OK, I think the rust is starting to come off now. So if I inadvertantly shifted the input frequency to the filter with the cal control, say 10K (instead of the 100 that I was looking for) then the
signal will no longer go through the passband. SO whats the procedure for getting it back?
I think that the scope reading was over 45 MHZ, so I'll just adjust the calibration until I see it moving down,
Then I can find it with a dummy load and my IC7300 display.
What part of the circuit is the Cal from the Arduino actually shifting?