This circuit converts signals from the shortwave band to the 118 to 130 MHz VHF band used in aviation. The circuit uses a 55 MHz crystal. We found it in documentation from the 90s.
The circuit shown is suggested by National Semiconductor's Linear Applications Handbook. The base...
This circuit uses a pickup coil to take the signal from a telephone line without contacts. The circuit...
In this circuit, the transistors are NPN for general use and the phototransistors can be replaced by...