I remember playing with this back in college. IIRC it works by using a GPIO pin that’s normally used for outputting a pulse width modulated signal. By frequently (and cleverly) changing the duty cycle it is able to output something that looks somewhat like a frequency modulated signal.
yes I think so - and thanks for the links - the history of pulse width modulation is an interesting read. It’s also quite convenient that the pi outputs a signal at 100MHz by default, right in the middle of the commercial FM band
According to this wiki you can transmit stereo and set frequency from 1 to 250Mhz (FM)
What hardware would you need to increase its range? Just a bigger cable?
Rigging up a transmission cable (coax) to an outdoor antenna would make a difference but at the RF output power levels that the pi could produce (milliwatts), it would likely be unable to broadcast further than your immediate neighborhood without some kind of RF amplification.
To make something to rival Kurupt fm you’d be better starting with something more substantive - this site has some interesting stuff.
editing to add comment from the wiki that is referenced in the article: “When testing, the signal only started to break up after we went through several conference rooms with heavy walls, at least 50m away, and crouched behind a heavy metal cabinet.”
That’s better than I would have expected with an indoor piece of wire. With a very short transmission line to a correctly designed outdoor antenna, it could probably be heard a mile or so away.
