"Turn any raspberry pi into an SDR"
... by adding hardware to it. The headline made me at least think it somehow uses the pins as antennae, also because people have done this sort of thing in the past.
Same. Here's a Pi-based FM transmitter that uses no additional hardware except for an antenna:
http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Raspb...
They do work - transmit audio over the FM waves, but sadly the quality (buzzing noise) is far from expectations. Initially, I thought it is just my Raspi 3B, but when dived into the issues section on GitHub, I noticed more people were claiming they had similar problems. Do you know what could cause such degradation? Is there any better solution to transmit FM in a home?
Worrying fact is it also spams close ranges making them unable to listen. Have you applied any filter making it more stricter about the wave range it will take?
[0]: https://github.com/ChristopheJacquet/PiFmRds