Raspberry Pi Pico-based WSPR beacon
During the last decade, some HAM radio enthusiasts are gradually shifting their activity towards weak signal digital modes such as PSK31, MFSK, FT8 etc. That happened because of expanding noise on the classical HF bands such as 40 or 80 meters. The weak signal digital modes can mitigate the problem.
The WSPR digital mode protocol is a powerful way to know how the signal of my HAM radio station propagates globally. Nowadays the common practice of utilizing WSPR is generating the signal using a PC equipped by a sound card and WSJT-X software. Next the audio signal is used as input of SSB transceiver. Often it is too much for people who are keen on HF radio and want to try to step into that hobby.
So, I’ve managed to devise the WSPR beacon, which can boast of quite low entry threshold. Minimally you need only a Raspberry Pi Pico board (a few $), a wire or a dipole antenna and the software.
The software of the beacon is available on the GitHub under the MIT licence and consists of the WSPR-related part of software and HF oscillator, which is `the heart` of the transmitter. Despite the fact that the oscillator is completely digital, it possesses a number of decent features: 23 milli-hertz frequency resolution and frequency range of 1.1 to 9.4 MHz which covers three HAM radio bands: 160, 80, and 40 meter. The HF radio-signal are available on the GPIO pin of Pico. The additional hardware such as external VCO with PLL isn’t needed. The PLL implemented in C and oscillator itself is devised on the basis of hardware PIO — a brilliant Pico’s feature.
Unfortunately, I can’t boast of a decent antenna. I possess only a peace of copper rope, sticking out my window on the second floor. Adding an amplifier of 80mW output power, based on 2N3904, equipped with LPF filter in order to comply spectral purity requirements, I’ve got an impressive results:
If you are interested in this project, please don’t hesitate to ask me about this matter. In addition, consider clicking a star on the GitHub project’s page.
I’m planning to go further with this interesting principle of building HAM radio beacons.
Cheers, Roman Piksaykin, amateur radio callsign R2BDY. QRZ page.