Re: APF For K3: progress report

Posted by Joe Subich, W4TV-4 on Oct 25, 2010; 8:08pm
URL: http://elecraft.85.s1.nabble.com/APF-For-K3-tp5671688p5672214.html


Wayne,

1) Outside the 30 Hz APF "peak" what is the background DSP
    bandwidth and can that be adjusted?

2) how does one prevent activation of a narrow CW filter (e.g.,
    200 Hz) and excessively narrow DSP filtering when activating
    APF?  Remember, the desired behavior is primarily to peak
    the desired signal while reducing the background bandwidth
    is a secondary concern.

3) How does one move the APF "peak" (as in the case of the
    old FT-1000D where the peak was tunable over most of the
    audio range0?

Rather that lose ability to specify basic DSP (and IF) bandwidth
when activating APF, I would suggest overloading the "notch"
control- particularly since auto notch (tap) does not function
in CW - to activate APF.

73,

    ... Joe, W4TV


On 10/25/2010 2:39 PM, Wayne Burdick wrote:

> We might have a field-test revision of K3 code that includes APF
> sometime this week.
>
> In this test version, APF is turned on by rotating the WIDTH control
> counterclockwise past the 50-Hz setting ("BW 0.05") to the 30-Hz APF
> setting ("APF 0.03"). This eliminates the need for a menu entry or a
> new switch function. A new DSP graphic pattern shows that APF is in
> effect. SHIFT can be used, with either 10- or 50-Hz steps.
>
> The APF filter is an "IIR" (infinite impulse response) DSP filter that
> accurately emulates the equivalent analog circuitry. There's a slight
> ring to the filter, as expected. Gain is also increased when APF is
> turned on, compensating for the loss of overall signal+noise that
> occurs at this very narrow bandwidth.
>
> 73,
> Wayne
> N6KR
>
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