This began with wondering if AM modulation can be done without multiplication. (It's not very easy to make a precise multiplier.) It looks like the answer is yes. The RF source here is clipped to the audio source and its inversion, and the filter gets rid of the harmonics created by the clipping. UPDATE: better type of filter, although it's lost a bit of bandwidth as I'm not quite sure how to adjust this type. It's not far off, having a 7.5kHz limit where 8kHz would be more like the better AM stations.
