radio without power supply?

Question

how to?????
Make a radio receiver **without using a power supply**. This can be done using an antenna coil, a tuning capacitor, a germanium diode that provides a low cut in voltage, and a high impedance headphone that won't load the circuit much. You can test your design with a high impedance headphone or an external amplifier with a high input impedance. If you wind your own antenna coil, you get additional credit. Your radio should be able to receive at least one station clearly.

Answer 1

This kind of radio is older than I am, and I'm well over 50 years of age. People were building these radios back in the 1920's and 30's.
Get a spool of #22, or 20 wire, 2 would be better. Take a Quaker Oats cylindrical box and close wind it from top to bottom with the wire. When I say close, I mean wire touching the wire next to it. The ends need to be held down with tape, glue, or hot glue. Wait until the glue dries before continuing. It's tedious, but the extra point will be worth it. You need at least 4 inches of free wire at the ends of the coil. Before you start all of this, get a piece of wood, 12 inches long, and at least 6 inches wide. A piece of 1x12 would be fine. Sand it smooth, and at least coat it with polyethylene. It'll help the project look nice, and give a firm foundation for everything. Connecting clips can be obtained from Radio Shack. Mount the coil on the board. Mount a variable capacitor at the edge of the board where the shaft can be easily turned. The vallue for this capacitor is going to be at least 365 pf. More than that would be okay, but not less. One wire from the coil connects to the frame of the capacitor. The other end of the coil connects to the rotor plates of the capacitor, as well as the antenna connection which needs to be a very long wire. 100 feet of wire for this antenna, and as high as possible would be great. At the antenna connection point of the coil and capacitor, connect the anode end of the diode. Connect one lead of the head phones to the Cathode end of the diode, and the other end to the frame, or ground side of the capacitor. Slowly turn the capacitor and listen for an AM radio signal. These radio receivers were used during WW2, and many other places where no power was available. I'm sure a Google search would turn up a schematic as would a search in at least the older Boy Scout radio merit badge books. Older being the 1950's to 1960's.
So far as the germanium diode is concerned, "cut in' really doesn't describe what the diode does. It rectifies the selected radio frequency into pulsating DC, which powers the head phones. Germanium is used because it has a conduction voltage of about 0.3 volts which makes it useful for this project. If you really want to "go for the gold", get a piece of lead ore (Galena). Connect it on one side to a conductive plate, this would be one side of the diode. The other side uses a fine piece of wire held in place and it's free end is used to find a conductive spot on the face of the ore which allows the radio signal to be rectified, and heard. That is the way it was done before diodes were invented, and there were no tube diodes available for signal detection. Good luck with the project, properly done, it will work. I have built one or two in my past.

Answer 2

crystal radio buy at kids shop Lance from Lacey Washington

Answer 3

Look up foxhole radios from WWII---GI's use to make their own with simple items they scrounged up and used no batteries.
http://ksharif.blogspot.com/2007/09/foxhole-radios-as-seen-in-wwii.html
http://members.aol.com/djadamson7/articles/foxhole.html