benfrog writes: "A company called Per Vices has introduced software-defined radio gear that Ars Technica is comparing to the Apple I. Why? Because software radio can broadcast and receive nearly any radio signal on nearly any frequency at the same time, and thus could "revolutionize wireless." The Per Vices Phi is one of the first devices aimed at the mass hobbyist market to take advantage of this technology."
We warn the reader in advance that the proof presented here depends on a
clever but highly unmotivated trick.
-- Howard Anton, "Elementary Linear Algebra"