[Elecraft] APF

[Wayne Burdick]

Gents,

Even *I* thought something had changed. (Lyle, our DSP engineer,  
assured me that it hadn't. The code hasn't changed.)

What's happening is that APF's effect is more obvious in the presence  
of certain band-noise conditions. These conditions will vary from band  
to band, and can change hourly, daily, maybe even monthly for a given  
QTH. I went back and listened the next day, and the APF was doing its  
job. I find it especially useful on the low bands, and many K3 owners  
have posted testimonials about this -- using the final version of the  
code.

The APF algorithm, with its gradual slope and ~30 Hz wide peak, brings  
up a very narrow portion of the audio spectrum (around the center  
pitch) just a few dB, without bringing up the adjacent noise or  
causing a rapid phase transition.

On several occasions I've measured a 3 to 5 dB improvement in S+N/N on  
weak signals using the K3's built-in audio voltmeter.

73,
Wayne
N6KR


On Jan 26, 2011, at 12:19 PM, juergen wrote:

> Hi Dave
>
> I asked the same question.
>
> The gurus at Elecraft indicated that nothing had changed. I still  
> have the original firmware and load it up in my spare K3. The  
> original version is the ESP version that works for me.
>
> I like you cant get the same results with the current release of the  
> APF that I go with the original. The original blew  my socks off I  
> was so impressed with it. I have done the comparison test  so many  
> times now  that I know that the original was the better release and  
> its not my imagination.
>
> If the programmer says the hex code is the same then there must be  
> some other factors at play. I dont really have  the answer.  I am  
> keeping the original firmware just for contests.
>
> 73
> John
>
>
>
> --- On Wed, 1/26/11, David Lear <delear at charter.net> wrote:
>
>> From: David Lear <delear at charter.net>
>> Subject: [Elecraft] APF
>> To: Elecraft at mailman.qth.net
>> Date: Wednesday, January 26, 2011, 11:27 AM
>> Did anything change with APF in the
>> latest release ?  Seemed to perform
>> better before rev 2.45. Maybe I 'm just loosing my touch.
>>
>> 73 Dave Lear NE5DL
>>
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