What would really make me excited would be if Pi4 could eliminate the RTL-SDR altogether by doing the DSP via ARM Neon instructions.
Is it even close to being powerful enough?
Is it even close to being powerful enough?
All the DSP operations are already done by the Raspberry Pi.
http://aaronscher.com/wireless_com_SDR/rtl_sdr_info.html
In the diagram above, it shows “DSP” but that’s just two basic multiplications and a low pass filter. It doesn’t do any heavy lifting.
If you want to get rid of the RTL-SDR, you’d need that analog RF block and the AD converter inside the Pi. That doesn’t make a lot of sense of a general purpose SOC.
ADSB uses pulse amplitude modulation, so if you built or bought a downconverter and amplifier, you might be able to pick up the modulation by sending the downconverted/amplified signal to a GPIO pin and reading its state at say 5-10 MHz.
It'd be pretty messy and you'd have to write the demodulator from scratch, but might be able to pickup the frame decoding from one of the other products out there to actually read the content.
Would be a really fun project but not likely to save money and definitely not time.