Found in a 1924 Gernsback publication this circuit uses 4 batteries for power and loop antenna. Listening is over a high-impedance type earphone or loudspeaker common at the time.
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...