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|
title:Using RTLSDR
keywords:linux,rtlsdr,gqrx
# RTLSDR usage
## Setup rtlsdr
By rtlsdr usually call RTL2832U chip based tv-tunners which
can be used for not just receiving DVB-T frequencies but much more
and yes price is ~$10 it mean that anyone can just buy and try
without "loosing" money. None of examples below requires any modifications
or extra hardware to run.
As of 2022 the version r820t2 that is commonly available.
### Get sources
Main development repository is on http://sdr.osmocom.org/trac/wiki/rtl-sdr
on github you can find more repos with experimental
features (https://github.com/keenerd/rtl-sdr).
Getting sources from git:
```sh
git clone git://git.osmocom.org/rtl-sdr.git
```
I prefer using plain binaries without any kind of installation. Just
compile and use binary without any troubles.
Build:
```bash
cmake .
make
```
All binaries is in src dir.
| Util | Desc |
| --- | --- |
| _rtl_adsb_ | recieve plain ADSB plain packets |
| _rtl_eeprom_ | read |
| _rtl_power_ | log power over frequency range |
| _rtl_fm_ | demodulate signals |
| _rtl_sdr_ | output raw rtlsdr data |
| _rtl_tcp_ | remote rtlsdr server |
| _rtl_test_ | test rtlsdr |
### Drivers
Linux kernel have some drivers for rtlsdr stick and DVB-T. When you will plug
rtlsdr then kernel probably will load DVB-T drivers and you will not able
to use you rtlsdr for sdr. Way yo fix is it add some drivers to black list and
next time when you will plug rtlsdr this drivers will not be loaded.
Check if rtlsdr related drivers is loaded:
```bash
lsmod | grep rtl28
```
If there is some drivers then blacklist driver by creating file
in */etc/modprobe.d/* with content:
```bash
blacklist dvb_usb_rtl28xxu
```
Next thing that could appear is permissions on rtlsdr usage when its plugged in.
To allow everyone to use create file in */etc/udev/rules.d/* with content:
```bash
SUBSYSTEM=="usb", ATTRS{idVendor}=="0bda", ATTRS{idProduct}=="2838", \
GROUP="adm", MODE="0666", SYMLINK+="rtl_sdr"
```
### Check if works
How to test if rtlsdr works? Run one of commands:
```sh
rtl_test
```
I like to run rtl_adsb as you can see there that something is received and
you see that everything "works":
```sh
rtl_adsb
```
There should be line by line showing up some "hex" lines. If some data is shown
then adsb data from plains is received.
## Collection of tools
### rtl_fm, FM modulation
Get some sound transmitted from FM radio stations.
Find local radio station and set frequency choose wide band FM modulation __-M wbfm__
set SDR sample rate to any supported, but more then 150kHz, for example __-s 200000__.
Resample SDR output to audio frequency __-r 48000__. Pipe output to any audio tool
here is example for aplay where sampling rate set to same resampled rate of SDR.
IQ format from rtlsdr is signed 16 bit little-endian __-f S16_LE__.
```bash
rtl_fm -f 96.3e6 -M wbfm -s 200000 -r 48000 - | aplay -r 48k -f S16_LE
```
### rtl_power, Spectrum diagram
Scan spectrum to find some activities on different frequencies.
Good link with all description is http://kmkeen.com/rtl-power/ .
Main usage of rtl_power is :
```bash
rtl_power -f 76M:108M:125k -i 1 fm_stations.csv
```
and then draw image :
```bash
heatmap.py fm_stations.csv fm_stations.png
```
### rtl_adsb, ADS-B
ADS-B ( Automatic dependent surveillance broadcast ) in simple words airplane
geo location, speed, height and flight number broadcasting. You can receive
this data and see how many plains is around and sometimes flight number.
rtlsdr have default one rtl_adsb program but it shows only received data,
without any decoding. Here is dump1090 specifically for rtlsdr and nothing
more:
https://github.com/antirez/dump1090
description howto install could be found also here
http://www.satsignal.eu/raspberry-pi/dump1090.html
Using in interactive mode with height in meters:
```bash
dump1090 --interactive --metric
```
Output:
```text
Hex Flight Altitude Speed Lat Lon Track Messages Seen .
------------------------------------------------------------------------------
71be01 10052 1009 36.434 33.544 45 9 1 sec
424913 SDM6329 10966 711 36.440 33.405 221 65 0 sec
```
### GQRX, FSK1200
Gqrx is graphical SDR software where you can scan across frequencies
and demodulate and listen FM broadcasts and HAM bands frequencies.
Easy way how to explore the available frequency range
http://gqrx.dk/
It have built-in AFSK1200 demodulator or in simple words ham radio packets.
And you could try to see what people sending in text around the world.
### Multimon-ng
Support many digital transmission modes.
https://github.com/EliasOenal/multimon-ng
### Waterfall
Here is few waterfalls for rtlsdr
https://github.com/roger-/pyrtlsdr
It have demo waterfall and also thats is python bindings to libsdr that
could used for fast prototyping
### rtl-entropy
https://github.com/EliasOenal/multimon-ng
Project that make rtlsdr as entropy source, uses FIPS 140-2 standard to
verify that data is random enough to pass test.
### rtl_433
Generic ISM data receiver. Can use to track remote sensors, weather stations and many
other devices.
https://github.com/merbanan/rtl_433
```sh
rtl_433
```
## Projects where rtlsdr used
### WebSDR
WebSDR probably best site where you can go and click on some radio receiver
and listen what happens in some particular country. WebSDR site contains
about 80 radio receivers around the world that can be accessed trough web
interface.
http://websdr.org/
If you want setup your own radio reliever read FAQ, prepare mail and send mail
after that you could receive p recompiled websdr software with is easy
to setup with rtlsdr stick.
## Problems
### Sync errors
Once there was sync error when was trying to use rtl_test or rtl_adsb.
To fix that changes for better quality usb cable.
### More then 1 dongle
When you run you run usually more then 5 dongles you could get error saying
something about libusb error (-5) you need to decrease buffer as default one
is (16 * 16384) and it should work
```bash
rtl_test -b [NEW_SIZE]
```
thx goes to libera.chat/##rtlsdr chan
## Links
1. [http://kmkeen.com/rtl-demod-guide/](http://kmkeen.com/rtl-demod-guide/)
2. http://kmkeen.com/rtl-power/
3. http://sdr.osmocom.org/trac/wiki/rtl-sdr
4. http://www.rtl-sdr.com/
5. https://github.com/antirez/dump1090
6. http://gqrx.dk
7. https://github.com/roger-/pyrtlsdr
8. https://github.com/EliasOenal/multimon-ng
9. https://github.com/merbanan/rtl_433
|
