This is one of the most difficult thing for new digital ops to understand, and determine where the signal should be on the waterfall. I call the best spot ":sweet spot". Your rig will probably copy a signal just about any place across the waterfall, as long as its width is somewhere around 3 kc. If you spread it out any more than that, you probably wont get much signal at the edges.
More important, after you know you can receive well, is : Where should my transmit be? Thats where the sweet spot comes in. Select a quite band (maybe one where the props are not even in). Click on the extreme left (or right) side of the waterfall , set your rigs output for 10 or so watts, and then hit the transmit button. See what your rigs output wattage is. It will probably be very low, if you can see anything there at all. Remember, what you are transmitting is the audio from your computer. Deactivate the computers transmit, move your waterfall marker up 100 cycles (USING THE MOUSE TO CLICK ON THE WATERFALL SPOT - DO NOT MOVE YOUR RIGS VFO KNOB DURING THIS WHOLE PROCESS). Again hit transmit and see what your wattage output is. Again, turn the transmit off. Move up 100 cycles more and transmit again. Continue this testing completely across the whole bandwidth of the waterfall. What you will observe is that the transmit power goes from almost nil, curving up to a solid 10 watts, and slowly down to nil again. Once this is done, you can see where the audio output of the computer has driven the rig to its best output power. In the middle of this 10 watt output space, is where you can call your sweet spot. That is where I set my "offset" in the software. This way, when someone spots a station on: say- 14.0723, and you click on his spot, your rig will qsy to a freq, wherein its freq PLUS THE WATERFALL AUDIO will set YOUR receive waterfall marker, smack dab on top of his signal. After all, thats what we are looking for isnt it? I just hate it when I see someone spot 14.070 or 14.069. I immediately figure the spotter has no idea how this works (unless of course the spotted station is REALLY on that freq. I have run some 6 different computers on digital modes here in the station, and that sweet spot usually has been within 800 cycle - up to 1.5 KC. Each will be slightly different. If it comes out as 832, then I select 1 KC. If its near 1.4 kc, then I would select 1.5 (still within the top of the curve during the above test. That way, I can quickly figure out, in my head, what is going on. Mostly I dont need to figure anything out. Right now, my sweet spot (middle of the curve) is 1.089kc, so I have selected 1 KC as my offset. I immediately know, that if someone spots 14.07256 as a PSK freq, I can either simply click on his spot, and my rig will be on 14.071256, or I can reach up land put that freq manually on my VFO. I can also simply set my rig on 14.070 and observe all the siganls from that freq, up to approximately 14.073. I can click on any of them, and copy. If I want to work one of them, I his the proper button on my screen, which places that signal exactly 1KC away from the edge of the screen (the sweet spot). My rig QSYs to the proper freq (1KC away) and I call the station. So - No - dead center is not exactly what you want- unless you have a 3kc wide waterfall display, and your sweet spot is 1.5 KC, but you have probably made a pretty good guess - just getting there a different way. Using a straight 1KC or 1.5 KC makes it easier to think in "math". All of this is also contingent with how your receiver works too. I use a wideband receive filter, because I use WinWarbler software which has the great capability of multiple signal copy. In other words the software can actually copy EVERY signal across the waterfall, at one time. Much easier when you are looking for DX stations you havent worked before. You want to set that sweet spot, in your receiver passband, but that is another story altogether. If the above method works (and many have said it does) just go with it. Danny