[Elecraft] APF vs 10 Hz DSP, why they don't sound the same

[drewko]

I have one of those old QF-1 filters sitting in a drawer. I bought it
new years ago. It was certainly a lot of fun notching a signal then
switching it to peak and narrowing it down. And a very effective
accessory for my rig at the time, a Century-21 which had no such
refinements. 

I should give it a try with the K3. It is kind of a pain because there
is no bypass switch in the unit: it has to be powered on to hear
anything. Also a noticeable AC hum which was apparently a standard
feature of these units.

73,
Drew
AF2Z


On Sun, 16 Aug 2009 13:03:37 +0000, Brian/K3KO wrote:

>Unlike the phone guys, most CW guys could care less about audio 
>distortion or quality for that weak one.  They just want to be able to 
>copy it.  The information is in the off's and on's, the rest doesn't 
>matter.
>
>The old QF-1 Q-muliplier had an advertised Q of 4000 @ 455KHz.  That's a 
>bandwidth of about 100Hz.  There was some skill requiring adjusting 
>several knobs to make it work for you.  Of course, any K3 implementation 
>would have to be knobless.
>
>73 de Brian/K3KO
>