On 1/26/2012 11:08 AM, Nate Bargmann wrote: > I have had bad distortion using the Auto Notch onSSB.
ANY filter, whether it uses analog components or DSP (which is a simulation of analog components) has a phase response associated with the amplitude response, and the greater the amplitude response changes, the greater will be the phase response changes. These changes in amplitude and phase are simply another form of DISTORTION, and the greater the distortion, the more likely we are to HEAR it. For example, when the crystal filters in the K2 are aligned for narrow SSB bandwidth, the amplitude response is QUITE bumpy, and the resulting phase distortion makes it hard to listen to. Now, it is POSSIBLE to detect a single frequency and reproduce it, then carefully add it precisely equal in amplitude and 180 degrees out of phase with the interfering signal without adding distortion. I don't know what method(s) Elecraft is using. Another point. NO audio stage is ideal -- there is SOME distortion, which consists of harmonics and even intermod products -- and a strong heterodyne can produce fairly strong harmonics. If the fundamental is there, it MASKS the harmonics (within our ear/brain) so that we don't hear them, but if the fundamental is removed, they can be quite audible. Audio engineers have learned to recognize various kinds of distortion products by listening to the distortion output of a distortion analyzer, which is essentially a notch filter. Bottom line -- ALL notch filters have audible artifacts. I use the notch only when I need it, and leave it off when I don't. 73, Jim Brown 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
