On 12/29/2017 12:52 PM, Walter Underwood wrote:
That would suggest that using hi-cut is a better choice than RX EQ for cutting high frequency hiss. The ultimate rejection for hi-cut is greater than the max RX EQ cut, right?
The smarter guys writing software for digital modes have finally learned what we learned in the world of pro audio at least 40 years ago -- filters introduce phase shift, and both our ears decoding speech and software decoding digital signals don't like the time smear that comes with it. In general, the steeper the amplitude response, the more phase shift occurs in the passband.
Current recommendations for RTTY decoding is 500 Hz bandwidth, and this is echoed by guys who regularly WIN major RTTY contests. Indeed, the double-hump RTTY filter built into firmware for K3/K3S/KX2/KX3 is no longer recommended. K1JT urges WSJT-X users to run the receiver IF wide open and let the software do the discrimination between signals. I set my K3 IF to its widest settings.
The same thing happens when narrow filters are used on CW in the presence of static -- the crashes ring the filters, defeating the purpose of reducing overall noise level. K3/K3S firmware has some specially shaped filters to minimize this effect. RTFM to learn about them.
73, Jim K9YC 73, Jim K9YC ______________________________________________________________ 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 Message delivered to [email protected]
