Re: K3 APF

Posted by Bill W4ZV on Nov 14, 2010; 12:20pm
URL: http://elecraft.85.s1.nabble.com/K3-APF-tp5735159p5737366.html

wayne burdick wrote

Joe,

If Lyle is using the same algorithm as before, and your results are as  
indicated below (virtually a tie), I don't understand how you could be  
hearing a "lack of ringing" in the new revision. I simply cannot hear  
any difference myself, and I'm extremely picky. We have nearly 100  
people testing, and only two or three have perceived a difference, so  
given the statistical evidence, I'd suggest that background noise  
conditions are the variable here, not the firmware. Lyle has also  
completely reviewed the DSP implementation -- no change.

I also suggested the background noise issue to Joe.  The bands have been relatively quieter since the latest FW was released, and white noise (i.e. galactic) does not cause the same amount of ringing as impulse noise (i.e. lightning).  Therefore the quiescent state of APF may sound less "ringy" than before.

I listened to a very weak DS5USH on 80m this morning and the APF was very effective at bringing him out of the noise.  I also did a few measurements using the latest 5 Hz SHIFT.  The worst case attenuation (when off zerobeat by 5 Hz) is <0.5 dB which is probably less than most ears will detect.  However only ONE setting of SHIFT is optimum so you need to listen carefully when adjusting.

73,  Bill