This post documents an experimental, complete, journey of building an AFSK APRS packet transmitter and receiver using the ADALM PlutoSDR software-defined radio, first in MATLAB and then in Python. I tried to cover everything from generating AX.25 frames, AFSK modulation, hardware connection troubleshooting on macOS, and finally a full packet decoder. What is APRS? APRS […]
This post is a Raspberry Pi 5 edition of our AFSK APRS transmitter and decoder project using the ADALM PlutoSDR. We cover everything from scratch: setting up the operating system, installing all dependencies including libiio, SoapySDR and pyadi-iio, connecting the PlutoSDR over USB, and running the full Python transmitter and decoder pipeline. What is APRS? […]
I was looking for a RF power module for my APRS beacon project and stumbled upon RF Parts. They are somehow of a niche–oriented online electronic part retailers, specialised on RF and — it seems — mostly on Ham Radio RF parts. I placed my order for two Mitsubishi power RF MOSFET Amplifier Modules and the package […]
While designing/ working on my APRS project, I used LTSpice IV for some simulations. For those that don’t know, LTspice IV is a high performance SPICE simulator, schematic capture and waveform viewer from Linear Technology. It is a freeware and can be downloaded from this link. Versions for my both platforms exist, Win 7.0 and Mac. […]
This is a quick update post. The road I took with this little project is slowly getting to a dead end due to what it seems to be a lack of available crystals for 144.8 (like 48.26 or 28.96 MHz, for using the third or fifth harmonic). I believe that, currently, all APRS modules are […]
More work today and yesterday on this project. Still locking on 144 MHz, but this is normal, the crystal I used is a 48 MHz overtoned, working on the third harmonic in this case, thus spot on 144.0 MHz: I managed to clean the output, at the expense of transmitted power. I used a 7-pole 2m bandpass […]
Been busy at work lately, but still had some time for myself. Latest idea: a low-cost APRS beacon, done with a classical 144.8 Mhz TX and a μController. AX.25 on air. Automatically. So these days I’ve been busy making this: Winding coils, soldering, measuring. Fun. The frequency is remarkable stable, given the rudimentary nature of this. For example, […]
