[Elecraft] K3 RX Equalizer

[Jim Brown]

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