Update: I received the antenna and cable today.. Wow.. what a difference it's made. Not only are aircraft NOT timing out nearly as often as before, but I'm picking up 2-3 times more aircraft, and at a distance of around 190 nautical miles at high altitude, and for the first time, i'm seeing aircraft on the 'ground'.
To say I'm pleased with the antenna is an understatement. It's like comparing night and day. The best part is, the aircraft aren't disappearing after 30 seconds like before.