Bei dieser Bauweise kommt keine Platine zum Einsatz. Das sollte auch mit einem Drahtverhau funktionieren. Wo ich schon einmal dabei war, wurde auch eine Frequenzskala mit beweglicher Markierung via Skalenseil in das Pflichtenheft mit aufgenommen. Die Chips waren gar nicht so einfach zu bekommen.

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Here is a candidate where all you need to do to modify a small FM headphone receiver is to desolder one end of two capacitors, and connect a short cable with an antenna connector. One 22 pF capacitor lifted on the right-hand side near the headphone connector for connection to the external antenna, and another one lifted on the left-hand side, above the volume control for increasing the tuning range The receiver IC is on the foil side of the board.

Find a simple pocket-size headphone FM receiver with tuning wheel not push-button search. See picture of complete radio below. Open it and check the FM receiver chip. It is a pin surface mount device with an FM receiver with a 76 kHz intermediate frequency. Although the TDA is specified for 1. Unsolder and lift the hot end of the 22 pF capacitor the end connected to pin 5. This receiver uses the headphone cable as the antenna. There is a coupling capacitor from the RF input on pin 12 which is connected to the headphone socket.

Unsolder and lift the headphone side of this capacitor, and connect the RF input via the capacitor to a BNC antenna connector. Now it is approximately MHz. Mine receives airport communications AM , amateur repeaters in the 2m band MHz , and some public service transmissions in the MHz range.

If I connect my TV cable, channel S9 sound If there are two active repeaters in the 2m band, only the strongest will be received. Both the Philips chips are specified for 1. I would be interested to hear from others who try to convert other single-chip FM receivers. I wrote in Sprat that I would be interested in hearing from others who try to convert other single-chip FM receivers. I have now made such a receiver myself also with success. This blog post was taken from the SPRAT article in order to enable discussions relating to the circuit.

The first comments are all based on emails I have received over the years with questions and comments, therefore you will see me as the author of these comments.

The BNC connector to the lower right is the new antenna connector. Posted by.





TDA7021 Philips, TDA7021 Datasheet


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