At the time my 20M Shirt Pocket Transceiver was built and an article published in QRP Quarterly, I received many suggestions for improvements and enhancements. One of those was from PD7SSB who sent along a modification for adding an S Meter and AGC circuit. No this is not an IF derived circuit nor is it like the W7ZOI hycas.
[Again if you have not built and used the circuit please don't send me comments that it is not this or that. It does work and you will have an S meter! I could have just as easily placed an S Meter on the face of the display BUT I did have this cool analog type vertical bar mini meter that was looking for a good home.]
There is one modification to this circuit and that is the 4.7K resistor was replaced with a 25K Ohm trim pot connected as a variable resistor. This change enables you to now adjust the attack level of the AGC -- when does it start working. Essentially the FET switch is clamping the audio input!