[Elecraft] K2 Filter attenuation?

[Ken Lotts]

I have spent hours tweaking the CW filters on my K2 and am not sure that
they are all that good yet.  (I am in no hurry to complete this radio, my
actual goal is to build a K2 that is comparable to the best).  I built a K2
five years ago and do not recall filter attenuation like what I am
experiencing on this new one..

To give you an idea what I am seeing I have posted a spectrogram screen shot
with all three filters superimposed on each other.  Does it look typical to
you?

CHART setup
=============
Center freq is 570 hz  (My favorite spot for CW)
AGC is OFF.
Noise source is a Palomar R-X Noise bridge.
Audio is measured from the headphone jack.
L34 is peaked

Chart can be viewed at http://www.vtc.net/~ken/filters.jpg

Here is what I have done so far.

1:  I have CAREFULLY inspected T7 ensuring that:

    a:  It has 20 turns red and 5 turns green

    b: Pin 3 is sourced from inner red wire Pin 1 is sourced
       from inner green wire (exactly as per diagram 6-18 in
       manual)

    c: Each of its solder joints are shiny and good.  I reheated
       them (twice).   There is no apparent PTTL

2:  Inspected X7 - X11  =

    a: Each are labeled 4.9136 - S (verified)

    b: Each have good shiny solder joints

    c: Each have two excellent ground connections (on each side).


3: Carefully peaked L34 with AGC off  (it peaked exactly one turn down from
the top)



Ken Lotts
aa7jc