You all are very kind helping me learn this. Thank you so much for the patience!
I will certainly attempt to calibrate to the ends of the SMA connectors and re-visit this issue.
In thinking about this filter coupler and the termination issue, I could experiment with simply placing a termination resistor on the end to ground without soldering, but pressing down on it with a non-metallic tool and see what that does. I guess another possibility is to just place a circulator at the input, and I just happen to have a couple of decent 1.9-2.1GHz circulators.
As for the 2sc2150's noise figure, here's what I found in a 1995 NEC semiconductor selection guide...
Thanks for the lunchtime reading on the HP Journal - I love browsing those!