Circuit panel

One Transistor Radio

Here
is a simple circuit for a one transistor Audion type radio powered by a
1.5 V battery. It employs a set of standard low-impedance headphones
with the headphone socket wired so that the two sides are connected in
series thus giving an impedance of 64 Ω. The supply to the circuit also
passes through the headphones so that unplugging the headphones turns
off the supply. Using an Audion configuration means that the single
transistor performs both demodulation and amplification of the signal.

The
sensitivity of this receiver is such that a 2 m length of wire is all
that is needed as an antenna. The tap on the antenna coil is at 1/5th
of the total winding on the ferrite rod. For details of the antenna
coil see the article Diode Radio for Low Impedance Headphones. This
circuit is suitable for reception of all AM transmissions from
long-wave through to shortwave.