rtl_tcp -a 0.0.0.0

If everything is fine, you will get an output like this:

<pre>
Found 1 device(s):
0: Generic, RTL2832U, SN: 77771111153705700

Using device 0: Generic RTL2832U
Found Rafael Micro R820T tuner
[R82XX] PLL not locked!
Tuned to 100000000 Hz.
listening...

Use the device argument 'rtl_tcp=0.0.0.0:1234' in OsmoSDR (gr-osmosdr) source to receive samples in GRC and control rtl_tcp parameters (frequency, gain, ...). No further output will be generated until you connect to this server. Hitting C-c will stop it and the command line appears.
</pre>

{{Message|You will have to stop this server if you want to go back to network mode - do not forget about this!}}

Now go ahead and start gqrx:

[[File:Startup_gqrx.png|center|600px]]

You will have to go to the setup menu, either by clicking on the "harde" symbol, or navigating through the menu item called "File -> I/O Devices"

[[File:Gqrx_io_configuration.png|center]]

Click on "Device" and chose "RTL-SDR Spectrum Server"
Edit "Device string" to match your Pi's IP address, Port defaults to 1234,
which is the same as the default setting for your server you just started on
the Pi.
Set "Input Rate" to something network friendly - we do not need the whole spectrum the RTL SDR is able to convert. 1,8 MSPS (1800000) should be OK
Depending on this setting your network will get very busy. Using wireless LAN is not recommended. Every sample has a data size of 16 bits, so the previous setting of 1,8MSPS/s results in a network load of 28,8 MBit/s:

<pre>1,8 MSPS * 16 bit/s = 28,8 MBit/s</pre>

"Audio Output -> Device" and "-> Sample rate" should be set by default,
values on average soundcards would be something like "Default, 48 kHz"
Close the dialogue by clicking "OK"
Your RTL-SDR spectrum server on the Pi should now show up a connection from
your computer running gqrx.

<pre>
client accepted!
set gain mode 1
set agc mode 0
set direct sampling 0
Disabled direct sampling mode
set offset tuning 0
set sample rate 960000
ll+, now 1
ll+, now 2
set freq correction 42
set freq 144500000
set gain mode 0
set agc mode 1
set gain 0
set freq 145814000
ll-, now 0
ll+, now 1
ll+, now 2
ll+, now 3
ll+, now 4
ll+, now 5
ll+, now 6
ll+, now 7
ll+, now 8
ll+, now 9
ll+, now 10
ll+, now 11
ll+, now 12
ll+, now 13
</pre>

The only thing left now is to "Start DSP" - from the menu item "File", by hitting C-d or simply clicking the Play-Button.

[[File:Gqrx_running.png|center|600px]]

Go for a known local HAM radio repeater or a CW beacon transmitter and set your demodulator accordingly. Narrow Band FM or CW is best to discover ppm error offset, which is the frequency offset in parts per million (ppm) which is always there with standard RTL-SDR dongles. It is also highly temperature dependent, so one might have to re-evaluate this from time to time. Enter the known frequency of your chosen transmitter (NFM repaeter or CW beacon). I have chosen a very known CW beacon just some km away from my home: ON4VHF on 144.718000 MHz. Walk through the tab called "Receiver options" and change the settings to fit the beacon: "Filter width Normal", "Filter shape Normal", "Mode CW-L", "AGC Medium". Set Squelch to something low, so you can hear noise from your speakers. Maybe you have to Adjust the audio "Gain" to something like "0.0 dB". You can adjust this to fit your needs to hear noise. With ppm error, which is default, set to 0.0 ppm, one can just guess where your receiver is listening. Anyway, just set it to 144.718000 MHz and try to find your beacon. You can see the result for my RTL SDR dongle down here:

[[File:Gqrx_ppm-error_offset.png|center|600px]]

Now got to the tab called "Input controls" and find an input field called "Freq. correction". By default this should show "0,0 ppm". Set frequency back to your beacons transmit frequency. After this you have to increase the Freq. correction value as long until you can hear the beacon. Now zoom into the panorama by locating your mouse pointer in the range where the frequency values are printed below the panorama, just above the waterfall. Try to fit the Freq. correction value as good as possible, that your receivers red indication line is just in the middle of the transmitters bandwidth.

[[File:Gqrx_ppm-error_corrected.png|center]]

Now write down the evaluated ppm correction value and exit gqrx as well as the RTL SDR spectrum server. In the command line now available start satnogs-setup:

$ sudo satnogs-setup

Navigate to "Advanced -> SATNOGS_PPM_ERROR" and enter the new value.

[[File:Fcecd26ca08cf3d23dffce719ef1dd13a4f7109d.png|center]]

Exit the satnogs-setup with "Back", then "Apply Configuration" (this might take a while) and "Back".

You are done with frequency offset correction.

{{Message|With gqrx, you get a nice tool to do some SDR stuff by the way. Just play around a bit and get familiar with all that stuff. Just keep in mind that, as long as you run the RTL SDR Spectrum server or you have set your client into standalone mode, nothing is done from network.}}

===adjustment using observations===
Another way of adjusting the frequency offset is by making an observation of a satellite that transmits CW. Once the observation is complete, the CW signal from the satellite should look like a straight line at 0Hz on the observation waterfall. If there's a frequency offset, the signal will be off-center. The image below shows observation details for a CW transmitter on VHF. Since the frequency offset is not yet adjusted, the CW signal is present between the -10kHz and 0Hz markers.
{{Message|It is possible for the CW signal to appear at a frequency above the 10kHz tick or below the -10kHz tick. In that case, use the frequency of the first tick with a higher absolute value frequency than the CW signal absolute value frequency. Do not forget to update the selected tick frequency in the equations below!}} 
[[File:Marked CW observation.jpg|center|800x800px]]
In order to compute the frequency offset, the waterfall image can be downloaded and opened with graphics editor like GIMP. After opening the waterfall image, vertical markers are placed on the -10kHz tick, the 0Hz tick and on the CW signal. Once the markers are placed, measure the width in pixels between the -10kHz tick and 0Hz tick, as well as the width between the CW signal and the 0Hz tick. The image below shows an example of the placed markers and the widths to be measured:
 
[[File:Measurement markers.jpg|center|550x550px]]
Let’s call the width between the -10kHz and 0Hz markers '''''widthTickTo0''''', and the width between the CW and 0Hz markers '''''widthCWto0'''''. From the example image above, we get the values '''''widthTickTo0 = 224''''' and '''''widthCWto0 = 131'''''. To compute the frequency offset, we compute the ratio between those widths and multiply by the frequency tick value as follows:
'''frequencyOffset = -10,000Hz * widthCWto0 / ''widthTickTo0'''''
In the case of the example above:
'''frequencyOffset = -10,000Hz * widthCWto0 / ''widthTickTo0'' = -10,000Hz * 131 / 224 = -5,848Hz'''
To compute the offset in PPM, divide the frequency offset in Hz by the transmitter frequency in MHz. In the case of the example above:
'''ppmOffset = frequencyOffset / transmitterFrequency = -5,848Hz / 145.725MHz = -40 PPM'''
The correction entered in satnogs-setup must have the opposite sign of that in the calculation, since we will be shifting the frequency in the opposite direction, making the SATNOGS_PPM_ERROR value:
'''SATNOGS_PPM_ERROR = 40'''
Note that if the CW signal is on the left side of the 0Hz marker, the PPM value is positive, otherwise, the PPM value is negative.
{{Message|Please keep in mind that it is possible for the CW transmitter to drift in some satellites. This makes the CW transmission an unreliable source in some cases. Make sure to double-check your adjustment with another CW satellite!}}

==Enhancements==

===Waterfall color improvements===

To get some nicer waterfalls one has to dig into waterfall plotting script. This is a static one and, so far, cannot be configured through satnogs-setup. Anyway: there is no magic behind it and one can understand what the changes are once you have seen them.

Log into the Pi and start at making a copy of /usr/share/satnogs/scripts/satnogs_waterfall.gp, just in case:

$ cp /usr/share/satnogs/scripts/satnogs_waterfall.gp ~/.

Now you can start editing the script:

$ sudo nano /usr/share/satnogs/scripts/satnogs_waterfall.gp

Search for a line starting with cbtics:

# Spectravue palette and scale
set cbtics (-110, -105, -100, -95, -90, -85, -80, -75, -70, -65, -60, -55, -50, -55, -40)

Comment it out by adding a #, copy, paste and edit that new line that it matches something like this:

# Spectravue palette and scale
#set cbtics (-110, -105, -100, -95, -90, -85, -80, -75, -70, -65, -60, -55, -50, -55, -40)
set cbtics (-90, -85, -80, -75, -70, -65, -60, -55, -50, -55, -45, -40, -35, -40, -25)

Now go ahead and find a line with cbrange:

set ylabel 'Time (seconds)'
set cbrange [-100:-50]

I guess, one already gets the point - change cbrange to match the new cbtics:

set ylabel 'Time (seconds)'
#set cbrange [-100:-50]
set cbrange [-85:-35]

Save the file and you are done. Schedule some observations and watch the new colors. Maybe you can just improve it a little more but keep in mind: always keep a bit of the noise floor into the waterfalls, so you can see the whole signals dynamic range. I love it, when there are only a few dots of the noise.

SatNOGS DB

2019-05-16T16:19:40Z

Cweiss: /* Docker Installation */ Updating documentation links to point to pages that exist.

__NOTOC__

[https://db.satnogs.org/ SatNOGS DB] is an effort to create a holistic, unified, global transmitter database for all satellite transmitters. You can export the data or even connect your application using our API. It's part of the SatNOGS project.

==Data==
The DB is open to everyone. Anyone is able to submit suggestions or use the existing Transmitters. All data are public and freely under the Creative Commons Atribution-Share Alike license.

==Contribute==

===Adding Satellites===
If you are a moderator you can add new satellites on the DB. For that follow the instructions:

#Log in to db.satnogs.org
#Navigate to https://db.satnogs.org/admin (if you are seeing a login screen, you are either not logged in to db.satnogs.org, or don't have moderator permissions)
#Click on Base::Satellite [https://db.satnogs.org/admin/base/satellite/add/ Add button]
#Complete the information to the best of your knowledge. Norad ID and Name are mandatory. Add multiple names on the "Names" field.
#Click Save and you are done!
#You can now move on to the next steps: suggesting and approving transmitters for this satellite.

Note: this process may change in the future; see [https://gitlab.com/librespacefoundation/satnogs/satnogs-db/issues?milestone_title=Improved+User+Experience the Gitlab issues list] for details.

===Suggesting transmitters===
Detailed instructions on suggesting transmitters can be found [http://docs.satnogs.org/db/contribute.html here].

===Approving transmitters===
If you are a moderator you can approved suggestions for transmitters. For that follow the instructions:

#Log in to db.satnogs.org
#Navigate to https://db.satnogs.org/admin (if you are seeing a login screen, you are either not logged in to db.satnogs.org, or don't have moderator permissions)
#Click on Base::Suggestions
#Click on the suggestion you want to review and carefully check the data, especially the citation URL
#When you are ready to approve or delete the suggestion, go back to the [https://db.satnogs.org/admin/base/suggestion/ full list of suggestions]
#Select the suggestions you want to act upon and from the drop down above either approve them or reject them
#You are done!

Note: this process may change in the future; see [https://gitlab.com/librespacefoundation/satnogs/satnogs-db/issues?milestone_title=Improved+User+Experience the Gitlab issues list] for details.

===Coding===
Fluent in Python and/or JS? We need you to help with the satnogs-db web application! Take a look at our [https://gitlab.com/librespacefoundation/satnogs/satnogs-db source code], or visit our [https://gitlab.com/librespacefoundation/satnogs/satnogs-db/issues? issues tracker] to start filling bugs, feature requests or code fixes for existing ones.

==API==

The SatNOGS DB API is available to anyone at https://db.satnogs.org/api/
More docs to come....

==Installation==

===[https://docs.satnogs.org/en/stable/satnogs-db/docs/installation-docker.html Docker Installation]===

===[https://docs.satnogs.org/en/stable/satnogs-db/docs/installation-virtualenv.html VirtualEnv Installation]===

SatNOGS Wiki - User contributions [en]

Adjusting the SatNOGS Client

SatNOGS DB