This receiver was found in a Popular Electronics from the 90's. Its different configuration shows a tuning circuit after the tube that works as an aperiodic amplifier. Observe supply voltages.
We found this circuit in a 1974 integrated circuit manual. Operational amplifiers can be of...
We found this circuit in American documentation from the 1980s. Transistors can be of general use....
This sophisticated remote field strength meter circuit was found in a 73 magazine for radio...