[Elecraft] 250 HZ XFIL QUESTION

[Mark]

The below applies to cw mode only at this time.

I have a basic K3 2.7hz 100 watt unit.  Tonite I added an 8 pole 250 hz filter.  After
installation and software setup it appears that the filter does not work when I select
filter 2.  The radio was purchased assembled and the 2.7 hz filter is in slot one and
i placed the 250hz filter in slot 5.

However - if I select Dual Passband - the filter appears to work. The display shows both
filter skirts and the bandwidth of the received signal is obviously isolated by the narrow setting.

My questions are these:  Do I have to use dual passband to use the 2nd filter?  Does dual passband use some combination of main filter (2.7) and 250hz DSP filtering instead of passing the signal thru the first crystal filter and then the 250 hz crystal filter?  If I have the
K3 software setup correctly - if I select the 2nd filter - does this bypass the 2.7 hz filter and use the 2nd filter; and if so,  why would it appear that my 250 hz filter is not passing a signal in this mode while it appears that it's passing it in Dual Passband mode.

I'm aware that i've probably phrased my questions incomprehensibly, but I'm just wondering
if i'm getting any use out of my 2nd 250hz crystal, or if it's not working because of some software setup error i've made or whether it's defective.

Thanks - Mark (N5EAT)