Class E – AM Transmitter
A Class C AM transmitter is a type of high-efficiency, solid-state transmitter that is popular among amateur radio enthusiasts. It is known for its simplicity, affordability, and efficiency compared to other types of transmitters. Unlike Class E’s switching operation, Class C amplifiers operate in a more “on or off” manner. The transistor conducts for a shorter portion of the input signal cycle (less than 180 degrees) and remains off for the rest. This allows for high efficiency (around 70-80%) in converting DC power to radio frequency (RF) output power – a crucial feature for powerful AM transmitters.
The transistor Q1 forms a simple carrier oscillator and Q2 is a buffer. The Mosfet U1 is a power amplifier, that provides around five watts. Due to its high efficiency, Class C amplifier U1 can generate significant heat, requiring proper heat sinking for good performance and reliability.
The coil details are given below,
L1 – 14 close wound turns on 0.5-inch air core using 16/18 wire, T1 – 230/6v power transformer as modulation transformer, L2 – 9 turns on T50-2 core using 30 wire or 13 turns on 0.25-inch air core using 30 wire, U2 – 16t/16t Airecore transformer, 0.5-inch dia air core. 6/18 wire.
Simple two-stage transistor one-watt AM transmitter
Simple series modulated AM QRP HF Transmitter