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Circuit 214: Detector receiver with amplifier
Setup information
Install the transistor, the diode, the two resistors, the fixed value inductor and the two ceramic capacitors as
shown in Fig. 2.214. The nine jumper wires come next. Last but not least connect the Piezo element. Check
the placement on the board again and only then connect the battery.
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. Use a long, freely suspended wire as antenna. A
ground connection as short as possible is made to a water line. For the capacitor in parallel to the fixed
inductance, you could preferably use a small 200 pF wire capacitor. Alternatively, experiment with all sorts
of parallel and series combinations using 10 pF, 100 pF or 220 pF ceramic capacitors. One of these combi-
nations 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. You will find that volume and selectivity
have significantly increased in our circuit compared to the previous version.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.214.
Components required:
1 x 2N3904 transistor,
1 x BAT85 Schottky
diode, 1 x 2.2 kΩ resis-
tor, 1 x 220 kΩ resis-
tor, 1 x 1 nF ceramic
capacitor, 1 x external
ceramic capacitor (see
Experiment for value),
1 x 1 μF electrolytic
capacitor, 1 x 10 μF
electrolytic capacitor,
1 x 220 μH fixed induct-
ance, 1 x Piezo element,
1 x breadboard, 1 x 9V
battery with clip con-
nector
Fig. 2.214: Detector receiver
with amplifier
239
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