Re: CW narrow filter


ve3ki
 

To start with, try just using the Width and Shift controls. You can narrow the DSP bandpass down to 50 Hz, independently of what roofing filters you may or may not have installed. See <http://www.nccc.cc/archived_meetings/pdf/K3%20Filters,%20Jan%202009.pdf>.

If you find that strong signals inside the 400 Hz filter bandpass but outside the narrower DSP bandpass are often causing AGC pumping or IMD problems that you can't eliminate with the Shift, Width and AGC controls, a narrower roofing filter might help. If you find you really need one, I'd suggest the 200 Hz filter, because the 250 Hz filter is actually not all that much narrower than the 400 Hz filter (333 Hz vs. 464 Hz at -6 dB, according to <http://audiosystemsgroup.com/K3FilterStudy-250HzRoof.pdf>). I believe that a lot of the difference seen by users who have both is primarily due to the narrower DSP width setting.

73,
Rich VE3KI


On Mon, Nov 26, 2018 at 10:46 AM, john ni0k wrote:
Operating the CW WW CQ contest makes me wish for something narrower than
the 400 Hz filter in my rig currently. I know Elecraft has a 200 Hz
filter but is there something else that people are using?

73,
-John NI0K

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