We found this circuit with JFETs in a Radio Electronics magazine from June 1969. The circuit has its assembly described in a complete article. Equivalent transistors can be used.
Found in a 90’s HAM Radio, this circuit is used for an optical communications system or even audio...
This circuit is from a 60's documentation. The capacitance C1 can be between 20 pF and 0.01 uF...
This circuit is from an old French documentation from the 70s. The coupler admits equivalents and...