Simple AM Transmitter: 220pF Circuit Diagram & Build Guide

Circuit diagram:

Description

Few AM transmitters are simpler to construct than this model, due to its uncomplicated inductor design featuring a single turn. The inductor is implemented as a commercially obtainable RF choke, such as the Jaycar Cat LF-1536. To minimize the circuit's size, the standard tuning capacitor has been omitted, and 220pF capacitors have been utilized instead. Frequency adjustment is achieved by modifying one or both of these 220pF capacitors – increasing capacitance raises the frequency, while decreasing it lowers it. Q1 is configured with a 1MO resistor, providing a high input impedance and facilitating the utilization of a crystal earpiece as a cost-effective microphone.