(These instructions assume you are familiar with basic Macintosh procedures, if you are not, see a Macintosh manual or the tutorial which is on most Macintosh computers. Throughout the following, MB means mouse button.)
If you would like to get the flattest baseline possible do the following after locking, shimming, and RCVR gain adjustment and before spectrum acquisition.
Go to the Console window and then to the FREQ window. If the box below Filter type: does not say Bessel, move the cursor to the box, hold down the MB and drag to Bessel, then release the MB. Open the pulse sequence window. Find the acquisition event by looking down the leftmost column and finding ACQ, then look to the right of ACQ for the ACQ icon (it looks like a FID). Move the cursor to the EVENT # row (near the top of the window) in the ACQ column, stay in this row and move to the event column just before the ACQ event column. Click the MB and set the Delay value to (0.7 x Dwell 1D). Collect a single scan, process and adjust the phase. Use the up and/or down keyboard arrows to adjust the spectrum amplitude so that noise in the baseline is observable. Look at the baseline and notice if its level in the middle of the spectrum is higher or lower than the baseline level at the ends of the spectrum. Decrease the preacquisition Delay value if the middle of the baseline is at a higher level than the ends, increase the Delay value if the middle of the baseline is at a lower level than the ends. Continue to adjust the preacquisition Delay until the flattest baseline has been obtained.