SDR

With the HackRF One it is posible to send a fake GPS signal to other devices.

You need the following parts:
– HackRF One (can also be a Chinese clone)
– External TCXO (as GPS needs high precision)
– Antenna (best is a dedicated GPS antenna)
– GNU Radio and HackRF tools

sudo apt install gnuradio libhackrf0 hackrf libhackrf-dev

Check if you see 0x01 with (means TXCO is installed):

hackrf_debug --si5351c -n 0 -r

1. Download the GPS-SDR-SIM software

mkdir GPS_SDR_SIM

cd GPS_SDR_SIM

git clone https://github.com/osqzss/gps-sdr-sim.git

2. Compile it

make

3. Get the current satellite positions from NASA
*New: Updated URL, 03.03.2021* (Thanks for the information Ye-Sheng Kuo)

1. Create an account on https://urs.earthdata.nasa.gov/
2. Make a file called .netrc with the following content:

   machine urs.earthdata.nasa.gov login <username> password <password>

   replace <username> and <password> with your credentials on Earthdata.

3. Change the file permission with

   sudo chmod 004 .netrc

   so that no one can access your username and password.

You can automate this with this script (inside an .sh file):

#!/bin/sh
day=$(date +%j)
year=$(date +%Y)
yr=$(date +%y)

curl -c /tmp/cookie -n -L -o "brdc""$day""0.$yr""n.Z" "https://cddis.nasa.gov/archive/gnss/data/daily/$year""/brdc/brdc""$day""0.$yr""n.gz"

uncompress "brdc""$day""0.$yr""n.Z"
echo "brdc""$day""0.$yr""n.Z"

4. Generate the signal file with the static position (coordinates) you want to send

./gps-sdr-sim -b 8 -e YOUR_BRDC_FILE_HERE -l 40.812800,-60.005900,100

5. Send the signal

sudo hackrf_transfer -t gpssim.bin -f 1575420000 -s 2600000 -a 1 -x 0

You can also generate routes in the form of an NMEA file with the Labsat simulator: https://www.labsat.co.uk/index.php/en/free-gps-nmea-simulator-software

More information: https://github.com/osqzss/gps-sdr-sim
Please use this responsively. Bear in mind that it can have an impact on other devices if you send it outside a closed circuit.

Wouldn’t it be nice to have an scanner that records interesting radio signals automatically? For example you could record whenever people talk on certain frequencies.

Prerequisites:
– You have Gqrx installed (Guide for Armbian here)
– You have an RTL-SDR attached and the sdr drivers are installed (= it works with Gqrx).
Tip: If the Rtlsdr doesn’t work with Gqrx make sure that under File>I/O Devices you have selected “Realtek RTL2838…” (or whatever is your version) and not “Generic RTL2832…”

Installation of Gqrx-Scan

1. In the terminal go to a folder where you want the scanner to be installed.
2. Install Pearl prerequisites

sudo apt-get install libnet-telnet-perl

3. Download the scanner script:

git clone https://gitlab.com/khaytsus/gqrx-scan

4. Open Gqrx and set bookmarks on the frequencies you want to check. CTRL+b opens the bookmark manager.

5. Under Tools click on “Remote control” to enable it and start the reception (play symbol). Play around with the Squelch setting on the right side until you hear the audio clearly (you could start with -40.0db).
6. Now, you can go to the folder with the scanner script

cd gqrx-scan

7. There are several options to use it:
A) Switch between your bookmarks every two seconds

./gqrx-scan --type gqrxfile --pause 2

B) Check your bookmarks and stay on a frequency if it receives a signal above a threshold

./gqrx-scan --type gqrxfile --pause 0.2 --wait --delaytime 0.2

C) Record the audio whenever it hears something

./gqrx-scan --type gqrxfile --pause 0.2 --wait --delaytime 0.2 --record

By default it stores the .wav audio file in the home directory. If you have sox installed you can listen to it by typing:

play YourAudioFile.wav

More information: https://gitlab.com/khaytsus/gqrx-scan