This ultra-simple FM tuner can pick up local stations with good sound quality and was found in a 1982 publication. Assembled with scrap material, it will not offer any difficulties for the reader used to working with high frequency circuits. The circuit is shown in the figure. The connections between the components must be direct and short, giving preference to the version that uses a printed circuit board. L1 is formed by 2 turns of enameled wire 18 to 22, aligned with L2, which consists of 4.5 turns of the same wire. The diameter of the coils is approximately 1 cm. The RF shock (XRF) is formed by approximately 50 turns of thin enameled wire (32) in a 100k resistor. The variable capacitor, for tuning, is the type used in FM, miniature, while the trimmer, common, serves to adjust the operating point of the receiver. Its supply voltage is only 3 V and the device must be connected to the input of a good amplifier, with the help of a shielded cable. The transistor originally used was the 2SA234. The author states that the BF494 should work satisfactorily, but with small changes in the values of some components.
