At 07:28 AM 10/15/2012, Edward R Cole wrote:
>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
Found the solution. Page 46 of the K3 manual: Enabling Receive
Filters. I added FL3 for the DATA-A mode. So now I can switch
between FL2 - 2.8 KHz or FL3 - no filter, as desired.
Testing with FL3 selected, I no longer see a gain dip in the center
of the spectrum display of the LP-Pan output. My guess it does not
affect Tx filter which should be FL2. I kept FL3 open for adding
future filters: FL1 - 13 KHz, FL2 - 2.8 KHz, and FL4 - 400Hz. FL5 is
also vacant. In the sub-RX only FL2 - 2.8 KHz is filled.
73, Ed - KL7UW
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