This circuit was found in a 1945 publication. The circuit was stated to be part of a walk talkie. Note that, as it is a portable assembly, it was powered by batteries. The jack was for microphone insertion.
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...