Transistor Radio with Diode powered by RF
This project is a radio with a transistor and a diode that uses RF power signal received from the floor to power transistor amplifier.
The signal which is detected by the diode is filtered by the capacitor 0.001 uF then used to perform three functions simultaneously: provide the DC to the collector circuit and provide the DC bias and the signal at the base of 2SC.
You'll love experimenting with different connections of antennas and different antennas as explained in other projects.
Try comparing this circuit with some simple circuits with crystal radios and radios with a transistor using a battery to power the transistor amplifier. After this comparison you should be able to conclude that you can not get something for nothing.