We found this circuit in a 1987 documentation. It is a multi-tester with neon lamp and LEDs operating with both low continuous voltage and high alternating voltage.
This circuit was obtained in an old documentation, receiving the medium wave range. L1 has 20 + 60...
This circuit is from an old documentation from the 70s, so the transistors used are not common....
We found this circuit in a publication for radio amateurs of 1976. The operational amplifier is a...