This circuit is from an old publication from the 1970s. It uses transistors and germanium diodes but can be implemented with modern transistors. With a coil of 50 + 50 turns of wire 28 or 30 in a ferrite rod it operates in the medium wave range, but this coil can be changed to other ranges. The indicator is 50 or 200 uA and powered by a 9 V battery. Changes to the resistors may be necessary for operation with transistors such as BC558.
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