After figuring out how to find a convex hull for my airplane data, I went back to see how much the range has varied over time. Here's a timeline that shows the daily observations on top, and the area of the daily convex hull on the bottom:
I've had a few changes to my RTL setup over the last few years that have had an impact on range. I've had basically three different configurations in the last two years: (1) an initial version connecting a NooElec RTL-SDR straight to the antenna, (2) an updated version that added a FlightAware filter between the NooElec and the antenna, and (3) a new version that uses a FlightAware Pro USB stick that has the filter built into it. Here's how big the convex hulls were for the data points collected in each day for the three settings:
In general, the filtering does seem to boost my range a good bit. The FlightAware Pro USB stick also seems to do better than a generic tuner that's plugged into an external filter. To be fair though- there were other things that changed in my setup over the years that may be skewing some of these numbers. At some point I inserted a splitter into my setup so I could also route the antenna to a USB DVB tuner. I think that explains the drop you see in the middle of the second setup (ignore the two gap periods- those were because the recorder wasn't running full days).
Now that my setup is a little more setup, I'd like to capture some data and then see how well my range corresponds with things like the weather (sounds like a fun science project for the kids).