[Elecraft] k3/psk on laptop

[Jim Brown]

On Wed, 11 Jun 2008 13:34:21 -0400, Joe Subich, W4TV wrote:

>BTW, to answer Ed's question ... even a limited dynamic range 
>is generally satisfactory for "narrow bandwidth" operation. 

You're exactly right, Joe, and this is quite important. Signal to 
noise measurements are broadband, but RTTY and PSK decoders are 
looking VERY narrowband. The noise in the narrow bandwidth of good 
PSK and RTTY decoders is a tiny fraction of the measured broadband 
noise, but the signal level can be the full output of the RX. It's 
the same sort of advantage that an RX with good IF filtering 
enjoys. 

While I haven't done studies on the subject, I'd bet that 
amplitude distortion and phase distortion are of much greater 
signifcance. And phase distortion mostly occurs in the IF of the 
radios as a byproduct of the filters, so I would expect radios 
with better filters to be better RTTY and PSK performers. These 
factors certainly ARE a major contributor to speech 
intelligibility, which is why the K2 is not wonderful in narrow 
SSB modes -- the amplitude and phase response of the stagger-tuned 
filters looks like the cut-through of a mountain range! 

Ed -- do you have any anecodotal or other experience on that?

73,

Jim Brown K9YC