Fw: Signals not as they appear (continues)
From: VR2BrettGraham <vr2bg@...>;
Subject: Signals not as they appear (continues)
Sent: Sun, Jul 29, 2012 2:48:19 AM
What is the mechanism behind the spurious response at F+/-sample rate where F is slightly beyond Fc+/-(sample rate/2)?
Or in other words, what causes signals just a couple of kc below the bottom of the waterfall to appear a couple of kc below the top of the waterfall (and vice versa)?
Is there any way to reduce this spurious response? It doesn't appear to pervert the spectrum like I/Q imbalance does to Fc+/-x, so now knowing there is this other spurious response I have to wonder if the signals out towards the edges of the waterfall are really there. The signals that appear part on one edge of the waterfall & part on the other (straddling the edges of the waterfall) are easy to identify & disregard as spurious responses - the rest, well, maybe they are & maybe they are not...