question regarding rectifiyng radio signals - do Ge diodes have a voltage drop?

[Weylin]

I've been confused for several years with my old electronic set schematics with the use of a Ge diode in the radio circuits, namely the one that uses no batteries.

How does a Ge Diode even rectify such a weak signal? Don't Ge diodes have a voltage drop of some degree? Certainly not as high as silicons 0.7v, but I would have thought that a radio wave would be far to weak to even induce a current through one at all.

 

[rohitkhanna]

well, a Ge diode has a lower voltage drop ~0.25 - 0.3v. However this does not mean that it cannot 'rectify' below this voltage. The value of the forward current will be Much greater than the reverse current even for lower voltages, but this is good enough to feed to a hi-impedance headphone or circuit.