[Elecraft] How to outfit a K3 for JT65HF or JT9

[Don Wilhelm]

Phase noise is *not* the problem/solution being discussed.
It is the phase *shift* through the filter.  That is signals (within the 
passband) of one frequency are not delayed by exactly the same amount of 
time as signals of another frequency.  That is a different 'animal' than 
phase noise.

All filters will have some phase shift. but the better filters will have 
minimal phase shift within the flat portion of the passband. As you get 
closer to the slope (edges) of the passband, the phase will shift 
rapidly as the frequency changes.

The point is - to avoid large phase shift distortion, keep the filter 
width as wide as possible given consideration for reducing large signals 
by shifting the filter or otherwise moving the offending signal outside 
the passband.

Yes, there is often a compromise that must be made in the real world of 
operating.

73,
Don W3FPR

On 4/21/2014 3:25 PM, N7RJN wrote:
> Phase noise is an issue, however, adjacent signals in the filter passband
> seem to have more of an impact on the ability to decode weak signals than
> the phase noise associated with narrower filters.  I have been able to
> decode weak DX stations with 400Hz and even 250Hz filters that I could not
> decode at all with wider filters.
>
>