Two different filters although both are activated by the DUAL PB hold-button, depending on MODE. In RTTY it is the Dual-Tone Filter, two 50 Hz DSP filters spaced 170 Hz apart. In CW, it is a two level filter with two widths, 150 Hz and 600 Hz as I recall. The passband of the 600 Hz filter is 20 dB down which provides the skirts to hear nearby signals without having them dominate the signal(s) you focus on in the 150 Hz filter.
As for the choice of roofing filter, it needs to be wider than 600 Hz. So, yes, a 700 Hz crystal filter would give the most DSP protection from strong signals outside the 600 Hz bandwidth. 73, Ed - W0YK > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of David Wilburn > Sent: Wednesday, 30 July, 2008 05:37 > To: Elecraft Discussion List > Subject: Re: [Elecraft] Dual PB filter > > It has really saved the day on a couple of RTTY QSO's. That > is the only place I have used it. > > David Wilburn > K4DGW > > > alsopb wrote: > > Anybody out there playing with this feature or actually > used it in a contest? > > What are your experiences? > > > > Playing with it yielded the following:. > > > > 1) Narrower CW filters can't be used (at least not my 400 Hz and > > narrower filters). The wings are outside the narrow filter > passband. > > 2) For me that meant the 1.8KHz roofing filter was used. > > > > It seems like that defeats the purpose of having a K3. In > a contest > > situation, I would certainly like as many rock crusher > signal outside > > the roofing filter passband as possible. > > > > It would suggest one might consider the 1 KHz roofing > filter, if you > > want to seriously use this option. > > > > If there existed some intermediate (say 700Hz) or variable roofing > > filter, what would it's width have to be to include the > wings and be > > used for dual PB filtering? > > > > de Brian/K3KO > _______________________________________________ > Elecraft mailing list > Post to: Elecraft@mailman.qth.net > 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 _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
