[Elecraft] K3 and PSK31 Data Mode and ESSB

[Jim Brown]

On Tue, 24 Mar 2009 08:28:57 +0000, David Woolley (E.L) wrote:

>Doing so only acts as a roofing filter.  With a good enough sound card 
>and good enough algorithms, the terminal program ought to be able to 
>eliminate the interference as well as using a narrow filter in the K3 DSP.

I disagree, for two reasons. 

1) IDEALLY, the soundcard should be good enough to reject interfering 
SIGNALS, but computer sound cards are notoriously poor. Thus, a good 
roofing filter for the sound card (in the form of a narrow IF, and even a 
good audio filter) is a very good thing. 

2) Noise that appears anywhere in the passband is broadband in the audio 
spectrum, and raises the overall noise level at the sound card. When we 
improve that signal to noise ratio without degrading the magnitude and 
phase response for the desired signal, the soundcard has a better chance of 
decoding a weak signal. 

73,

Jim Brown K9YC