I have to start off by saying that I am also just a casual ADS-B enthusiast. My dongle came with a mini mag mount antenna (as do most dongles) and I stuck it on the window sill of the north-facing window in my shack. My objective was to just get all of the pieces to play together (the dongle, computer and software) and then I would look into getting a "real" antenna tuned for 1090 MHz one day. It has been a year and a half and I am still using the mini mag mount!
Using the mini mag mount, here is a typical day:
I live where the red arrow is pointing and the plane in the red circle is just over 200 miles away! I could get a better antenna, but at some point, this nasty thing called the curvature of the earth comes into play. I can see planes headed for O'Hare, but once they drop below a certain altitude they fall off the screen and no antenna can account for this. Even if I put an antenna 15-20' higher, that would not buy me significantly more range.
I have been thinking about getting (making?) an antenna to put above the roof line of the house but about all that would do is show me planes in a 360° radius instead of just the ones to the north.
I do like that antenna in your picture frazpo. I know Google® is my friend, but could you post a link to the plans for that antenna? It would be most appreciated.