Some care will need to be taken when soldering and when working with items like razor blades, etc. but the careful person should have no difficulty in constructing these using the plans I will outline.
The very first one, having only 2 parts to it.
Warning! This radio MAY NOT WORK in your area if there are no close by, strong stations. If you have a really close AM station, you may be able to get this to work. It is so simple though, that it is worth a shot.
First, find yourself a "piezoelectric" type earphone (not the magnetic and plate kind, they will not have the sensitivity needed).
Strip off the insulation (if there is a plug, it will need to be removed) from both wires.
Now, find yourself a 1N34A Germanium diode (low forward voltage, high sensitivity). solder the one wire of the earphone to the diode as in the schematic.
Now, tape (duct tape is good here) the other end of the diode to a water pipe (the facet at the sink is good), and grab the remaining free wire in your hand. You have now become the antenna, and the faucet the ground.
IF you hear anything at all, it should be a faint AM station.
There are 2 problems with this radio, actually at least 4 problems:
#1: it is not tunable, you can't "pick" the station you wish to listen to,
#2: it is not loud, IF you hear anything at all,
#3: it is not portable at all
#4: IF you have more then one station nearby, you will hear all of the strongest ones.