[Elecraft] K3: KRX3 question

[Brett Howard]

Direct quote from the message:

>Much of the narrowing is due to the very "humped" (Gaussian) 
>nature of the narrow crystal filters but the best responses 
>for RTTY seem to be with a roofing filter wider than 300 Hz 
>(the "250" Hz/8-pole) and/or keeping the DSP filter wider than 
>250 Hz with or without the dual passband filter.  Note: Ed uses 
>the "250 Hz" filter with his 200 Hz DSP setting. 

He says that the roofing filter needs to be wider than 300 and he thus
used the 250Hz filter with a 200Hz DSP filter setting.  Its simply put
that the roofing filter needs to be wider than 300 and he therefore uses
the 8-pole 250 Hz filter which it seems clear you know is 370Hz and
therefore fits the build of what is required.  Then behind that he has a
200Hz filter at the DSP IF.  

On Mon, 2008-07-07 at 16:35 -0700, Bill W4ZV wrote:
> 
> 
> Brett Howard wrote:
> > 
> > Being tha t it was mentioned that best responses seem to be with a
> > roofing filter wider than 300Hz and then he mentioned the "250Hz" filter
> > wouldn't you deduce that he meant the 370Hz filter which Elecraft calls
> > 250Hz?  I mean maybe I'm jumping to conclusions here but that was pretty
> > clear to me.
> > 
> 
> That's a good assumption but not what he said.  In other areas of his
> message, Joe was careful to say "250" (meaning Elecraft's nomenclature) or
> 370, but the what he actually wrote is:
> 
> "The consensus is that the 200 Hz DSP settings work as long as the roofing
> filter is more than 250 Hz wide."
> 
> I suspect much of this is academic anyway.  If you have an extremely strong
> signal 250 Hz from your center frequency, NO filtering is going to solve
> issues like the other guy's TX noise, although a narrower XFIL may sometimes
> help with desense.  At least on CW that's the advantage I see with the 200,
> but also remember that we also have a 50 Hz DSP in our ears which helps on
> CW (but not on RTTY).
> 
> 73,  Bill
>