The factory preamp was never meant to be used in the repeater configuration. It was primarily for mobiles.
I was checking the tuning on my duplexers for the 147.225 repeater after noticing some desense on with the service monitor. I had something like 99 watts going into the duplexers (sinclair Q-202g) and about 85 coming out. I thought, WOW! This cannot be right. Sure enough they were aparently mis-tuned. I switched the service monitor into the tracking gen mode and began. The rx side was pretty close and when I got done I had a -85db or so notch at 147.225mhz. All I had to do was move the ol' notches with the little caps next to the connector. The pass at 147.825 looked good, about -1.5db or so. Moved over to the TX side (low pass) and the notches were off. A good bit off in fact. So I startes tuning them to where they needed to be and all I could get was about -65db or so. What gives?!? Oh no, I thought. I am gonna have to spin the loops! EGAD!!! I hate doing that. Oh well, here goes nothing. I isolated the first jug and began spinning. I ended up getting it (one jug) down to about -31db. The other side were in the -35db or more area. Try as I may the -31db per can was about as good as I could get. Whith both cans together I get a -79db notch on the 147.825 rx frequency with about -1.4 db on the pass. Is this adequate for a MASTR II with the factory preamp? The desense is pretty much gone now. I think if I spent a little more time I could probably get the notch a little closer to the -85db that I got on the other pair on the high pass rx side, but I am not sure it is worth the effort. What do you thing guys??? 73 de N5NPO
