Concerning the poor (2X 2nd I.F.) rejection, 2nd LO leakage back into
the 1st mixer can also cause this problem. I remember this problem with
the first dual conversion receiver that I built, and it wasn't until I
shielded the 2nd LO that things cleared up. Using radio chips with
micropowered oscillators solved that problem, along with my going to SMD
components.

Pete