TV Schematic

How can I make an AM wireless microphone? Can you suggest a website to find such schematic diagram for that?

Our instructor in Electronics engineering gave us a project, that is, to make a wireless microphone that will transmit in AM bandwidth. Because this is our first design project, I don't know where to start. I even search the web for schematic diagrams for an AM wireless mike, but I couldn't find any, instead, only FM wireless mike.

Public Comments

1. that because fm is far more superior than am transmittion.
2. An AM transmitter is just an oscillator whose output strength can be varied in response to some modulating signal (in this case, audio from a microphone). The simplest one-IC transmitter is this: Wire five of the gates of a 74HC14 hex schmitt inverter in series, with a 1MHz crystal completing the loop. Connect the input of the "spare" gate to one of the intermediate outputs and connect a 220 ohm resistor from the output of this gate to 0V. Connect the antenna to the junction of the gate output and the resistor. Connect a carbon microphone (from an old telephone handset) in series with the supply (4 * 1.2V AA cells in series). Modulation comes from the fact that the mic varies the voltage available to the oscillator (but the crystal oscillator keeps running at a constant frequency). The 220 ohm sink resistor is there to ensure that there is a severe current gradient everytime the oscillator switches. Note: you will not be able to pick this up on a set with a digital tuner, because it broadcasts on 1MHz and digital tuners only go up in multiples of 9kHz.