[cathoderay57]

I confess that I'm not sure that I properly understand the fault symptom. It would appear that while frequency calibration and signal strength are OK on SW & LW, the sensitivity drops off at the low frequency (long wavelength) end of MW. Am I right? If so it would be helpful to align the oscillator such that you can receive the tone at 500m when injecting an AM signal from the Sig gen at 500m (600kHz) albeit weakly. Then tune the receiver and the Sig gen up to the HF end of MW, stopping at a couple of points along the way, and advise how clear the tone signal is at each waypoint, and whether the wavelength on the receiver scale at each waypoint is within calibration. If everything sounds good apart from weak signals at 500m this could simply be that the coil(s) has/have lost Q owing to damp ingress. Hope that helps to clarify things ( for me, at least). Jerry