# RTLSDR usage

# Index

## 1.Setup rtlsdr


By rtlsdr usually call RTL2832U chip based tv-tunners which
can be used for not just recievin DVB-T frequencies but much more
and yes price is ~$10 it mean that anyone can just buy and try
without "loosing" money.


### 1.1.Get sources


Main development repository is on http://sdr.osmocom.org/trac/wiki/rtl-sdr
on github you can find more repos with experminental 
features (https://github.com/keenerd/rtl-sdr).

Getting sources from git:
```
  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 

### 1.2.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 balcklist driver by creating file
in */etc/modprobe.d/* with content:
```
  blacklist dvb_usb_rtl28xxu
```
Next thing that could appear is permissions on rtlsdr usage when its pluged in.
To allow everyone to use create file in */etc/udev/rules.d/* with content:
```
  SUBSYSTEM=="usb", ATTRS{idVendor}=="0bda", ATTRS{idProduct}=="2838", \
  GROUP="adm", MODE="0666", SYMLINK+="rtl_sdr"
```

### 1.3.Check if works

How to test if rtlsdr works? Run one of commands:
  rtl_test

I like to run rtl_adsb as you can see there that something is recieved and
you see that everything "works":
  rtl_adsb

There should be line by line showing up some "hex" lines. If some data is showen
then adsb data from plains is recieved.

## 2.Collection of tools  


### 2.1.FM

Get some sound trancmited from FM radio stations.

```bash
  rtl_fm -f 96.3e6 -M wbfm -s 200000 -r 48000 - | aplay -r 48k -f S16_LE
```


### 2.2.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
```

### 2.3.ADSB

ADS-B ( Automatic dependent surveillance broadcast ) in simple words airplain
geoposition, speed, height and flight number broadcasting. You can recieve
this data and see how many plains is around and sometimes flight number.

rtlsdr have default one rtl_adsb programm but it shows only recieved 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 metrs:
```bash
  dump1090 --interactive --metric
```
Output:

```
  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
```


### 2.4.AFSK1200

Gqrx is graphical SDR software where you can travel across frequencies
and in real time search for some transmission.

  http://gqrx.dk/

It have builtin AFSK1200 demodulator or in simple words ham radio packets.
And you could try to see what people sending in tex around the world.

### 2.5. Multimon-ng

Support many digital transmission modes.

  https://github.com/EliasOenal/multimon-ng


### 2.6. Waterfall 

Here is few waterfalls for rtlsdr

  https://github.com/roger-/pyrtlsdr

It have demo waterfall and aslo thats is python bindings to libsdr that
could used for fast prototyping

### 2.7. rtl-entropy

  https://github.com/EliasOenal/multimon-ng

Project that make rtlsdr as entropy source, uses FIPS 140-2 standart to
verify that data is random enought to pass test.

## 3.Projects where rtlsdr used  

### 3.1.WebSDR

WebSDR probably best site where you can go and click on some radio reciever 
and liste what happends in some particular country. WebSDR site contains
about 80 radio recievers around the world that can be accessed trought web
interface. 
  http://websdr.org/

If you whant setup your own radio reciever read FAQ, prepare mail and send mail
after that you could recieve precompiled websdr software with is easy
to setup with rtlsdr stick.

## 4.Problems 

### 4.1.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.

# 5.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