Total posts : 45366
Your results from your sensitivity tests are interesting. I haven’t done much for AM but there is a nice way to align and test FM which is called SINAD. I modified a commercial receiver and fine tuned it and achieved a 12 db SINAD of .1 uV which is pretty “hot” for a VHF receiver.
Your suggestion of a coupling loop is good and as you pointed out calibration is difficult. As I mentioned, my receiver hears a 5 kW omnidirectional station 90 miles away so I don’t think it is on the low end of sensitivity despite its $15 cost. The thing that struck me was the vast difference in range using this compared to a car radio.
Good point about the car radio “peaking” cap. In the old days it was either behind one of the front panel knobs or on the chassis near the antenna connection. I don’t know if or where this is on modern radios but it sure made a difference when properly adjusted on the high end of the band.