I have observed (while monitoring mixer output with an oscilloscope
during rf alignment) that the output of the mixer is, at zero beat,
about one half of what it is a few KC away from zero beat on all
bands. I have successfully performed IF and BFO alignment several
times (with the same result each time) and the natural crystal
frequency is 455.9 KC.

To me this suggests that the mixer is putting out a signal that is
different than the IF frequency, and thus I am losing some
sensitivity.

Can anyone suggest if and how I should adjust the local oscillator so
as to get maximum signal strength from the mixer at the IF frequency?