I remember seeing something about a year ago that was smoked see thru and round that went over ur antenna outside and they advertised it used military technology, I just googled the topic and came up with nothing tho, sorry.
Get a *GOOD* low noise pre-amp. NOT some cheap trash. Get hooked up with a radio nut (Amature radio (Ham) operator). Try a google search on something like "GaAs FET pre-amps". That should get ya going. Most will have adjustable gains.