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Circuit 213: Improved detector receiver
Setup information
Install the diode, the fixed value inductor and the two electrolytic capacitors as shown in Fig. 2.213 fol-
lowed by the four jumper wires. Last but not least connect the Piezo element. Check the placement on the
board again.
You can significantly increase the sensitivity of the Piezo element by using a sound plate or even a sound
box. Read more about it in Chap. 1.2.3
Experiment
A detector receiver is the bedrock in radio technology. This receiver circuit was already in use more than 100
years ago. Its signature is that no battery is needed for operation. Receiver and headphone are merely pow-
ered by a wire antenna, which should be as long as possible. A ground connection as short as possible is
made to a water line. For the capacitor in parallel to the fixed value inductor, we recommend a small wire
capacitor (approximately 200 pF) that you may have in your crafting box. Alternatively, experiment with
all sorts of parallel and series combinations using 10 pF, 100 pF or 220 pF ceramic capacitors. One of these
combinations should offer favourable conditions for a clear reception of the nearest local broadcaster on
MW. At night you should be able to receive several other strong stations.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.213.
238
Components required:
1 x BAT85 Schottky
diode, 1 x 1 nF ceramic
capacitor, 1 x external
ceramic capacitor (see
Experiment for value),
1 x 220 μH fixed induct-
ance, 1 x Piezo element,
1 x breadboard
Improved
Fig. 2.213:
detector receiver
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