One of the smallest and simplest transceivers using a single 2N2222A transistor, based on an original design by PY2OHH. Here you have the 40m band version, with an output power of about 700mW. In the videos you have older versions where I was trying different things with extra parts, removed later on the keep it as simple as possible.

Now you have the updated design. I ended up changing the circuit a little from the original design, for easier adjustment of the TX/RX offset frequency, to remove the AM broadcast band interferences and improve the low pass filter. This transceiver does not work with high impedance headphones ( 2000 Ohm etc. ), as PY2OHH recommended an old telephone speaker with an impedance around 300 Ohm, or use it with an external audio amplifier with high gain. In the blog article you will find more detailed info.

There is also an improved version ( Pititico 2 ) with audio amplifier included into the circuit.

Read the BLOG ARTICLE