Jim, I think you will find that it is true for the K3 because the roofing filter is selected by the DSP filter setting if you have the correct filters entered. You could, I suppose fool the software by entering the wrong filters in the setup, but the K3 will switch when the DSP setting crosses the roofing filter bandwidth. This may not be true for brands K,Y,I or T and I don't know about the K2, K1 etc. Willis 'Cookie' Cooke K5EWJ & Trustee N5BPS, USS Cavalla, USS Stewart
________________________________ From: Jim Brown <j...@audiosystemsgroup.com> To: elecraft@mailman.qth.net Sent: Tuesday, March 27, 2012 1:33 PM Subject: Re: [Elecraft] K3 Filter questions On 3/27/2012 11:12 AM, k.i...@comcast.net wrote: > I am pretty sure the DSP filter is effective only if it is narrower than the > roofing filter. Not at all true. When reading K6LL's comments, bear in mind that he is a VERY good operator and engineer. I value anything he has to say. I posted yesterday that I had done almost the same thing -- told the K3 that my 1.8 kHz filter was a 2 kHz filter so that it switches in at 2 kHz -- and that I was pretty pleased with the result. When there are multiple filters in any signal chain their responses combine (the proper engineering term is "cascade") so that the total filtering capability is that of both added together. This is most pronounced when two filters have approximately the same bandwidth and are set to the same frequency. The way this works is that if filter #1 is rejecting by 6 dB at a given off-frequency point and filter #2 is attenuating by 4 dB, the combined rejection will be 10 dB. This is approximately what K6LL and I are doing. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
