Well, right now, the article only mentions a receiver. So you're half-way there, you just need to build a transmitter.
[1] http://sci-toys.com/scitoys/scitoys/radio/am_transmitter.htm...
[1] http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/relaxo... can't draw the one from the Art of Electronics here but this site captures it pretty well. The 'trick' is having a .85Thz transistor.