I have some experience with the 800Mhz version of that. This style preamp was typically used to overcome
a receive system total insertion loss's and were aligned such that the total receive gain was only slightly to
overcome the total insertion loss. To do that you have to open up the unit and make adjustments while
using a tracking generator on the input vs the ouput.
http://batboard.batlabs.com/viewtopic.php?t=53862