[Elecraft] K3: Use of LP-Pan & Roofing filter interaction

[Edward R Cole]

Looking into refining my use of the LP-Pan on the 1st IF of the 
K3.  One artifact is that the spectrum of the IF has a gain dip at 
the center frequency which apparently is due to interaction of the 
2.8 KHz roofing filter that is also loading the IF.

I am wondering if I might be able to program the K3 to use an open 
xtal filter position when I am using the LP-Pan?  I do not use any of 
the K3 beyond the IF so loss of use is not an issue; all signal 
processing is via the LP-Pan and a Delta44 soundcard to the sw 
running in my computer.  I might have to add a resistor to provide 
proper impedance loading for proper gain levels to appear at the IF output.

The dip in gain of the spectrum makes that frequency unusable in my 
application so looking for solutions (that are not invasive to the 
radio).  One option is inserting a pin diode switch to isolate the 
roofing filter bank but that requires some RF designing and precise 
surgery on the RF board.

73, Ed - KL7UW