At the moment I need things fairly quiet to be able to copy well so for now narrow filters are the cats meow for me but maybe someday I'll graduate to wider filters. I prefer the sound of wider but... for me narrow aids in copy for me.
~Brett On Sun, 2009-08-09 at 07:31 -0700, Ron D'Eau Claire wrote: > Brett wrote: > I'd never had a rig capable of going lower than 500Hz till I got the K3 > and really found myself quite annoyed at times when the noise was high > and I really necked the filter down. > > ---------------------------------- > > You've discovered exactly why many of us avoid narrow filters whenever > possible. Our brains are much better at recognizing a CW signal in broadband > noise than in narrow-band noise. The same is true for digital noise > reduction. > > At very narrow bandwidths the filter also modifies the CW signal, softening > the keying to make it sound more and more like noise rather than a keyed > signal. Both the tx at the far end and your receiver must allow enough of > the CW sidebands through to hear clean, sharp keying transitions. That takes > some reasonable bandwidth. The faster the CW the more bandwidth is needed. > Some people don't want to hear any keying transitions (what, when excessive, > we call "clicks") at all only a few Hz from the carrier, but that really > compromises readability. Our brains hear those sidebands and help us detect > the signal from the noise, and the sidebands must be passed through your > receive filter. > > The first step to using wider bandwidths is to learn to copy CW when other > signals are present, just like learning to listen to one conversation in a > crowded room even though you can hear others talking all around you. > > When another signal within the passband is sufficiently loud to be a serious > distraction, sort of like trying to hear a quiet voice with someone else > shouting in your ear, a notch filter is preferred over narrowing the > bandwidth. All the notch need to is reduce the offendingly-loud signal > enough to make it less troublesome. Poking a narrow 'hole' in the noise > doesn't cause the problems a narrow filter does. > > Optionally, you can often tune the rx off frequency just a bit to push a > 'loudmouth' off the edge of the filter bandpass while keeping the desired > signal within the bandpass. > > It takes practice, but it's a skill worth having on a crowded band. Probably > 90% of my brass pounding is done at a bandwidth of 1 kHz or wider. > > Ron AC7AC > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
