The diode is still required. The original cat's whisker diode was made with galena crystals. [[http://en.wikipedia.org/wiki/Cat%27s-whisker_detector]] Other materials are iron pyrite ("fool's gold", iron disulfide), silicon, molybdenite (MoS2), and silicon carbide (carborundum, SiC). It is also possible to use a rusty razor blade (iron oxide). | The diode is still required. The original cat's whisker diode was made with galena crystals. [[http://en.wikipedia.org/wiki/Cat%27s-whisker_detector]] Other materials are iron pyrite ("fool's gold", iron disulfide), silicon, molybdenite (MoS2), and silicon carbide (carborundum, SiC). It is also possible to use a rusty razor blade (iron oxide). |