[Elecraft] CW Filter and Roofing Filter

[Wayne Burdick]

Hi Robert,

For best overall performance in CW mode with the K3S, I suggest using our 400-Hz 8-pole filter. The 250-Hz 8-pole filter is a further optimization, with very steep skirts to help with close-in QRM. 5-pole filters are also available but they won't have as steep skirts. (The 500-Hz 5-pole is not appreciably wider than the 400-Hz 8-pole.)

With either filter selected, high-performance, variable-bandwidth DSP filtering is applied within the crystal filter passband. As you adjust the bandpass controls, the K3S will automatically select the right crystal filter. The DSP filtering can go to as narrow as 50 Hz, and as wide as the widest crystal filter installed that is compatible with CW mode (up to 2.8 kHz, another one of our 8-pole filters.)

In addition, the DSP also provides a switchable audio peaking filter in CW mode (APF). This is a special filter type that can make signals very close to noise floor seem to emerge from the noise ("magically," some have said), without adding the ringing associated with traditional "brick-wall" filters. 

Other weapons in the K3S's weak-signal arsenal include CW REVerse mode, DSP and IF noise blankers, noise reduction, and both auto- and manual notch.

73,
Wayne
N6KR



On Jun 23, 2015, at 11:42 AM, rclark01 at comcast.net wrote:

> Hi all: 
> I currently own a Yaesu FT-950 and am considering selling it to move the the Elecraft K3S line. My question is about filters. My FT-950 has a roofing filter and a variable CW filter down to 200hz. Quite frankly, I can't tell much different when I switch in the roofing filter but the variable CW filter makes a big difference. I also have a 1970's TenTen Century 21 which has a 500Hz filter that, to me, seems to do a better job than the FT-950. So..when I read that a 500 Hz roofing filter is an option for the Elecraft K3S, what am I actually reading? Could there be a 500Hz roofing filter and a 500Hz CW filter or are they the same? In several Youtube videos, I've seen operators using the variable width the filter signals. What am I seeing? Are they adjusting the roofing filter or the cw filter? And...is the cw filter variable (like my FT-950) or fixed (like the Century 21)? 
> Thanks! 
> 
> Robert NJ4j 
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