150mW Crystal AM Transmitter

Here is the circuit of a medium power crystal based amplitude modulation (AM) transmitter that can deliver 100-150mW of radio frequency (RF) power.

Four Stage FM Transmitter Circuit

Here's the circuit diagram of a four RF stage FM transmitter. The stages are, very high frequency (VHF) oscillator built around a HF transistor BF494, a pre- amplifier built around transistor BF200, a driver transistor 2N2219 and a power amplifier using 2N3866.

Circuit Diagram of  4 Stage FM Transmitter: Click  to enlarge

For complete explanation about this FM transmitter circuit, Download this document.

Note :

• This FM transmitter is only meant for educational purposes. The outdoor use is illegal.
• Assemble the circuit on a general purpose PCB and arrange the antenna without any disruption for getting the maximum range.
• Use a heat sink for transistor 3866.

Long Range IR Transmitter Circuit

Most of the infrared remotes work on the range below 5 meters. The complexity of the circuit increases when we have to transmit the IR to longer ranges say 10 meters. So you need to multiply the transmitted power into usually four times. This IR transmitter circuit will give you pretty long range.