This detector was found in an old Electronic Design using transistors of the time. The circuit can be made with modern equivalent transistors. See the charts with your performance.
This circuit, obtained from the component manual used, has an ultra narrow 1 kHz range given by...
Mouser Electronics is providing the MGA-622P8 low noise amplifier for frequencies from 1.5 to 2.7...
This circuit of the 1970s uses Germanium transistors. Changes can be made to use silicon...