Kalibrating device for GSM tapping

RTLSDR also allows us to view GSM traffic using a tool called kal or kalibrate-rtl. This tool can scan for GSM base stations in a frequency band. In this recipe, we will learn about using kalibrate and then confirm the channel in gqrx.

How to do it...

Following are the steps to use kalibrate:

1. Most of the countries use the GSM900 band. In the USA, it's 850. We will use the following command to scan for GSM base stations:

kal -s GSM900 -g 40

The following screenshot shows the output of the preceding command:

2. In a few minutes, it will show us a list of base stations:

3. We note the frequency; in our case, we will use 947.6 MHz along with the offset.

4. Now we open GQRX and enter it in the Receiver Options window:

5. We can see in the waterfall that the device is able to catch signals perfectly.

6. Now we will look at this data at the packet level. We will use a tool known as gr-gsm.
7. It can be installed using apt install gr-gsm:

8. Once it is done, if we type grgsm_ and press the Tab...