This converter has coils according to the reception and converted frequency bands. We found it in the October 1989 Radio Electronics magazine in an article that teaches its construction.
This repellent operates with frequencies from 30 to 45 kHz, serving for insects and rodents. The...
This circuit is from a publication from the 70s. The original text was kept. The medium...
We found this circuit in an old American publication. The transistors can be BC558 and diode 1N34....