[Elecraft] [KX3] Oppopsite Sideband Null question - Redux

[Grant Youngman]

Elecraft Tech Support seems (understandably) a bit slow to respond at this point.   This is a repeat of a question I asked a few days ago.  Maybe someone else will see it and have some insight (?).

I have redone the opposite sideband null procedure in my KX3 (#8342) with KXFL3 filter board, using both the 2013 per-band null procedure, and the 2015 KXFL3 installation/calibration instructions.  The procedures are essentially the same, with a minor difference in RIT setting, and the fact that the KXFL3 installation manual calls this out only on 20M rather than on each band individually.

With my XG3 as a signal source,  I get an excellent opposite sideband null using either FL1 or FL2 bandwidth settings on all bands.  With narrow bandwidth and FL3 switched in, the null is very broad and shallow, and the opposite sideband is reduced only on the order of 10dB (+/-) rather than the very deep nulls (60+ dB) obtainable with FL1/FL2.  As a result, the opposite sideband remains clearly audible when tuning across a signal — say CW at 500 Hz bandwidth, etc.

If anyone else out there has done either of these procedures, did you get as deep a null with FL3 as with FL1/FL2?  I’m trying to determine if this is normal, or if there's an issue in the radio, possibly with my KXFL3 board.

Thanks … Grant NQ5T