(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.)
You should get assistance the first time you do this procedure.
Open a set up file that contains the observe and decoupling frequencies which you will be using during spectrum collection (ie. H1setup, C13setup). Go to the probe interface, (the module on the floor next to the magnet). If the observe frequency is H-1, move the cable at the HB (high band) Probe port to the Tune port. For any observe frequency other than H-1, move the cable at the LB (low band) Probe port to the Tune port. You may need to insert a capacitor into the probe. The capacitor that should be used depends on the observe frequency. See Table 13.6 on p. 13-21 of the GN-SERIES USERS' MANUAL. The manual is located on the bookshelf in front of the GN-300 console. The capacitors are located at the bottom of the right door of the right console cabinet. Go back to the keyboard.
Move the cursor to the Console button and click the MB to open the Console window. Move the cursor to the TUNE button and click to start the tune routine. Return to the magnet and find probe capacitor adjusters which are located at the bottom of the probe. Adjust the probe match capacitor of the channel that you are tuning so that the bottom of the tuning dip is as low as possible on the screen. Next adjust the tune capacitor so that the dip is centered on the vertical black line in the middle of the screen. If large changes were made, repeat the tune and match adjustments.
If you will observe a nucleus other than H-1 and will use the decoupler channel, you should tune the decoupler channel by using the following procedure. Open the Dashboard window. Set the Obs Freq to be the same value as the F2 freq. Open the Console window and then the TUNE window. Adjust the H-1 or decoupler tune and match capacitors so that the tuning dip is positioned horizontally and vertically as described above. Exit the Console window and reset the Obs Freq to its initial value. This can be done by closing the file without saving changes and then opening it again.