We found this circuit in documentation from National Semiconductor. For the medium wave range the coil consists of 50 + 50 turns of wire 28 in a ferrite rod.
This circuit was found in a 80's Popular Electronics. The sensor can be any phototransistor. The circuit is...
Found in old documentation, this circuit makes use of amplifiers of the time, uncommon today. Next...
This circuit is from an 80's documentation. Equivalent transistors can be used. The circuit is...