[Elecraft] APF For K3: progress report

[Ron D'Eau Claire]

The concept reminds me most of the very popular 1940's homebrew project the
"Selectoject" (QST November 1947). Operating at audio, it featured a
two-stage constant-output phase shifting amplifier the provided a variable
frequency response from wide to razor sharp tunable across a 300 to 6000 Hz
range as either a variable amplitude peak or a variable amplitude notch.
It's actually a very simple circuit involving only three stages.

Ron AC7AC 

-----Original Message-----
At 10:08 PM 26/10/10, you wrote:
>and APF should peak a portion of that IF area that I choose (like a 
>manual Notch filter does, but reverse)... Not move it around.  3 
>different things here...  Does it make more sense to you?
>
Like the old Heathkit Q multiplier, QF-1, peak or null option?

John
k7up