Hi John,
Thanks for the data. I will look into them.
I was reading a lot during the work commute (2x 45 minutes in public transport here in Prague every working day). I think I can increase the resistor values loading the detector diodes significantly, up to 100kOhm - 200kOhm. This will change the compensation curves again.
I am sure the compensation circuit would work, but this design of mine is an exercise in minimalism, and the op-amp would add to the size, price and current draw of the circuit.
My goal is a tiny back packing end fed tuner which will just work, no worries about the battery or cables to battery. I am not excited about the temperature dependence which would likely be compensated for by the circuit you suggested, but I can live with it.
Vojtech
