Hi Ray - Yep it's true...This can become a Time Sink! I can receive them out to 50+ miles with a simple 6" 450 mc DIY ground plane on the roof driving my multimode receiver. No preamp or other antenna gain necessary. (I remember that big dish in the Fair catalogs!)
It's interesting to see their path and the predicted landing spot converge with the actual landing spot as reported by GPS. These RS-41's use around 9 GPS birds for very accurate X,Y, Z spatial coordinates and speed over the ground plus rise/fall rates. The sondes transmits all this info to ground stations, then to the Internet. It's crazy cold up there but then begins to get warmer higher up....
You can go retrieve them if you like, Youtube videos on simple reprogramming them to 450 mc ham usage...
I've not looked into decoding the data but there are methods online. The data seems to be NFM in bursts every second.
I can often see the ones launched from OAK as they fly over my area at around 30,000 feet on their way up. Binoculars help. At altitude they can be 20' in diameter. Sondehub.org shows their azimuth and elevation from your home too, pretty easy to acquire. I watched one burst awhile back. It was over 100K feet and they are apparently lined with talcum powder - made a very noticeable white puff but the parachutes are pretty tiny.... Fun!
Tim
N6CC