My company is scientific consultant services, inc., hence the member name. However, I am really an independent inventor/scientist with more than 70 years of experience with electronics. I am also a ham radio operator (call sign AC2BQ) and a weak signal enthusiast. I do a lot of prototyping involving electronics, optics, and DSP. I am currently testing an SDR-based lock-in amplifier using a dual channel SDR. To get the extremely high blocking dynamic range needed, I am playing with various tuned preamplifiers, hence my first question: whether anyone has tried using a tuned amplifier as a front end, and an SDR as a lock in: I am curious whether anyone has had success with such an approach, and any issues they have encountered.