WSPR (pronounced "whisper") stands for "Weak Signal Propagation Reporter". It is a protocol, implemented in a computer program, used for weak-signal radio communication between amateur radio operators. The protocol was designed, and a program written initially, by Joe Taylor, K1JT. Software is now open source and is developed by a small team. The program is designed for sending and receiving low-power transmissions to test propagation paths on the MF and HF bands.
WSPR implements a protocol designed for probing potential propagation paths with low-power transmissions. Transmissions carry a station's callsign, Maidenhead grid locator, and transmitter power in dBm. The program can decode signals with S/N as low as −28 dB in a 2500 Hz bandwidth. Stations with internet access can automatically upload their reception reports to a central database called WSPRnet, which includes a mapping facility.
We will mainly work on the receiving WSPR transmissions here but the Raspberry Pi can also be used as WSPR beacon.
An accurate clock is essential both for transmission, and decoding of received signals.
NTPsec is an excellent option if you want to run a Stratum 1 server on the Raspberry PI. This HOWTO gives complete instructions for building a headless Stratum 1 timeserver using a Raspberry Pi, a GPS HAT, and NTPsec. Total parts cost should be about $110. Beginner-level light soldering may be required.
It seems that the newest kernel includes a DVB driver for the dongle as a TV receiver. We do not require this for our purposed so we will create a config file to blacklist it.
$ cd ~
$ sudo apt-get install git git-core cmake build-essential libusb-1.0-0-dev libfftw3-dev curl libcurl4-gnutls-dev
$ cat <<EOF >blacklist-rtl.conf
blacklist dvb_usb_rtl28xxu
blacklist rtl2832
blacklist rtl2830
EOF
$ sudo mv blacklist-rtl.conf /etc/modprobe.d
$ git clone git://git.osmocom.org/rtl-sdr.git
$ cd rtl-sdr
$ mkdir build
$ cd build
$ cmake ../ -DDETACH_KERNEL_DRIVER=ON -DINSTALL_UDEV_RULES=ON
$ make
$ sudo make install
$ sudo ldconfig
$ sudo cp ./rtl-sdr/rtl-sdr.rules /etc/udev/rules.d/
$ sudo reboot
Now you should be able to run the rtl_test command to test as a non-root user.
Follow instructions to install rtlsdr-wsprd by Guenael (VA2GKA) at https://github.com/Guenael/rtlsdr-wsprd, here are the commands:
cd ~
$ git clone https://github.com/Guenael/rtlsdr-wsprd
$ cd rtlsdr-wsprd/
$ sudo make
Turn off HDMI to reduce local EMI
/opt/vc/bin/tvservice -o
You can test rtlsdr_wsprd after replacing your callsign and grid locator values in the following command:
$ ./rtlsdr_wsprd -f 14.0956M -c <your-callsign> -l <your-grid-locator> -d 2 -S
- Update and add the information in
environment.samplefile to/etc/environment. This makes the environment variable accessible to the scripts executed by cron.
CALL="K0DEV"
GAIN="-a 1"
LOCATOR="FM18jv"
WSPR_RECV_PATH="/home/pi/wspr-receiver"
LOGPATH="$WSPR_RECV_PATH/wsprd-log/wsprd"
RTLSDR_WSPRD_PATH="/home/pi/rtlsdr-wsprd"
- Add the entries in the
crontab.sampleby executing the commandsudo crontab -e