If I understand correctly what Rich is saying, it could be exemplified like this: "If you want e.g. a 2.1 kHz bandwidth to receive a digital signal, and use a 2.1 kHz roofing filter in addition to a DSP setting of 2.1 kHz, you may find that it won't decode as well as using a 2.8 kHz roofing filter along with the 2.1 kHz DSP setting." That reminds me of what I have sometimes imagined observing in receiving SSB. This may be just my imagination, but I thought the voice sounded bad if I set the DSP to the same width as the roofing filter. I have used the utility to make sure the roofing filter is always at leas slightly wider than the DSP setting. Since that change I have been much happier with SSB receive voice quality. Is this just in my head? Flames accepted. If I am right, it suggests that the crystal filters somehow have a negative effect on voice quality. My guess would be that this comes from phase non-linearity at the edges of the crystal filters. Haven't we heard that Elecraft checks/selects roofing filters to ensure minimal phase distortion? Of course, the phase distortion would negatively affect digital signal demodulation as well.
73, Erik K7TV -----Original Message----- From: elecraft-boun...@mailman.qth.net <elecraft-boun...@mailman.qth.net> On Behalf Of Richard Ferch Sent: Friday, March 22, 2019 4:06 PM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] K3/K3s filter setting with the K3 Utility Earlier I gave an example of a situation where you might choose to enable a roofing filter at a bandwidth wider than the bandwidth marked on the filter. I also gave a poor example of enabling a filter at a narrower bandwidth. Here is a better one: You use a variety of digital modes with different bandwidths, one of which happens to be the same as or close to the bandwidth of one of your roofing filters. You find that when that roofing filter is engaged, that particular digital mode does not decode as well as it does with a wider filter setting. You might find that changing the configuration to switch that filter in at a narrower setting allows that particular mode to decode well, without having a noticeable adverse effect on the next narrower bandwidth mode you normally use. The likelihood of all this happening in combination with an actual need for a tight roofing filter because of nearby very strong signals might be quite low, but there is at least a theoretical possibility of such a scenario. There are probably more likely situations - just pointing out that it is not impossible that someone might want to do this. The good thing is, the capability is there if you somehow find that you need it. 73, Rich VE3KI ______________________________________________________________ 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
