Does the choice of diode for an AM radio matter, so long as its sufficiently biased? For example, will a 4001 work? Or maybe a high Vz Zener?
If you're talking about the diode for the simplest detector, you want one with low forward voltage, like a Germanium diode or Schottky. More at http://www.techlib.com/electronics/crystal.html#Diodes
Beware that capacitance may matter too. See Schottky diode as AM detector?