You may get more responses posting in the general LabVIEW forums. This forum is dedicated to National Instruments High-Speed Digitizer products. That said, however...
You did not give us much information to work with. We need to know how you are connecting to the ADC. A quick look at the AD9643 shows it is a fairly standard ADC with dual converters, but a single parallel output. You will need a lot of high-speed parallel digital I/O to drive this. You may have already solved this issue. If you have not, consider a good high-speed digital I/O board. National Instruments sells several.
If your only problem is plotting on a log scale, LabVIEW graphs can be changed to logarithmic scaling by right clicking on the axis and selecting Mapping»Logarithmic. This will also modify the labels and tick marks appropriately. You can use property nodes of the graph to switch this programmatically.
Hopefully this somewhat answered your question. When you have further questions, let us know.