The subject of single field strength data has been discussed numerous times on this mailing list. It is recommended to read previous responses to questions relating to single field strength data, and look the other messages in those threads. You will find these discussions quite informative and highly detailed:
# Danyun Zeng: http://thread.gmane.org/gmane.science.nmr.relax.user/1800
# Sean Leo Moro: http://thread.gmane.org/gmane.science.nmr.relax.user/1787/focus=1788
# Martin Ballaschk: http://thread.gmane.org/gmane.science.nmr.relax.user/1409/focus=1438