Re: K3 APF

Posted by Bill W4ZV on Nov 13, 2010; 11:02pm
URL: http://elecraft.85.s1.nabble.com/K3-APF-tp5735159p5736422.html

KK7P wrote

> The APF algorithm is unchanged. Lyle is going to verify.

They are identical.

Maybe not quite identical.  The new algorithm is zero beat and the initial one peaked at +10 Hz above zero beat.  It could be that guys were not tuning to the actual peak so the residual ringing could have been several dB stronger than the signal (relatively) making one think there was more ringing.  Now the zero beat signal may appear stronger than the residual ringing (on noise) since it is better centered.  BTW the filter response measures about -4 dB at a 10 Hz offset, which is quite noticeable on weak signals.

I personally don't notice any difference but I had been peaking each signal using VFO-FINE in 1 Hz steps (which is how I found the +10 Hz offset in the initial version).  

73,  Bill