Getting started with the RTL-SDR - Part 1: Finding stuff

Posted by Oz Hack on

So you got your hands on an RTL-SDR dongle... Now what... where to from here?

 

What this post is/is not:

 

You probably have done a bunch of reading about where to start and what you can do with the RTL-SDR . So sorry if this is a repeat of what you have read or totally useless to you but the intention of this series of posts is to give a starting point for SDR without being too technical and help you on your journey to do awesome things, so if this is too basic for you i am sorry.

If you are new to SDR like those of you i have spoken to at conferences or meetups then hopefully this serves as a great starting point for you.

 

What can i do with the RTL-SDR ?

 

Capture signals from your:

  • Roller door
  • Car keyless entry
  • Household wireless power meter
  • Next-door neighbours Your Doorbell
  • The list goes on..

How can i use this thing?

 

Lets talk about the easiest way to get you started..

Now you can use Linux, Windows or OSX for this but lets keep things simple. Kali Linux I find is pretty easy to use so lets start there. If you have never used Kali and are familiar with linux then awesome. If this is a struggle with this i would suggest some you-tubing on using linux first before continuing.

Note: In a VM the RTL-SDR works well and for the most part all SDR tools we sell work in a VM as long as the host PC is powerful enough.

 

Our tool kit:

  • Kali Linux (get your flavour here)
  • RTL-SDR dongle
  • GQRX
  • Something to sniff (I will use a wireless dog collar)

Setup your OS:

 

Go download Kali from the link above and fire it up.

Plugin your RTL-SDR and make sure it connects to the VM not the host machine.

Check the RTL-SDR device installed by running

root@kali:~# dmesg | grep rtl

 

Look for the return of something like :

Realtek RTL2832 successfully attached

 

Now lets update Kali and install GQRX

root@kali:~# apt-get update && apt-get install gqrx

 

After this downloads and installs we are ready to play. Run GQRX and setup your device

root@kali:~# gqrx

 

If asked to configure the device set your Sample rate to 1000000 otherwise if GQRX just opens then Click File > I/O Devices and set it up there.

 

Now you should see the below application open up, this is GQRX.

 

Click the power button on the top left and then watch the waterfall (The blue area) start to scroll down the page. Now you can change the Frequency up or down to adjust what you are listening to. As you change frequency you may notice some red or yellow signals flowing down the waterfall, this is what you are after! You may need to take some time searching up and down the spectrum looking for the signal so be patient, if you check out your device you may see an FCCID. If that is available then go to https://fccid.io/ and search for the ID there, you might find some interesting information about the frequency there that may help narrow down the search area..

Here is a example of what a wireless dog collar remote would give you if you set GQRX to the right frequency and press the button. Hold the button for a while and then press it fast and you will see the difference in the signal you receive.

And there you go, you got stuff..

 

Next Steps:

 

Record the signal and take a peek. If you stay in GQRX you will notice a red record button in the bottom right. If you leave all settings as they are and click record, press the button a few times and hold it down you can then stop the recording and close GQRX.

You will see on the command line something like:

 

Exact sample rate is: 1000000.026491 Hz

Recording audio to /root/gqrx_20170223_014744_433880000.wav

 

Now install Audacity, it is a free audio tool for most platforms

root@kali:~# apt-get install audacity

 

Run Audacity and open the WAV file you recorded, zoom in on the parts that look like data and take a peek, here is what i got.

 

Thats all for now, In the next post we will use another two different tools, inspectrum and osmocom_fft to capture the signal and look at the waveform