Matching antenna (CB7458E)

The coil and sockets of this circuit found in a QST depend on the frequency band that is intended to be tuned.

741 amplifier for phototransistor (CB25522E)
In the figure we have an amplifier using the 741 operational amplifier without the need for a...
Operational Wien Bridge Oscillator (CB12423E)
Found in a 1995 Hands On-Electronics, this circuit generates a sinusoidal signal whose frequency...
Current to frequency converter (CB9604E)
Found in a manufacturer documentation from the 90s, this circuit makes use of period components. The...