Raspberry Pi FM Stereo Transmitter...

[Nick]

As regards FM bandwidth; we often see the BBC spec of 15kHz bandwidth quoted, but how many dB down is it at that point? What sort of filtering is used, any phase EQ, turnover frequency, all that?

Analog is hard, but so is high-speed digital (which has many of the same issues as analog).

Of course you can use a fully analogue design, the point here is that it's a left field crazy idea that just happened to work...

Others then enhanced it for fun, adding RDS, pre-emphasis. DMA etc. 

Just a bit of fun and lateral thinking...