A transmitter runs on DC (Direct Current) where as the electric supply present in our homes and offices is AC (Alternating Current). So first of all an AC to DC converter will be needed for the project. This can be done by building a rectifier or a convertor circuit. Use a step down transformer to convert the voltage to 50 Volts AC. Connect both ends of the step down with diodes and manage the load parallel to the diodes.
Calculate the required value of the capacitor to be attached in parallel with the load. If you want to avoid this first step you can always use a fabricated DC power supply to get the DC voltage directly.
The oscillator needs to be designed on paper before trying out anything. It consists of a small resistance connected in series with a capacitance. It produces oscillations and waves when alternating current is supplied to it, and an RC circuit primarily acts as a low pass filter.
Solder the copper wire with the ends of the oscillator or design a circuit board for this mini project. The oscillator runs on alternating current, but the circuit board overrides those waves with a signal which may be coming from any type of source.
For connecting a microphone with your PCB (Printed Circuit Board), buy a voice sensor from a nearby electronic store and interface it with the circuit board. The oscillator will need to be attached to an antenna to increase the range of the transmitter.