I started tracking radiosondes by an accident fall last year. I was randomly tuning my trusty 'ol RTL2832U SDR at night when I came across signals I've never heard before. A quick Google search revealed what it was all about then 5 minutes later, SondeMonitor was running. Then of course came the idea of catching one, so I got him onboard. The rest is history.
My QTH is not at the best location, as I'm in the middle of a valley. I use a 2m/70cm collinear antenna to track sondes.