[Elecraft] K3 Roofing Filter Gain Setup

[goldtr8 at charter.net]

Dear All

I am looking at PSK31 signals not SSB and my definition of distortion is 
my visual observation on the PC waterfall in DM780 and the fact that 
decode of the signal by the PC starts to fail when I engage the narrow 
filters.   This is observed when I have clean signals using the 2.1 or 
2.7 filters and only DSP.  I do understand the how strong signals can 
create havoc in the band which is why I have the narrow filters.  The 
issue is until I get them setup to work well without interference I will 
not expect them to help much when I have close signals or weak signals 
that I want to pull out.

I do have all the offsets per the documentation with the filters so this 
should not be the issue.

Folks have pointed to some articles regarding the setting of the filter 
gain and have privided insight on how to use information on the K3 
display to help quantify signals.

My biggest problem is I have zero results when I do searches on these 
types of topics.  One of the responses was a link directly to a writeup 
that I had been searching for, go figure. :-)

All I know for sure is that again the user community has helped me get 
to the info I needed and now I have a basis of logic on what I will be 
looking at when I make some adjustments.

Now I need to get in front of the radio and follow the advice of the 
wise ones.

Thanks Everyone!!!


Don
KD8NNU


On Sat, May 28, 2011 at 3:17 PM, goldtr8 at charter.net wrote:

> Gents,
>
> I am searching without much luck for recommendations for the gain 
> setting recommendations for roofing filters.
>
> Specfically I have a 700 hz 8 pole and a 200 hz filter 5 pole.   There 
> is a gain setting in the k3 setup menue and I remember there were 
> recomendations on how to choose this setting.  However, I have not 
> been able to find reference on the net.
>
> Please can anyone provide some guidance as the performance when these 
> filters are engaged with digital modes is rather disapointing.    What 
> I mean by this is that a signal can be very clean with the 2.7 or 2.1 
> filter engaged but if  I use on of these filters the signal becomes 
> very poor.  I want to use these to isolate close in signals but there 
> appears to be a lot of distortation so they are basically of little 
> use.
>
> I am betting that there is more to this gain setting than meets the 
> eye and that is where my problem is.  I have put the gain for these 
> two filters at 1 and the 2.1 & 2.7 at zero.
>
> I will be playing around with the settings, but there is a method to 
> set this parameter so I need to learn what and why so I can make them 
> work the way they are supposed to work.
>
> Thanks and have a great holiday.
>
> Don
> KD8NNU
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