Am Oscillator for Wireless Microphone

A 74HC14 hex Schmitt inverter’s gates are wired in a series using a 1MHz crystal that ultimately completes the loop. The spare gate’s input is connected to an intermediate output and a 220-ohm resistor is then connected from the gate’s output to AV.

An antenna is then connected to the intersection of the resistor and the gate output. Four twelve volts AA cells in a series serve as the power supply is put after a carbon microphone that is gotten from an old telephone handset. In addition, since the microphone varies the oscillator’s available voltage, modulation then occurs. Of importance is the fact that the crystal oscillator will keep running at a constant frequency.

Moreover, each time the oscillator switches, the 220 ohm sink resistor ensures that there is always a severe current gradient. It is important to note that this will not be picked up on a digital tuner since broadcasts are on 1MHz whereas digital tuners go up to 9 kHz in multiples.