[Elecraft] New K2 #3338 kit arrived

[Vic Rosenthal]

Steve Ratzlaff wrote:
> 
> Hi,
> Just received my new K2 kit, s/n 3338 yesterday. Let the building fun
> begin!
> Has anyone tried INRAD's 8-pole 400Hz BW filter (SF 1.8) in theirs?
> (Filter #770)

Yes, I tried it.

I modified an SSB board so that the filter could be used as OP1 (it only had the
controller and a few other components, plus the filter).  I tried various forms
of grounding/bypassing, etc., but I never could reduce the 'blowby' around the
filter acceptably.  Although the skirts were sharp to a point, the ultimate
rejection was compromised by leakage around the filter.  I gave up on this
approach.

Next, I soldered small pieces of RG172/u to the filter in such a way that the
input terminal was entirely shielded, and soldered them to header plugs such as
are used by the SSB board.  Then this was plugged directly into the K2.  This
limits you to only one bandwidth selection, but you can set the BFO differently
to give you a passband tuning effect which is quite useful for QRM reduction. 
However, although blowby was less with this approach, it was still unacceptable
in my opinion.  

Ultimately I went back to the standard filter, which shows much less blowby once
the crystal grounding mod was implemented.  The INRAD filter sits in my junkbox,
waiting for someone to figure out how to fit it to the K2 in a way that will
fully realize its potential.

Vic K2VCO