Luckily the FAQ already mentions why this is a bad idea.
> Please note that due of the hardware of the raspberry pi, harmonics ARE generated on 3x, 5x, 7x and 9x the desired frequency. Those harmonics are polluting important services like emergency services a d others.
Please do not use the GPIO of a Raspberry Pi to generate a high frequency to emit radio waves. Putting square waves on the air is always asking for trouble. A simple filter is not a proper solution if the source is so dirty.
For a project as well built of this seems, it seems odd that they would advice people to use such a hacky way. Syncing networked clients to play audio at exactly the same time is a solved problem.
Pi-FM-RDS, from which this project is forked, warns under its Warning and Disclaimer section that "In most countries, transmitting radio waves without a state-issued licence specific to the transmission modalities (frequency, power, bandwidth, etc.) is illegal. Therefore, always connect a shielded transmission line from the RaspberryPi directly to a radio receiver, so as not to emit radio waves. Never use an antenna." They literally warn users not to do what your project tells them to do. I can't be arsed to do the proper math but a casual check suggests that the output power from the Pi could easily exceed the FCCs low power FM transmitter exemption.
The project also cursorily mentions the need to use a bandpass filter to avoid interference but fails to explain the specific device needed or how to wire it up in the instructions.
Luckily the FAQ already mentions why this is a bad idea.
> Please note that due of the hardware of the raspberry pi, harmonics ARE generated on 3x, 5x, 7x and 9x the desired frequency. Those harmonics are polluting important services like emergency services a d others.
Please do not use the GPIO of a Raspberry Pi to generate a high frequency to emit radio waves. Putting square waves on the air is always asking for trouble. A simple filter is not a proper solution if the source is so dirty.
For a project as well built of this seems, it seems odd that they would advice people to use such a hacky way. Syncing networked clients to play audio at exactly the same time is a solved problem.
Pi-FM-RDS, from which this project is forked, warns under its Warning and Disclaimer section that "In most countries, transmitting radio waves without a state-issued licence specific to the transmission modalities (frequency, power, bandwidth, etc.) is illegal. Therefore, always connect a shielded transmission line from the RaspberryPi directly to a radio receiver, so as not to emit radio waves. Never use an antenna." They literally warn users not to do what your project tells them to do. I can't be arsed to do the proper math but a casual check suggests that the output power from the Pi could easily exceed the FCCs low power FM transmitter exemption.
The project also cursorily mentions the need to use a bandpass filter to avoid interference but fails to explain the specific device needed or how to wire it up in the instructions.