This transmitter operates in the FM band emitting beeps that can be picked up on a common radio at more than 100 meters in the open. The antenna is telescopic from 20 to 80 cm and the coil is formed by 2 + 2 turns of wire 28 in a form without a core of 1 cm in diameter. CV is a common trimmer with 10 to 40 pF of maximum capacitance. The circuit is from the book Science Fair Projects by Newton C. Braga.
