Multiband WSPR transceiver
Some interesting links on the Weak Signal Propagation Reporter (WSPR) protocol:
This project implements a standalone multiband WSPR transceiver with all the WSPR signal processing done by Red Pitaya in the following way:
- simultaneously record WPSR signals from eight bands
- use FPGA for all the conversions needed to produce .c2 files (complex 32-bit floating-point data at 375 samples per second)
- use on-board CPU to process the .c2 files with the WSPR decoder
- upload decoded data to wsprnet.org
With this configuration, it is enough to connect Red Pitaya to an antenna and to a network. After switching Red Pitaya on, it will automatically start operating as a WSPR receiver.
The transmitter part is disabled by default and should be enabled manually.
The FPGA configuration consists of eight identical digital down-converters (DDC). Their structure is shown on the following diagram:
The DDC output contains complex 32-bit floating-point data at 375 samples per second and is directly compatible with the WSPR decoder.
The write-c2-files.c program accumulates 42000 samples at 375 samples per second for each of the eight bands and saves the samples to eight .c2 files.
The recorded .c2 files are processed with the WSPR decoder.
The decode-wspr.sh script launches
curl one after another. This script is run every two minutes by the following cron entry:
The transmit-wspr-message.c program transmits WSPR messages.
A pre-built SD card image can be downloaded from this link.
The SD card image size is 1 GB, so it should fit on any SD card starting from 2 GB.
To write the image to a SD card, the
dd command-line utility can be used on GNU/Linux and Mac OS X or Win32 Disk Imager can be used on MS Windows.
The default password for the
root account is
To use the full size of a SD card, the SD card partitions should be resized with the following commands:
Configuring WSPR receiver
By default, the uploads to wsprnet.org are disabled and all the decoded data are accumulated in
To enable uploads, the
GRID variables should be specified in decode-wspr.sh. These variables should be set to the call sign of the receiving station and its 6-character Maidenhead grid locator.
The frequency correction ppm value can be adjusted by editing the corr parameter in write-c2-files.cfg.
The bands list in write-c2-files.cfg contains all the WSPR frequencies. They can be enabled or disabled by uncommenting or by commenting the corresponding lines.
Configuring WSPR transmitter
The WSPR message, transmit frequency and frequency ppm value can be adjusted by editing transmit-wspr-message.cfg.
Building from source
The installation of the development machine is described at this link.
The structure of the source code and of the development chain is described at this link.
Setting up the Vivado environment:
Cloning the source code repository:
Building a bootable SD card image:
Feedback and results
I would like to thank PA7T and DK5HH for their interest in this project, for the tests that they have done and for the valuable feedback that they have provided.
The following plots show the number of WSPR spots per hour decoded by the multiband WSPR receiver: