Build a detector radio according to the circuit diagram

What you need:

• an empty toilet roll
• a roll of insulated copper wire (about 0.3 millimeters thick)
• about 20 meters of wire for the antenna and ground
• a capacitor 470 picofarads
• a germanium diode AA112T
• high-impedance headphones or earphones (e. B. a crystal earphone)

The detector radio and its function

The detector radio is one of the simplest radios ever. Accordingly, the circuit diagram is also very clear.

• Detector radios were, so to speak, the forerunners of the later tube radios and today's radio devices. In the early days of radio, they were often set up by people who wanted to take part in radio reception.
• The function is as follows: Every radio station emits so-called electromagnetic waves. These radio waves represent a form of energy.
• There is a coil in the detector radio. The antenna collects the radio waves, so to speak, and generates an alternating electrical voltage in this coil.
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• Through the diode connected to this coil (a so-called detector crystal was previously used for this, which is how the name of this radio comes from comes), the audio signals broadcast by the radio station are made up of this alternating voltage with a very high frequency (the radio waves) filtered out.


Build a radio yourself - this is how it works

With some knowledge of electronics, you can also use radios or transmitters ...

• This circuit also contains a capacitor, which is necessary in order to build up an oscillating circuit with this circuit. By combining the coil and the capacitor, this resonant circuit should vibrate at the same frequency as the radio station broadcasts its radio program.
• At the output of the circuit there is a small headphone which makes the radio signals audible.

How to assemble the receiver according to the circuit diagram

You can make the coil of the radio yourself, for example by winding the copper wire onto an empty toilet paper roll. Make a coil with about 40 to 50 turns.

1. The structure is quite simple due to the simple circuit diagram. First connect the capacitor to the two connections of the coil. Now you have a parallel connection of the coil and the capacitor.
2. Now connect the diode to one connection of this parallel circuit in such a way that its marking points away from the circuit (in the direction of the headphones connected below).
3. Now connect the headphones to the other connection of your resonant circuit as well as to the free connection on the diode (the connection with the marking).
4. Now you have practically set up the detector radio itself. To enable reception, you now need an antenna, which consists of a wire with a length of about 10 to 30 meters. This antenna wire is best placed outdoors. Just keep in mind that you should insulate the wire at the junction to secure it. Furthermore, you should not use the antenna outdoors during a thunderstorm.
5. Finally you need a ground for your detector radio. To do this, connect a wire to the other end of the oscillating circuit and to a grounded metal object (for example a water tap or a radiator).

You can also use different capacitor values ​​(or a variable capacitor) in this circuit to allow reception of additional radio stations.