This circuit was found in an ancient American documentation. With it is possible to double the frequency of a transmitter For the range of 6 meters obtaining 8 W. The circuit makes use of varicap.
This bass booster preamp is from an English publication (1966). We can mount it with more modern...
This circuit was obtained from a 1986 Spanish magazine Resistor. The magazine no longer exists, but...
This basic configuration can be found in a lot of articles on this site. In this case, the relay...