Oops I meant to say: "Ringing is a function of the bandwidth and only SLIGHTLY affected by the type of filter."
-----Original Message----- From: Ron D'Eau Claire [mailto:[EMAIL PROTECTED] Sent: Friday, November 30, 2007 8:52 PM To: 'elecraft@mailman.qth.net' Subject: RE: [Elecraft] K3 filters Any filter will produce "ringing" when the bandwidth is too small. Ringing is a function of the bandwidth and only affected by the type of filter. In some filter designs it's possible for some elements of the filter to have such a high Q they ring even though the overall filter bandpass is not that small, but that's a aberration in the filter design. Ringing typically occurs when the bandwidth at either the transmitter or receiver is restricted too much to allow the CW sidebands to pass through. Of course, the sidebands on a CW signal are the frequencies represented by the rise and fall of each CW element. If the bandwidth isn't sufficient to pass them, the element is stretched out in time as the amplitude decays, just like the amplitude of a bell decays after the bell was stuck. That's what we call "ringing". Ron AC7AC -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Alan Bloom Sent: Friday, November 30, 2007 1:47 PM To: Darwin, Keith Cc: elecraft@mailman.qth.net Subject: RE: [Elecraft] K3 filters For the same passband ripple and bandwidth I think more poles pretty much invariably means more ringing. By the way, many people think that DSP-based filters don't ring. Actually, a digital filter's impulse response, measured at say the half-power point, is pretty comparable to an analog (e.g. cyrstal) filter with the same ripple and bandwidth. However, the ringing from a digital FIR (finite impulse response) filter eventually drops all the way to zero, while an IIR (e.g. analog) filter theoretically rings forever. Since human sound perception tends to be logarithmic, the ringing _sounds_ longer with the analog filter. Al N1AL _______________________________________________ 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
