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 > _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
