At 09:36 AM 8/19/2006, you wrote: >A friend of mine asked me a couple of questions, below, and I thought >someone on the list more tech than I could answer them... > >I sent him an audio recording of a CW signal that I had recorded using the >25Hz filter which prompted his question, below. > >I mentioned to him that the audio sounds really round with this filter and >perhaps that's what he's describing. > >Any takers? > >Mark
<some snipping...> A couple things to bear in mind... 1) The transmitted bandwidth of the CW signal may well be wider than the filter you use to receive it. 2) The envelope of a baseband CW signal isn't a nice sine wave, so approximating rise and fall times with 1/bandwidth isn't necessarily valid but most important: 3) The optimum receive bandwidth isn't necessarily the signal bandwidth. You may decide to receive with a narrower bandwidth (which reduces an adjacent signal or total noise power), and improve the actual (or more important, the perceived) SNR. Your ear and brain are pretty good at demodulating a CW signal that is received with a very narrow (potentially ringing) filter. I seem to recall seeing, somewhere, a few years ago, a very elegant analysis of the actual spectrum of actual CW and some work on optimum filters. Jim, W6RMK _______________________________________________ FlexRadio mailing list [email protected] http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
