[Elecraft] Elecraft technology >> K2+

[Jim Brown]

On Mon, 29 Dec 2003 11:59:49 -0500, Floyd Sense wrote:

>My question is: does the KDSP2 auto-notch function degrade voice readability
>or does it function more like the MFJ?

Although I own a 599ZX that is hooked up to my Omni V, I have not used
its autonotch function.  

I like the KDSP2 a lot, and find that its autonotch is quite useable.
It does take a short time to lock in, and if you can leave it engaged
as you tune across the band, you will hear it unlocking on one carrier
and locking on another. I do not find that it seriously degrades
speech.

There is, by the way, a far better way to take out a carrier than a
notch, that has virtually NO effect on speech. That is to lock an
oscillator to the carrier, track its amplitude, and precisely match its
phase, then subtract it from the carrier. In other words, it nulls the
carrier rather than filtering it. The distortion of speech that you
hear with a notch is due to the extreme phase shift created by the
filter extending out both ways from the filter skirts.  In general, the
deeper and sharper the notch the greater the phase distortion. 

This nulling technique is well known in pro audio, but I don't know if
it has found its way into ham DSP. It certainly should -- it has the
potential to provide superior results if it can be pulled off well,
because it does not add phase distortion to the audio.  

Jim Brown K9YC