Ed Engelken wrote:
The local oscillator is supposed to be below the signal frequency on
Band 4. All the S-40 series operate this way including the S-40B. The
LO is on the high side on the other bands. Make sure you are aligning
the LO on the proper side of the signal frequency.

Best Regards,

Ed

I heard about this earlier, when I first encountered problems with band
4 and I took this peculiarity into account when I did the alignments.