Anyone that has ever used the FT-1000 or the the FT-2000 knows exactly what the APF (or Contour setting as they call it) can do. It's an AMAZING tool to have in your tool box. With the FT-2000 you could choose whether you were going to Peak or Dip at the Contour freq. Furthermore, You could keep your filters set to ANY width you wanted to, and simultaneously Dip or Peak within the "Contour" / APF area. If you need any ideas on how this function should work than just refer to an FT-2000 or perhaps even an FT-5000 rig. It's very plain simple and clear. Which button it's put on is pretty much a "who cares", so long as it works.
As for the NR, I use that ALL the time, and I find that in my QTH it's a MUST have. There's FAR too much noise where I live, and with a constant S3 to S5 noise floor on 30 meters I rely HEAVILY on the NR to help me make things work out. The NB works well for me too, but the NR is far more important. I can only wish that I were one of you guys that lives where you have a perfect S1 noise floor and don't need your NR to work.
I've not once missed a weak signal using my NR by the way, because I know how to use it in conjunction with the RF gain and proper (for me) AGC settings.
> Date: Mon, 25 Oct 2010 17:01:14 -0400
> From:
[hidden email]
> To:
[hidden email]
> CC:
[hidden email];
[hidden email]
> Subject: Re: [Elecraft] APF For K3: progress report
>
> If you do it this way, how would you use it inside the 400 Hz roofing
> filter, where you wanted it to diminish somewhat toward the skirts of
> the roofer and then dive down. There would be no way of having this
> happen inside a given roofing filter other than the narrowest as the
> roofer is implied by the width setting.
>
> Would not be of any use at all on a running frequency. This only
> works as peak shaped audio to further narrow the very narrowest DSP
> selectivity. Personally I've never been disappointed by the 50 Hz,
> which is the cleanest narrow I've ever had in a RX.
>
> Not at all what I had in mind. With 400 Hz bandwidth and 500 Hz
> center, the passband INSIDE the roofer skirts is peaked at 500, loses
> about 10 db going down to 300 and up to 700, and at 300 and 700 does
> the normal roofer/DSP skirt sharp dive.
>
> This allows me to HEAR the off-freq caller, and either shift or RIT to
> center him, without the noise burden of a flat 400 Hz. Using the NR
> for this in a contest masks or loses really weak signals. Not yet
> discovered a setting that doesn't take away more than it gives. Never
> use NR on CW at NY4A on our K3's. Lose the whisper contacts just in
> the noise, any NR setting. Wouldn't even know they were there.
>
> Perhaps for this need a special NR setting that only shapes the audio
> without any cancellation at the noise level and several degrees of
> slope off?
>
> This is what I always meant by APF.
>
> Just my .02
>
> 73, Guy.
>
> On Mon, Oct 25, 2010 at 2:39 PM, Wayne Burdick <
[hidden email]> 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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