The XFIL button is my least favorite feature of the K3 user interface. I always use the knob to change the bandwidth — except when I accidentally don’t hold the button long enough when activating or deactivating the APF, which I do a lot.
Victor 4X6GP > On 21 Feb 2019, at 13:40, Ed G <[email protected]> wrote: > > Thanks Don. I will have to experiement more using the DUAL PB. I have that > button set up for APF right now. > --Ed— > > > Sent from Mail for Windows 10 > > From: Don Wilhelm > Sent: Wednesday, February 20, 2019 6:00 PM > To: Ed G; [email protected] > Subject: Re: [Elecraft] K3 XFIL Button > > Ed, > > Keep in mind that the DSP provides the ultimate filter width, the one > situation you asked about - roofing filter wider than the DSP filter is > already present - just set the filter configuration to "lie" about the > actual filter width, and the roofing filter will be switched in at a DSP > width that is wider than the roofing filter. > > The other (DSP filter wider than the roofing filter) does not make much > sense to me. Yes, in the filter configuration, you can tell the K3 that > the (for example) 400Hz filter is really a 600 Hz filter, then you have > accomplished what you desire. > > I do not have much use for the XFIL button and never use it. I let the > Width control (or HiCut/LoCUT for SSB) switch in whichever roofing > filter is appropriate and consistent with the DSP width I have selected > and it works well. > > The DSP filter width is a "brick wall filter" and you will not be able > to hear signals outside that bandwidth. > > Keep in mind the purpose of the roofing filters. In a crowded band, the > roofing filters keep strong adjacent stations from activating the > Hardware AGC which is there to protect the ADC from overloading. In > other words (again using the 400Hz roofing filter example), if you have > the DSP bandwidth set at 300Hz centered on [150Hz plus sidetone pitch = > 750 Hz], and you have a very strong signal at 850 Hz, you will not hear > the strong signal because of the DSP width, but it will activate the > hardware AGC causing the AGC to 'pump' and the receiver sensitivity will > be reduced as a result of that 'pumping' - even though you cannot hear > the signal. > > As an alternative, you might want to try turning on DUAL PB in the menu > which will give you a wider passband that is attenuated from the narrow > filter peak (or focus). I believe that will give you what you seek. > > 73, > Don W3FPR ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
