Weekend Project

Direct-Conversion Receiver with Two Transistors

Direct-conversion receivers are a joy to operate if they are well designed. The "2 BJT Receiver" has a single-balanced diode mixer, a tunable VXO, and a single-stage AF amplifier. Even a less experienced ham can build this receiver in about two hours.

A 40 m version is shown here. However, this receiver will work on any other frequency between 3 and 30 MHz if fundamental-mode crystals are used. If you use it on other frequencies, experiment with the values of the capacitive divider at the base of the oscillator transistor. With the values given here, it should perform well on 20, 30, and 40 m; just change the crystal for the other bands.

High-impedance headphones are mandatory. This receiver will not work with low-impedance headphones.