If a digimode decoder is good enough then it can only be hurt, not helped,
by additional pre-filtering. This is because in the presence of noise there
is a statistical limit ("optimal detection") to how faithfully you can
extract the desired signal. Which is why I've said before: If the dual
filter were such a great idea, it would already be written into the
software for your RTTY decoder, at least as part of one of the decode
methods you can select. It's possible that some less capable decoders will
be helped by it, but if it doesn't help you then don't use it. I use MMTTY
and have not noticed it to help. Never hurts to try, though. There are so
many varied impairments to over-the-air signals that no simple collection
of decoders will have one that's optimal in every case.73, Carl WS7L On Monday, January 6, 2014, Joe Subich, W4TV wrote: > > That information is based on input from K7AY (cocoaModem) and G3YYD > (2-Tone). The software decoders do a better job when supplied with > audio at least 400 Hz wide without frequency shaping from the IF (DSP) > filter. The Dual Band Pass filters in general introduce significant > phase delays and amplitude inequality which results in poorer decoding > accuracy in modern FFT based demodulators - although the frequency > shaping may be of value in older amplitude (filter/detector) style > demodulators. > > > 73, > > ... Joe, W4TV ______________________________________________________________ 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
